[LibCall] Infer nocallback for libcalls #135173

dtcxzyw · 2025-04-10T13:17:56Z

This patch adds nocallback attributes for string/math libcalls. It allows FuncAttributor to infer norecurse more precisely and encourages more aggressive global optimization.

llvmbot · 2025-04-10T17:08:29Z

@llvm/pr-subscribers-backend-x86

Author: Yingwei Zheng (dtcxzyw)

Changes

This patch adds nocallback attributes for most of libcalls (except for exit/terminate/qsort/signal/...). It allows FuncAttributor to infer norecurse more precisely and encourages more aggressive global optimization.

Patch is 53.30 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/135173.diff

12 Files Affected:

(modified) llvm/lib/Transforms/Utils/BuildLibCalls.cpp (+122-1)
(modified) llvm/test/CodeGen/X86/no-plt-libcalls.ll (+1-1)
(modified) llvm/test/Transforms/InferFunctionAttrs/annotate.ll (+34-33)
(modified) llvm/test/Transforms/InferFunctionAttrs/readonly_and_writeonly.ll (+1-1)
(modified) llvm/test/Transforms/InstCombine/printf-2.ll (+1-1)
(modified) llvm/test/Transforms/LICM/strlen.ll (+1-1)
(modified) llvm/test/Transforms/LoopIdiom/basic.ll (+1-2)
(modified) llvm/test/Transforms/LoopIdiom/memset-pattern-tbaa.ll (+1-1)
(modified) llvm/test/Transforms/LoopIdiom/struct_pattern.ll (+1-1)
(modified) llvm/test/Transforms/LoopIdiom/unroll-custom-dl.ll (+1-1)
(modified) llvm/test/Transforms/LoopIdiom/unroll.ll (+1-1)
(modified) llvm/test/Transforms/PreISelIntrinsicLowering/X86/memset-pattern.ll (+1-1)

diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
index 24eefc91117b4..88704d689c3b1 100644
--- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -47,6 +47,7 @@ STATISTIC(
     NumWriteArgumentMemOrErrnoMemOnly,
     "Number of functions inferred as memory(argmem: write, errnomem: write)");
 STATISTIC(NumNoUnwind, "Number of functions inferred as nounwind");
+STATISTIC(NumNoCallback, "Number of functions inferred as nocallback");
 STATISTIC(NumNoCapture, "Number of arguments inferred as nocapture");
 STATISTIC(NumWriteOnlyArg, "Number of arguments inferred as writeonly");
 STATISTIC(NumReadOnlyArg, "Number of arguments inferred as readonly");
@@ -148,6 +149,14 @@ static bool setDoesNotThrow(Function &F) {
   return true;
 }
 
