[NFC][clang] Add ubsan-trap-merge.ll test to show absence of nomerge considered harmful #117657
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…considered harmful This testcase demonstrates that when nomerge is missing from ubsantrap intrinsics, they may be merged when inlining. This is based on the observation and testcase by Vitaly Buka in llvm#83470
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@llvm/pr-subscribers-mc @llvm/pr-subscribers-backend-x86 Author: Thurston Dang (thurstond) ChangesThis testcase demonstrates that when nomerge is missing from ubsantrap intrinsics, they may be merged when inlining. This is based on the observation and testcase by Vitaly Buka in #83470 Full diff: https://github.com/llvm/llvm-project/pull/117657.diff 1 Files Affected:
diff --git a/llvm/test/MC/X86/ubsan-trap-merge.ll b/llvm/test/MC/X86/ubsan-trap-merge.ll
new file mode 100644
index 00000000000000..b96c85473e5387
--- /dev/null
+++ b/llvm/test/MC/X86/ubsan-trap-merge.ll
@@ -0,0 +1,181 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -O3 -mtriple x86_64 -filetype asm -o - %s | FileCheck %s
+;
+; This test shows that ubsantrap can, in the absence of nomerge, be merged by
+; the backend into a single ud1 instruction (thus making debugging difficult).
+;
+; The LLVM IR was generated from clang/test/CodeGen/ubsan-trap-merge.c.
+;
+; ModuleID = '../clang/test/CodeGen/ubsan-trap-merge.c'
+source_filename = "../clang/test/CodeGen/ubsan-trap-merge.c"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Function Attrs: nounwind uwtable
+define dso_local range(i32 -2147483523, -2147483648) i32 @f(i32 noundef %x) local_unnamed_addr #0 {
+; CHECK-LABEL: f:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: addl $125, %edi
+; CHECK-NEXT: jo .LBB0_1
+; CHECK-NEXT: # %bb.2: # %cont
+; CHECK-NEXT: movl %edi, %eax
+; CHECK-NEXT: retq
+; CHECK-NEXT: .LBB0_1: # %trap
+; CHECK-NEXT: ud1l 2(%eax), %eax
+entry:
+ %0 = tail call { i32, i1 } @llvm.sadd.with.overflow.i32(i32 %x, i32 125), !nosanitize !5
+ %1 = extractvalue { i32, i1 } %0, 1, !nosanitize !5
+ br i1 %1, label %trap, label %cont, !nosanitize !5
+
+trap: ; preds = %entry
+ tail call void @llvm.ubsantrap(i8 2) #4, !nosanitize !5
+ unreachable, !nosanitize !5
+
+cont: ; preds = %entry
+ %2 = extractvalue { i32, i1 } %0, 0, !nosanitize !5
+ ret i32 %2
+}
+
+; Function Attrs: mustprogress nocallback nofree nosync nounwind speculatable willreturn memory(none)
+declare { i32, i1 } @llvm.sadd.with.overflow.i32(i32, i32) #1
+
+; Function Attrs: cold noreturn nounwind
+declare void @llvm.ubsantrap(i8 immarg) #2
+
+; Function Attrs: nounwind uwtable
+define dso_local range(i32 -2147483521, -2147483648) i32 @g(i32 noundef %x) local_unnamed_addr #0 {
+; CHECK-LABEL: g:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: addl $127, %edi
+; CHECK-NEXT: jo .LBB1_1
+; CHECK-NEXT: # %bb.2: # %cont
+; CHECK-NEXT: movl %edi, %eax
+; CHECK-NEXT: retq
+; CHECK-NEXT: .LBB1_1: # %trap
+; CHECK-NEXT: ud1l 2(%eax), %eax
+entry:
+ %0 = tail call { i32, i1 } @llvm.sadd.with.overflow.i32(i32 %x, i32 127), !nosanitize !5
+ %1 = extractvalue { i32, i1 } %0, 1, !nosanitize !5
+ br i1 %1, label %trap, label %cont, !nosanitize !5
+
+trap: ; preds = %entry
+ tail call void @llvm.ubsantrap(i8 2) #4, !nosanitize !5
+ unreachable, !nosanitize !5
+
+cont: ; preds = %entry
+ %2 = extractvalue { i32, i1 } %0, 0, !nosanitize !5
+ ret i32 %2
+}
+
+; Function Attrs: nounwind uwtable
+define dso_local range(i32 -2147483521, -2147483648) i32 @h(i32 noundef %x, i32 noundef %y) local_unnamed_addr #0 {
+; CHECK-LABEL: h:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: addl $127, %edi
+; CHECK-NEXT: jo .LBB2_3
+; CHECK-NEXT: # %bb.1: # %cont
+; CHECK-NEXT: addl $129, %esi
+; CHECK-NEXT: jo .LBB2_4
+; CHECK-NEXT: # %bb.2: # %cont2
+; CHECK-NEXT: cmpl %esi, %edi
+; CHECK-NEXT: cmovll %edi, %esi
+; CHECK-NEXT: movl %esi, %eax
+; CHECK-NEXT: retq
+; CHECK-NEXT: .LBB2_3: # %trap
+; CHECK-NEXT: ud1l 2(%eax), %eax
+; CHECK-NEXT: .LBB2_4: # %trap1
+; CHECK-NEXT: ud1l 4(%eax), %eax
+entry:
+ %0 = tail call { i32, i1 } @llvm.sadd.with.overflow.i32(i32 %x, i32 127), !nosanitize !5
+ %1 = extractvalue { i32, i1 } %0, 1, !nosanitize !5
+ br i1 %1, label %trap, label %cont, !nosanitize !5
+
+trap: ; preds = %entry
+ tail call void @llvm.ubsantrap(i8 2) #4, !nosanitize !5
+ unreachable, !nosanitize !5
+
