clang++: BB's name affects generating IR (by NDEBUG)

[llvmbot]

Bugzilla Link	9450
Resolution	FIXED
Resolved on	Mar 30, 2011 06:33
Version	trunk
OS	All
Blocks	llvm/llvm-bugzilla-archive#9591
Attachments	Preprocessed llvm-ar.cpp and linux-generated IRs
Reporter	LLVM Bugzilla Contributor
CC	@efriedma-quic,@rjmccall

Extended Description

To build clang with both assertions.

In theory, stripped IRs might be identical regardless of Assertions.
attached ar-[ar].ll differs.
I met this issue on cygwin-1.7, though, I can reproduce on x86_64-linux.

Release/bin/clang++ -cc1 -triple=i686-pc-cygwin -O1 -emit-llvm -fcxx-exceptions llvm-ar.ii -o - | opt -strip -S -o ar-r.ll
Release+Asserts/bin/clang++ -cc1 -triple=i686-pc-cygwin -O1 -emit-llvm -fcxx-exceptions llvm-ar.ii -o - | opt -strip -S -o ar-a.ll

• with -O0, I can get same IRs.
• on +Asserts, I can get same IR if naming BB(s) is suppressed.

--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -1247,7 +1247,7 @@ public:
#ifdef NDEBUG
return llvm::BasicBlock::Create(getLLVMContext(), "", parent, before);
#else

• return llvm::BasicBlock::Create(getLLVMContext(), name, parent, before);

• return llvm::BasicBlock::Create(getLLVMContext(), "", parent, before);
  #endif
  }

Excuse me, I could not reduce my testcase.

ps. I know ToT llvm backend for Win32 does not support exceptions.

[rjmccall]

Things to check:
(1) if this duplicates at -O0
(2) if not, if it duplicates if you pass the unstripped -O0 output through opt -O1

If it duplicates with (2) then it's clearly an optimizer bug.

[llvmbot]

Reconfirmed on ToT x86_64-linux host.

$ for y in '' -O1 -O3; do
for x in Release Release+Asserts; do
/BUILD/llvm-static/$x/bin/clang++ -cc1
-triple=i686-pc-cygwin -O0 -emit-llvm
-fexceptions -fcxx-exceptions /tmp/llvm-ar.ii -o -
|/BUILD/llvm-static/$x/bin/opt $y
|~/BUILD/llvm-static/Release+Asserts/bin/opt -strip -S -o /tmp/ar-$x.ll;
done && cmp -s ar-Release+Asserts.ll ar-Release.ll || echo differs with $y;
done

$ for y in '' -O1 -O3; do
for x in Release Release+Asserts; do
/BUILD/llvm-static/$x/bin/clang++ -cc1 -triple=i686-pc-cygwin
$y -emit-llvm -fexceptions -fcxx-exceptions /tmp/llvm-ar.ii -o -
|/BUILD/llvm-static/Release+Asserts/bin/opt -strip -S -o /tmp/ar-$x.ll;
done && cmp -s ar-Release+Asserts.ll ar-Release.ll || echo differs with $y;
done
differs with -O1
differs with -O3

$

[efriedma-quic]

Relatively small test
Attached is dependent on memory addresses in SimplifyCFGOpt::SimplifyUnreachable. I'll try fixing that first.

[efriedma-quic]

Patch
Attached appears to fix the issue; it's a bit messy, though.

[rjmccall]

djg says this looks okay, so feel free to commit, Eli, or I will if you haven't in a day or so.

[llvmbot]

Created an attachment (id=6308) [details]
Patch

Attached appears to fix the issue; it's a bit messy, though.

Eli, thank you, it seems it has resolved most cases for me.
I have a few unresolved cases left regardless of Eli's patch.
I will investigate on. But I am afraid I would not do within a few days. :(

[efriedma-quic]

The given file is fixed with r127650. Please file a new bug if you find any other files with issues (just giving the preprocessed file is fine).

[llvmbot]

mentioned in issue llvm/llvm-bugzilla-archive#9591