+static bool setDoesNotCallback(Function &F) {
+  if (F.hasFnAttribute(Attribute::NoCallback))
+    return false;
+  F.addFnAttr(Attribute::NoCallback);
+  ++NumNoCallback;
+  return true;
+}
+
 static bool setRetDoesNotAlias(Function &F) {
   if (F.hasRetAttribute(Attribute::NoAlias))
     return false;
@@ -322,6 +331,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_wcslen:
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
@@ -331,6 +341,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     break;
   case LibFunc_strtol:
@@ -341,6 +352,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_strtold:
   case LibFunc_strtoull:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 0);
@@ -349,6 +361,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_strncat:
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setReturnedArg(F, 0);
     Changed |= setDoesNotCapture(F, 1);
@@ -364,6 +377,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_stpncpy:
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyWritesMemory(F, 0);
@@ -373,6 +387,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     break;
   case LibFunc_strxfrm:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
@@ -383,6 +398,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_strncmp:     // 0,1
   case LibFunc_strcspn:     // 0,1
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setOnlyReadsMemory(F);
@@ -396,6 +412,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     // global memory.
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
@@ -405,12 +422,14 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_strtok:
   case LibFunc_strtok_r:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 1);
@@ -418,6 +437,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_scanf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
     break;
@@ -425,6 +445,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_setvbuf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_strndup:
@@ -434,6 +455,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setAllocFamily(F, "malloc");
     Changed |= setOnlyAccessesInaccessibleMemOrArgMem(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
@@ -443,6 +465,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_statvfs:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 0);
@@ -450,6 +473,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_sscanf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 0);
@@ -458,6 +482,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_sprintf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotAlias(F, 0);
     Changed |= setOnlyWritesMemory(F, 0);
@@ -467,6 +492,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_snprintf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotAlias(F, 0);
     Changed |= setOnlyWritesMemory(F, 0);
@@ -476,6 +502,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_setitimer:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setDoesNotCapture(F, 2);
@@ -483,6 +510,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     break;
   case LibFunc_system:
     // May throw; "system" is a valid pthread cancellation point.
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
@@ -502,6 +530,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesInaccessibleMemory(F);
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     break;
@@ -509,6 +538,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
@@ -516,6 +546,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_memchr:
   case LibFunc_memrchr:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setWillReturn(F);
@@ -524,6 +555,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_modff:
   case LibFunc_modfl:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyWritesMemory(F);
@@ -531,6 +563,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     break;
   case LibFunc_memcpy:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotAlias(F, 0);
@@ -542,6 +575,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     break;
   case LibFunc_memmove:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setReturnedArg(F, 0);
@@ -555,6 +589,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     [[fallthrough]];
   case LibFunc_memcpy_chk:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setDoesNotAlias(F, 0);
     Changed |= setOnlyWritesMemory(F, 0);
@@ -571,18 +606,21 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesInaccessibleMemory(F);
     Changed |= setRetNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     break;
   case LibFunc_mkdir:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
     break;
   case LibFunc_mktime:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
@@ -597,6 +635,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesInaccessibleMemOrArgMem(F);
     Changed |= setRetNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
@@ -610,6 +649,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesInaccessibleMemOrArgMem(F);
     Changed |= setRetNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
@@ -618,12 +658,14 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     break;
   case LibFunc_read:
     // May throw; "read" is a valid pthread cancellation point.
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_rewind:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_rmdir:
@@ -631,12 +673,14 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_realpath:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
     break;
   case LibFunc_rename:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 0);
@@ -645,18 +689,21 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_readlink:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 0);
     break;
   case LibFunc_write:
     // May throw; "write" is a valid pthread cancellation point.
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 1);
     break;
   case LibFunc_bcopy:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
@@ -666,6 +713,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     break;
   case LibFunc_bcmp:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setWillReturn(F);
@@ -674,6 +722,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     break;
   case LibFunc_bzero:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
@@ -688,6 +737,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesInaccessibleMemory(F);
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     break;
@@ -695,6 +745,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_chown:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
     break;
@@ -703,6 +754,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_closedir:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_atoi:
@@ -710,6 +762,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_atof:
   case LibFunc_atoll:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
@@ -717,12 +770,14 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_access:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
     break;
   case LibFunc_fopen:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
@@ -732,6 +787,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fdopen:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 1);
@@ -739,6 +795,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_feof:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_free:
@@ -750,6 +807,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesInaccessibleMemOrArgMem(F);
     Changed |= setArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
@@ -768,11 +826,13 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_ftrylockfile:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_ferror:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F);
     break;
@@ -781,12 +841,14 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fstat:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_frexp:
   case LibFunc_frexpf:
   case LibFunc_frexpl:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyWritesMemory(F);
@@ -795,12 +857,14 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fstatvfs:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_fgets:
   case LibFunc_fgets_unlocked:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 2);
     Changed |= setOnlyWritesMemory(F, 0);
     break;
@@ -808,6 +872,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fread_unlocked:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 3);
     Changed |= setOnlyWritesMemory(F, 0);
@@ -816,6 +881,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fwrite_unlocked:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 3);
     Changed |= setOnlyReadsMemory(F, 0);
@@ -824,6 +890,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fputs_unlocked:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 0);
@@ -832,6 +899,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fprintf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 1);
@@ -839,27 +907,32 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fgetpos:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_getc:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_getlogin_r:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_getc_unlocked:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_getenv:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
@@ -868,37 +941,44 @@ bool llvm::inferNonMandatoryLibFuncAttr...
[truncated]

llvmbot · 2025-04-10T17:08:29Z

@llvm/pr-subscribers-llvm-transforms

Author: Yingwei Zheng (dtcxzyw)

Changes

This patch adds nocallback attributes for most of libcalls (except for exit/terminate/qsort/signal/...). It allows FuncAttributor to infer norecurse more precisely and encourages more aggressive global optimization.

