[clang] Do not merge traps in functions annotated optnone

This aligns the behaviour with that of disabling optimisations for the
translation unit entirely. Not merging the traps allows us to keep
separate debug information for each, improving the debugging experience
when finding the cause for a ubsan trap.

Differential Revision: https://reviews.llvm.org/D137714

diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index d2d2ace..5021fc7 100644 (file)
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -3550,7 +3550,8 @@ void CodeGenFunction::EmitTrapCheck(llvm::Value *Checked,
     TrapBBs.resize(CheckHandlerID + 1);
   llvm::BasicBlock *&TrapBB = TrapBBs[CheckHandlerID];
 
-  if (!CGM.getCodeGenOpts().OptimizationLevel || !TrapBB) {
+  if (!CGM.getCodeGenOpts().OptimizationLevel || !TrapBB ||
+      (CurCodeDecl && CurCodeDecl->hasAttr<OptimizeNoneAttr>())) {
     TrapBB = createBasicBlock("trap");
     Builder.CreateCondBr(Checked, Cont, TrapBB);
     EmitBlock(TrapBB);

diff --git a/clang/test/CodeGen/ubsan-trap-debugloc.c b/clang/test/CodeGen/ubsan-trap-debugloc.c
index d73cf73..4cad708 100644 (file)
--- a/clang/test/CodeGen/ubsan-trap-debugloc.c
+++ b/clang/test/CodeGen/ubsan-trap-debugloc.c
@@ -2,9 +2,23 @@
 
 
 void foo(volatile int a) {
+  // CHECK-LABEL: @foo
   // CHECK: call void @llvm.ubsantrap(i8 0){{.*}} !dbg [[LOC:![0-9]+]]
   a = a + 1;
   a = a + 1;
 }
 
+void bar(volatile int a) __attribute__((optnone)) {
+  // CHECK-LABEL: @bar
+  // CHECK: call void @llvm.ubsantrap(i8 0){{.*}} !dbg [[LOC2:![0-9]+]]
+  // CHECK: call void @llvm.ubsantrap(i8 0){{.*}} !dbg [[LOC3:![0-9]+]]
+  a = a + 1;
+  a = a + 1;
+}
+
+// With optimisations enabled the traps are merged and need to share a debug location
 // CHECK: [[LOC]] = !DILocation(line: 0
+
+// With optimisations disabled the traps are not merged and retain accurate debug locations
+// CHECK: [[LOC2]] = !DILocation(line: 15, column: 9
+// CHECK: [[LOC3]] = !DILocation(line: 16, column: 9