[llvm-commits] [llvm] r158951 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineCalls.cpp test/Transforms/InstCombine/invoke.ll

[Duncan Sands]

Hi Nuno,

>>> instcombine: disable optimization of 'invoke null/undef'. I'll move this
>>> functionality to SimplifyCFG (since we cannot make changes to the CFG here).
>>> Fixes the crashes with the attached test case
>>
>> can you just set "nounwind" on the invoke? (Not sure if that is possible -
>> maybe for an invoke it can only be done on the callee?). Then some other
>> pass will magically take care of it.
>
> Actually that code was doing a bit more than removing the invoke. It was
> inserting an undefined operation before 'invoke null/undef' so that the simplify
> CFG pass could then replace the invoke with unreachable. My idea was to move
> this logic (invoke null -> unreachable) into simplify CFG. Sounds reasonable?

yes, that sounds reasonable.  You can still cheat (mark it nounwind in
instcombine, and implement "call null" -> unreachable, which maybe is done
already) but it's maybe clearer and no harder to do it directly.

Ciao, Duncan.

>
> Nuno
>
>
>> Ciao, Duncan.
>>
>>>
>>> Added:
>>> llvm/trunk/test/Transforms/InstCombine/invoke.ll
>>> Modified:
>>> llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
>>>
>>> Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp?rev=158951&r1=158950&r2=158951&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp (original)
>>> +++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp Thu Jun 21
>>> 18:52:14 2012
>>> @@ -917,24 +917,24 @@
>>> }
>>>
>>> if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
>>> - // This instruction is not reachable, just remove it. We insert a store to
>>> - // undef so that we know that this code is not reachable, despite the fact
>>> - // that we can't modify the CFG here.
>>> - new StoreInst(ConstantInt::getTrue(Callee->getContext()),
>>> - UndefValue::get(Type::getInt1PtrTy(Callee->getContext())),
>>> - CS.getInstruction());
>>> -
>>> // If CS does not return void then replaceAllUsesWith undef.
>>> // This allows ValueHandlers and custom metadata to adjust itself.
>>> if (!CS.getInstruction()->getType()->isVoidTy())
>>> ReplaceInstUsesWith(*CS.getInstruction(),
>>> UndefValue::get(CS.getInstruction()->getType()));
>>>
>>> - if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
>>> - // Don't break the CFG, insert a dummy cond branch.
>>> - BranchInst::Create(II->getNormalDest(), II->getUnwindDest(),
>>> - ConstantInt::getTrue(Callee->getContext()), II);
>>> + if (isa<InvokeInst>(CS.getInstruction())) {
>>> + // Can't remove an invoke because we cannot change the CFG.
>>> + return 0;
>>> }
>>> +
>>> + // This instruction is not reachable, just remove it. We insert a store to
>>> + // undef so that we know that this code is not reachable, despite the fact
>>> + // that we can't modify the CFG here.
>>> + new StoreInst(ConstantInt::getTrue(Callee->getContext()),
>>> + UndefValue::get(Type::getInt1PtrTy(Callee->getContext())),
>>> + CS.getInstruction());
>>> +
>>> return EraseInstFromFunction(*CS.getInstruction());
>>> }
>>>
>>>
>>> Added: llvm/trunk/test/Transforms/InstCombine/invoke.ll
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/invoke.ll?rev=158951&view=auto
>>>
>>> ==============================================================================
>>> --- llvm/trunk/test/Transforms/InstCombine/invoke.ll (added)
>>> +++ llvm/trunk/test/Transforms/InstCombine/invoke.ll Thu Jun 21 18:52:14 2012
>>> @@ -0,0 +1,47 @@
>>> +; RUN: opt< %s -instcombine -S | FileCheck %s
>>> +target datalayout =
>>> "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
>>>
>>> +
>>> +declare i32 @__gxx_personality_v0(...)
>>> +declare void @__cxa_call_unexpected(i8*)
>>> +declare i64 @llvm.objectsize.i64(i8*, i1) nounwind readonly
>>> +
>>> +
>>> +; CHECK: @f1
>>> +define i64 @f1() nounwind uwtable ssp {
>>> +entry:
>>> +; CHECK: nvoke noalias i8* undef()
>>> + %call = invoke noalias i8* undef()
>>> + to label %invoke.cont unwind label %lpad
>>> +
>>> +invoke.cont:
>>> +; CHECK: ret i64 0
>>> + %0 = tail call i64 @llvm.objectsize.i64(i8* %call, i1 false)
>>> + ret i64 %0
>>> +
>>> +lpad:
>>> + %1 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)*
>>> @__gxx_personality_v0 to i8*)
>>> + filter [0 x i8*] zeroinitializer
>>> + %2 = extractvalue { i8*, i32 } %1, 0
>>> + tail call void @__cxa_call_unexpected(i8* %2) noreturn nounwind
>>> + unreachable
>>> +}
>>> +
>>> +; CHECK: @f2
>>> +define i64 @f2() nounwind uwtable ssp {
>>> +entry:
>>> +; CHECK: nvoke noalias i8* null()
>>> + %call = invoke noalias i8* null()
>>> + to label %invoke.cont unwind label %lpad
>>> +
>>> +invoke.cont:
>>> +; CHECK: ret i64 0
>>> + %0 = tail call i64 @llvm.objectsize.i64(i8* %call, i1 false)
>>> + ret i64 %0
>>> +
>>> +lpad:
>>> + %1 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)*
>>> @__gxx_personality_v0 to i8*)
>>> + filter [0 x i8*] zeroinitializer
>>> + %2 = extractvalue { i8*, i32 } %1, 0
>>> + tail call void @__cxa_call_unexpected(i8* %2) noreturn nounwind
>>> + unreachable
>>> +}
>>>