Patch is 53.30 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/135173.diff

12 Files Affected:

(modified) llvm/lib/Transforms/Utils/BuildLibCalls.cpp (+122-1)
(modified) llvm/test/CodeGen/X86/no-plt-libcalls.ll (+1-1)
(modified) llvm/test/Transforms/InferFunctionAttrs/annotate.ll (+34-33)
(modified) llvm/test/Transforms/InferFunctionAttrs/readonly_and_writeonly.ll (+1-1)
(modified) llvm/test/Transforms/InstCombine/printf-2.ll (+1-1)
(modified) llvm/test/Transforms/LICM/strlen.ll (+1-1)
(modified) llvm/test/Transforms/LoopIdiom/basic.ll (+1-2)
(modified) llvm/test/Transforms/LoopIdiom/memset-pattern-tbaa.ll (+1-1)
(modified) llvm/test/Transforms/LoopIdiom/struct_pattern.ll (+1-1)
(modified) llvm/test/Transforms/LoopIdiom/unroll-custom-dl.ll (+1-1)
(modified) llvm/test/Transforms/LoopIdiom/unroll.ll (+1-1)
(modified) llvm/test/Transforms/PreISelIntrinsicLowering/X86/memset-pattern.ll (+1-1)

diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
index 24eefc91117b4..88704d689c3b1 100644
--- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -47,6 +47,7 @@ STATISTIC(
     NumWriteArgumentMemOrErrnoMemOnly,
     "Number of functions inferred as memory(argmem: write, errnomem: write)");
 STATISTIC(NumNoUnwind, "Number of functions inferred as nounwind");
+STATISTIC(NumNoCallback, "Number of functions inferred as nocallback");
 STATISTIC(NumNoCapture, "Number of arguments inferred as nocapture");
 STATISTIC(NumWriteOnlyArg, "Number of arguments inferred as writeonly");
 STATISTIC(NumReadOnlyArg, "Number of arguments inferred as readonly");
@@ -148,6 +149,14 @@ static bool setDoesNotThrow(Function &F) {
   return true;
 }
 