+cont: ; preds = %entry
+ %2 = tail call { i32, i1 } @llvm.sadd.with.overflow.i32(i32 %y, i32 129), !nosanitize !5
+ %3 = extractvalue { i32, i1 } %2, 1, !nosanitize !5
+ br i1 %3, label %trap1, label %cont2, !nosanitize !5
+
+trap1: ; preds = %cont
+ tail call void @llvm.ubsantrap(i8 4) #4, !nosanitize !5
+ unreachable, !nosanitize !5
+
+cont2: ; preds = %cont
+ %4 = extractvalue { i32, i1 } %2, 0, !nosanitize !5
+ %5 = extractvalue { i32, i1 } %0, 0, !nosanitize !5
+ %cond = tail call i32 @llvm.smin.i32(i32 %5, i32 %4)
+ ret i32 %cond
+}
+
+; Function Attrs: nounwind uwtable
+define dso_local noundef i32 @m(i32 noundef %x, i32 noundef %y) local_unnamed_addr #0 {
+; CHECK-LABEL: m:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: addl $125, %edi
+; CHECK-NEXT: jo .LBB3_4
+; CHECK-NEXT: # %bb.1: # %f.exit
+; CHECK-NEXT: addl $127, %esi
+; CHECK-NEXT: jo .LBB3_4
+; CHECK-NEXT: # %bb.2: # %g.exit
+; CHECK-NEXT: addl %esi, %edi
+; CHECK-NEXT: jo .LBB3_4
+; CHECK-NEXT: # %bb.3: # %cont
+; CHECK-NEXT: movl %edi, %eax
+; CHECK-NEXT: retq
+; CHECK-NEXT: .LBB3_4: # %trap.i
+; CHECK-NEXT: ud1l 2(%eax), %eax
+entry:
+ %0 = tail call { i32, i1 } @llvm.sadd.with.overflow.i32(i32 %x, i32 125), !nosanitize !5
+ %1 = extractvalue { i32, i1 } %0, 1, !nosanitize !5
+ br i1 %1, label %trap.i, label %f.exit, !nosanitize !5
+
+trap.i: ; preds = %entry
+ tail call void @llvm.ubsantrap(i8 2) #4, !nosanitize !5
+ unreachable, !nosanitize !5
+
+f.exit: ; preds = %entry
+ %2 = tail call { i32, i1 } @llvm.sadd.with.overflow.i32(i32 %y, i32 127), !nosanitize !5
+ %3 = extractvalue { i32, i1 } %2, 1, !nosanitize !5
+ br i1 %3, label %trap.i2, label %g.exit, !nosanitize !5
+
+trap.i2: ; preds = %f.exit
+ tail call void @llvm.ubsantrap(i8 2) #4, !nosanitize !5
+ unreachable, !nosanitize !5
+
+g.exit: ; preds = %f.exit
+ %4 = extractvalue { i32, i1 } %0, 0, !nosanitize !5
+ %5 = extractvalue { i32, i1 } %2, 0, !nosanitize !5
+ %6 = tail call { i32, i1 } @llvm.sadd.with.overflow.i32(i32 %4, i32 %5), !nosanitize !5
+ %7 = extractvalue { i32, i1 } %6, 1, !nosanitize !5
+ br i1 %7, label %trap, label %cont, !nosanitize !5
+
+trap: ; preds = %g.exit
+ tail call void @llvm.ubsantrap(i8 2) #4, !nosanitize !5
+ unreachable, !nosanitize !5
+
+cont: ; preds = %g.exit
+ %8 = extractvalue { i32, i1 } %6, 0, !nosanitize !5
+ ret i32 %8
+}
+
+; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
+declare i32 @llvm.smin.i32(i32, i32) #3
+
+attributes #0 = { nounwind uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+attributes #1 = { mustprogress nocallback nofree nosync nounwind speculatable willreturn memory(none) }
+attributes #2 = { cold noreturn nounwind }
+attributes #3 = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }
+attributes #4 = { noreturn nounwind }
+
+!llvm.module.flags = !{!0, !1, !2, !3}
+!llvm.ident = !{!4}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{i32 8, !"PIC Level", i32 2}
+!2 = !{i32 7, !"PIE Level", i32 2}
+!3 = !{i32 7, !"uwtable", i32 2}
+!4 = !{!"clang version 20.0.0git (https://github.com/llvm/llvm-project.git fe3c23b439b9a2d00442d9bc6a4ca86f73066a3d)"}
+!5 = !{}
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vitalybuka
approved these changes
Nov 26, 2024
thurstond
added a commit
that referenced
this pull request
Nov 27, 2024
…117651) #65972 (continuation of https://reviews.llvm.org/D148654) had considered adding nomerge to ubsantrap, but did not proceed with that because of #53011. Instead, it added a counter (based on TrapBB->getParent()->size()) to each ubsantrap call. However, this counter is not guaranteed to be unique after inlining, as shown by #83470, which can result in ubsantraps being merged by the backend. #101549 has since fixed the nomerge limitation ("It sets nomerge flag for the node if the instruction has nomerge arrtibute."). This patch therefore takes advantage of nomerge instead of using the counter, guaranteeing that the ubsantraps are not merged. This patch is equivalent to #83470 but also adds nomerge and updates tests (#117649: ubsan-trap-merge.c; #117657: ubsan-trap-merge.ll, ubsan-trap-nomerge.ll; catch-undef-behavior.c).
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These testcases demonstrate that ubsan intrinsics are merged in the backend iff nomerge is missing from ubsantrap intrinsics.
This is based on the observation and testcase by Vitaly Buka in #83470.