clang hang

[regehr]

Bugzilla Link	9013
Resolution	FIXED
Resolved on	Jan 20, 2011 23:30
Version	trunk
OS	Linux
CC	@tkremenek

Extended Description

This bug appeared during the last week or so.

'clang -O2' loops apparently forever when trying to compile the code below.

This is r123879 on x86 Linux.

static int foo (int si1, int si2)
{
return si1 - si2;
}

void bar (void)
{
unsigned char l_197;
for (;; l_197 = foo (l_197, 1))
;
}

[tkremenek]

Hangs for me as well on Mac OS X.

[tkremenek]

The debugger shows we are in InstCombine:

#​0 0x0000000100ca68a3 in llvm::value_use_iteratorllvm::User::operator== (this=0x7fff5fbfad58, x=@0x7fff5fbfad50) at /Volumes/Data/code/llvm/include/llvm/Use.h:173
#​1 0x000000010173e9b9 in llvm::value_use_iteratorllvm::User::operator!= (this=0x7fff5fbfad58, x=@0x7fff5fbfad50) at /Volumes/Data/code/llvm/include/llvm/Use.h:176
#​2 0x00000001016a28b2 in llvm::InstCombineWorklist::AddUsersToWorkList (this=0x106064230, I=@0x1058553b0) at /Volumes/Data/code/llvm/lib/Transforms/InstCombine/InstCombineWorklist.h:87
#​3 0x00000001016a0ed6 in llvm::InstCombiner::ReplaceInstUsesWith (this=0x106064200, I=@0x1058553b0, V=0x10584c370) at /Volumes/Data/code/llvm/lib/Transforms/InstCombine/InstCombine.h:242
#​4 0x000000010169a465 in llvm::InstCombiner::FoldOpIntoPhi (this=0x106064200, I=@0x1058553b0) at /Volumes/Data/code/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp:642
#​5 0x00000001016a766a in llvm::InstCombiner::visitAdd (this=0x106064200, I=@0x1058553b0) at /Volumes/Data/code/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp:118
#​6 0x00000001016a2276 in llvm::InstVisitor<llvm::InstCombiner, llvm::Instruction*>::visit (this=0x106064200, I=@0x1058553b0) at /Volumes/Data/code/llvm/include/llvm/Instruction.def:108
#​7 0x000000010169f23b in llvm::InstCombiner::DoOneIteration (this=0x106064200, F=@0x105818ce0, Iteration=13154) at /Volumes/Data/code/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp:1548
#​8 0x00000001016a02a1 in llvm::InstCombiner::runOnFunction (this=0x106064200, F=@0x105818ce0) at /Volumes/Data/code/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp:1616
#​9 0x00000001019a46f5 in llvm::FPPassManager::runOnFunction (this=0x105823f70, F=@0x105818ce0) at /Volumes/Data/code/llvm/lib/VMCore/PassManager.cpp:1452

[tkremenek]

cloned to rdar://problem/8892503

[lattner]

Looks like a regression due to my r123520 patch, investigating.

[lattner]

Fixed in r123968, thanks John!