+static bool setDoesNotCallback(Function &F) {
+  if (F.hasFnAttribute(Attribute::NoCallback))
+    return false;
+  F.addFnAttr(Attribute::NoCallback);
+  ++NumNoCallback;
+  return true;
+}
+
 static bool setRetDoesNotAlias(Function &F) {
   if (F.hasRetAttribute(Attribute::NoAlias))
     return false;
@@ -322,6 +331,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_wcslen:
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
@@ -331,6 +341,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     break;
   case LibFunc_strtol:
@@ -341,6 +352,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_strtold:
   case LibFunc_strtoull:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 0);
@@ -349,6 +361,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_strncat:
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setReturnedArg(F, 0);
     Changed |= setDoesNotCapture(F, 1);
@@ -364,6 +377,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_stpncpy:
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyWritesMemory(F, 0);
@@ -373,6 +387,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     break;
   case LibFunc_strxfrm:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
@@ -383,6 +398,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_strncmp:     // 0,1
   case LibFunc_strcspn:     // 0,1
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setOnlyReadsMemory(F);
@@ -396,6 +412,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     // global memory.
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
@@ -405,12 +422,14 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_strtok:
   case LibFunc_strtok_r:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 1);
@@ -418,6 +437,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_scanf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
     break;
@@ -425,6 +445,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_setvbuf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_strndup:
@@ -434,6 +455,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setAllocFamily(F, "malloc");
     Changed |= setOnlyAccessesInaccessibleMemOrArgMem(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
@@ -443,6 +465,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_statvfs:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 0);
@@ -450,6 +473,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_sscanf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 0);
@@ -458,6 +482,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_sprintf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotAlias(F, 0);
     Changed |= setOnlyWritesMemory(F, 0);
@@ -467,6 +492,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_snprintf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotAlias(F, 0);
     Changed |= setOnlyWritesMemory(F, 0);
@@ -476,6 +502,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_setitimer:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setDoesNotCapture(F, 2);
@@ -483,6 +510,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     break;
   case LibFunc_system:
     // May throw; "system" is a valid pthread cancellation point.
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
@@ -502,6 +530,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesInaccessibleMemory(F);
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     break;
@@ -509,6 +538,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
@@ -516,6 +546,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_memchr:
   case LibFunc_memrchr:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setWillReturn(F);
@@ -524,6 +555,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_modff:
   case LibFunc_modfl:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyWritesMemory(F);
@@ -531,6 +563,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     break;
   case LibFunc_memcpy:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotAlias(F, 0);
@@ -542,6 +575,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     break;
   case LibFunc_memmove:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setReturnedArg(F, 0);
@@ -555,6 +589,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     [[fallthrough]];
   case LibFunc_memcpy_chk:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setDoesNotAlias(F, 0);
     Changed |= setOnlyWritesMemory(F, 0);
@@ -571,18 +606,21 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesInaccessibleMemory(F);
     Changed |= setRetNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     break;
   case LibFunc_mkdir:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
     break;
   case LibFunc_mktime:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
@@ -597,6 +635,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesInaccessibleMemOrArgMem(F);
     Changed |= setRetNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
@@ -610,6 +649,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesInaccessibleMemOrArgMem(F);
     Changed |= setRetNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
@@ -618,12 +658,14 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     break;
   case LibFunc_read:
     // May throw; "read" is a valid pthread cancellation point.
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_rewind:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_rmdir:
@@ -631,12 +673,14 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_realpath:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
     break;
   case LibFunc_rename:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 0);
@@ -645,18 +689,21 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_readlink:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 0);
     break;
   case LibFunc_write:
     // May throw; "write" is a valid pthread cancellation point.
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 1);
     break;
   case LibFunc_bcopy:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
@@ -666,6 +713,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     break;
   case LibFunc_bcmp:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setWillReturn(F);
@@ -674,6 +722,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     break;
   case LibFunc_bzero:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
@@ -688,6 +737,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesInaccessibleMemory(F);
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setWillReturn(F);
     break;
@@ -695,6 +745,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_chown:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
     break;
@@ -703,6 +754,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_closedir:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_atoi:
@@ -710,6 +762,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_atof:
   case LibFunc_atoll:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
@@ -717,12 +770,14 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_access:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F, 0);
     break;
   case LibFunc_fopen:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
@@ -732,6 +787,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fdopen:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setRetDoesNotAlias(F);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 1);
@@ -739,6 +795,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_feof:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_free:
@@ -750,6 +807,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyAccessesInaccessibleMemOrArgMem(F);
     Changed |= setArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
@@ -768,11 +826,13 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_ftrylockfile:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_ferror:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setOnlyReadsMemory(F);
     break;
@@ -781,12 +841,14 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fstat:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_frexp:
   case LibFunc_frexpf:
   case LibFunc_frexpl:
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setWillReturn(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setOnlyWritesMemory(F);
@@ -795,12 +857,14 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fstatvfs:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_fgets:
   case LibFunc_fgets_unlocked:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 2);
     Changed |= setOnlyWritesMemory(F, 0);
     break;
@@ -808,6 +872,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fread_unlocked:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 3);
     Changed |= setOnlyWritesMemory(F, 0);
@@ -816,6 +881,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fwrite_unlocked:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 3);
     Changed |= setOnlyReadsMemory(F, 0);
@@ -824,6 +890,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fputs_unlocked:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 0);
@@ -832,6 +899,7 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fprintf:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setOnlyReadsMemory(F, 1);
@@ -839,27 +907,32 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_fgetpos:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_getc:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_getlogin_r:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_getc_unlocked:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
   case LibFunc_getenv:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
+    Changed |= setDoesNotCallback(F);
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotCapture(F, 0);
     break;
@@ -868,37 +941,44 @@ bool llvm::inferNonMandatoryLibFuncAttr...
[truncated]

antoniofrighetto

LGTM (glibc used to support malloc/free user hooks, but even in that case, I don't think it would be too much of an issue).

