Modify array-bounds sanitizer to improve debuggability

Author: oskarwirga

clang/lib/CodeGen/CGExpr.cpp

@@ -51,6 +51,12 @@
 using namespace clang;
 using namespace CodeGen;
 
+// Experiment to make sanitizers easier to debug
+static llvm::cl::opt<bool> ClSanitizeDebugDeoptimization(
+    "ubsan-unique-traps", llvm::cl::Optional,
+    llvm::cl::desc("Deoptimize traps for UBSAN so there is 1 trap per check"),
+    llvm::cl::init(false));
+
 //===--------------------------------------------------------------------===//
 //                        Miscellaneous Helper Methods
 //===--------------------------------------------------------------------===//
@@ -3553,17 +3559,28 @@ void CodeGenFunction::EmitTrapCheck(llvm::Value *Checked,
   // check-type per function to save on code size.
   if (TrapBBs.size() <= CheckHandlerID)
     TrapBBs.resize(CheckHandlerID + 1);
+
   llvm::BasicBlock *&TrapBB = TrapBBs[CheckHandlerID];
 
-  if (!CGM.getCodeGenOpts().OptimizationLevel || !TrapBB ||
-      (CurCodeDecl && CurCodeDecl->hasAttr<OptimizeNoneAttr>())) {
+  if (!ClSanitizeDebugDeoptimization &&
+      CGM.getCodeGenOpts().OptimizationLevel && TrapBB &&
+      (!CurCodeDecl || !CurCodeDecl->hasAttr<OptimizeNoneAttr>())) {
+    auto Call = TrapBB->begin();
+    assert(isa<llvm::CallInst>(Call) && "Expected call in trap BB");
+
+    Call->applyMergedLocation(Call->getDebugLoc(),
+                              Builder.getCurrentDebugLocation());
+    Builder.CreateCondBr(Checked, Cont, TrapBB);
+  } else {
     TrapBB = createBasicBlock("trap");
     Builder.CreateCondBr(Checked, Cont, TrapBB);
     EmitBlock(TrapBB);
 
-    llvm::CallInst *TrapCall =
-        Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::ubsantrap),
-                           llvm::ConstantInt::get(CGM.Int8Ty, CheckHandlerID));
+    llvm::CallInst *TrapCall = Builder.CreateCall(
+        CGM.getIntrinsic(llvm::Intrinsic::ubsantrap),
+        llvm::ConstantInt::get(CGM.Int8Ty, ClSanitizeDebugDeoptimization
+                                               ? TrapBB->getParent()->size()
+                                               : CheckHandlerID));
 
     if (!CGM.getCodeGenOpts().TrapFuncName.empty()) {
       auto A = llvm::Attribute::get(getLLVMContext(), "trap-func-name",
@@ -3573,13 +3590,6 @@ void CodeGenFunction::EmitTrapCheck(llvm::Value *Checked,
     TrapCall->setDoesNotReturn();
     TrapCall->setDoesNotThrow();
     Builder.CreateUnreachable();
-  } else {
-    auto Call = TrapBB->begin();
-    assert(isa<llvm::CallInst>(Call) && "Expected call in trap BB");
-
-    Call->applyMergedLocation(Call->getDebugLoc(),
-                              Builder.getCurrentDebugLocation());
-    Builder.CreateCondBr(Checked, Cont, TrapBB);
   }
 
   EmitBlock(Cont);

clang/test/CodeGen/bounds-checking.c

@@ -1,5 +1,6 @@
 // RUN: %clang_cc1 -fsanitize=local-bounds -emit-llvm -triple x86_64-apple-darwin10 %s -o - | FileCheck %s
 // RUN: %clang_cc1 -fsanitize=array-bounds -O -fsanitize-trap=array-bounds -emit-llvm -triple x86_64-apple-darwin10 -DNO_DYNAMIC %s -o - | FileCheck %s
+// RUN: %clang_cc1 -fsanitize=array-bounds -fsanitize-trap=array-bounds -O3 -mllvm -ubsan-unique-traps -emit-llvm -triple x86_64-apple-darwin10 %s -o - | FileCheck %s --check-prefixes=NOOPTARRAY
 //
 // REQUIRES: x86-registered-target
 
@@ -66,3 +67,15 @@ int f7(union U *u, int i) {
   // CHECK-NOT: @llvm.ubsantrap
   return u->c[i];
 }
+
+
+char B[10];
+char B2[10];
+// CHECK-LABEL: @f8
+void f8(int i, int k) {
+  // NOOPTARRAY: call void @llvm.ubsantrap(i8 2)
+  B[i] = '\0';
+
+  // NOOPTARRAY: call void @llvm.ubsantrap(i8 4)
+  B2[k] = '\0';
+}