[CodeGen] Suppress emission of lifetime markers if a label has been seen
in the current lexical scope.
clang currently emits the lifetime.start marker of a variable when the
variable comes into scope even though a variable's lifetime starts at
the entry of the block with which it is associated, according to the C
standard. This normally doesn't cause any problems, but in the rare case
where a goto jumps backwards past the variable declaration to an earlier
point in the block (see the test case added to lifetime2.c), it can
cause mis-compilation.
To prevent such mis-compiles, this commit conservatively disables
emitting lifetime variables when a label has been seen in the current
block.
This problem was discussed on cfe-dev here:
http://lists.llvm.org/pipermail/cfe-dev/2016-July/050066.html
rdar://problem/30153946
Differential Revision: https://reviews.llvm.org/D27680
llvm-svn: 293106
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 82ab5c3..8d7fd3f 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -212,6 +212,13 @@
/// value. This is invalid iff the function has no return value.
Address ReturnValue;
+ /// Return true if a label was seen in the current scope.
+ bool hasLabelBeenSeenInCurrentScope() const {
+ if (CurLexicalScope)
+ return CurLexicalScope->hasLabels();
+ return !LabelMap.empty();
+ }
+
/// AllocaInsertPoint - This is an instruction in the entry block before which
/// we prefer to insert allocas.
llvm::AssertingVH<llvm::Instruction> AllocaInsertPt;
@@ -620,6 +627,10 @@
rescopeLabels();
}
+ bool hasLabels() const {
+ return !Labels.empty();
+ }
+
void rescopeLabels();
};