dtcxzyw · 2025-04-11T02:25:45Z

glibc used to support malloc/free user hooks, but even in that case, I don't think it would be too much of an issue

While GNU memory allocation hooks were deprecated in glibc 2.34, other memory allocators (e.g., mimalloc/jemalloc) still provide some kinds of callback mechanisms :(

nikic

At least a lot of the FS stuff here is wrong due to fopencookie.

llvm/lib/Transforms/Utils/BuildLibCalls.cpp

nikic

Generally, I'd be a lot more comfortable if this were limited to the "obvious" stuff (like memcmp not going to call back to user code) and skip everything syscall related.

llvm-ci · 2025-04-12T07:27:19Z

LLVM Buildbot has detected a new failure on builder openmp-s390x-linux running on systemz-1 while building llvm at step 6 "test-openmp".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/88/builds/10344

Here is the relevant piece of the build log for the reference

Step 6 (test-openmp) failure: test (failure)
******************** TEST 'libomp :: tasking/issue-94260-2.c' FAILED ********************
Exit Code: -11

Command Output (stdout):
--
# RUN: at line 1
/home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.build/./bin/clang -fopenmp   -I /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.build/runtimes/runtimes-bins/openmp/runtime/src -I /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.src/openmp/runtime/test -L /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.build/runtimes/runtimes-bins/openmp/runtime/src  -fno-omit-frame-pointer -mbackchain -I /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.src/openmp/runtime/test/ompt /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.src/openmp/runtime/test/tasking/issue-94260-2.c -o /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.build/runtimes/runtimes-bins/openmp/runtime/test/tasking/Output/issue-94260-2.c.tmp -lm -latomic && /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.build/runtimes/runtimes-bins/openmp/runtime/test/tasking/Output/issue-94260-2.c.tmp
# executed command: /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.build/./bin/clang -fopenmp -I /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.build/runtimes/runtimes-bins/openmp/runtime/src -I /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.src/openmp/runtime/test -L /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.build/runtimes/runtimes-bins/openmp/runtime/src -fno-omit-frame-pointer -mbackchain -I /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.src/openmp/runtime/test/ompt /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.src/openmp/runtime/test/tasking/issue-94260-2.c -o /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.build/runtimes/runtimes-bins/openmp/runtime/test/tasking/Output/issue-94260-2.c.tmp -lm -latomic
# executed command: /home/uweigand/sandbox/buildbot/openmp-s390x-linux/llvm.build/runtimes/runtimes-bins/openmp/runtime/test/tasking/Output/issue-94260-2.c.tmp
# note: command had no output on stdout or stderr
# error: command failed with exit status: -11

--

********************

This patch adds `nocallback` attributes for string/math libcalls. It allows FuncAttributor to infer `norecurse` more precisely and encourages more aggressive global optimization.

Infer nocallback for libcalls

3268bd6

This was referenced Apr 10, 2025

Task submission dtcxzyw/llvm-opt-benchmark#1312

Open

pre-commit: PR135173 dtcxzyw/llvm-opt-benchmark#2250

Closed

dtcxzyw requested review from nikic, antoniofrighetto and efriedma-quic April 10, 2025 17:07

dtcxzyw marked this pull request as ready for review April 10, 2025 17:07

llvmbot added backend:X86 llvm:instcombine llvm:transforms labels Apr 10, 2025

antoniofrighetto approved these changes Apr 10, 2025

View reviewed changes

[LibCall] Do not set nocallback for memory allocation functions

b47d587

nikic requested changes Apr 11, 2025

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nikic reviewed Apr 11, 2025

View reviewed changes

llvm/lib/Transforms/Utils/BuildLibCalls.cpp Outdated Show resolved Hide resolved

nikic reviewed Apr 11, 2025

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dtcxzyw added 2 commits April 12, 2025 00:19

[LibCall] Address review comments.

8fa5c03

[LibCall] Reduce test changes. NFC.

48d39bc

nikic approved these changes Apr 11, 2025

View reviewed changes

dtcxzyw merged commit 76e07d8 into llvm:main Apr 12, 2025
11 checks passed

dtcxzyw deleted the perf/nocallback branch April 12, 2025 07:11

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