[CodeGen] Don't emit lifetime intrinsics for some local variables
Summary:
Current generation of lifetime intrinsics does not handle cases like:
```
{
char x;
l1:
bar(&x, 1);
}
goto l1;
```
We will get code like this:
```
%x = alloca i8, align 1
call void @llvm.lifetime.start(i64 1, i8* nonnull %x)
br label %l1
l1:
%call = call i32 @bar(i8* nonnull %x, i32 1)
call void @llvm.lifetime.end(i64 1, i8* nonnull %x)
br label %l1
```
So the second time bar was called for x which is marked as dead.
Lifetime markers here are misleading so it's better to remove them at all.
This type of bypasses are rare, e.g. code detects just 8 functions building
clang (2329 targets).
PR28267
Reviewers: eugenis
Subscribers: beanz, mgorny, cfe-commits
Differential Revision: https://reviews.llvm.org/D24693
llvm-svn: 285176
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 123c040..7a6fd93 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -21,6 +21,7 @@
#include "CodeGenModule.h"
#include "CodeGenPGO.h"
#include "EHScopeStack.h"
+#include "VarBypassDetector.h"
#include "clang/AST/CharUnits.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExprObjC.h"
@@ -141,6 +142,10 @@
LoopInfoStack LoopStack;
CGBuilderTy Builder;
+ // Stores variables for which we can't generate correct lifetime markers
+ // because of jumps.
+ VarBypassDetector Bypasses;
+
/// \brief CGBuilder insert helper. This function is called after an
/// instruction is created using Builder.
void InsertHelper(llvm::Instruction *I, const llvm::Twine &Name,