[llvm] r245365 - [InstSimplify] Don't assume getAggregateElement will succeed

[Hans Wennborg via llvm-commits]

Merged together with r245369 in r245572.

Cheers,
Hans

On Wed, Aug 19, 2015 at 7:07 PM, David Majnemer
<david.majnemer at gmail.com> wrote:
> Yes, I think we should.
>
> On Wed, Aug 19, 2015 at 1:56 PM, Hans Wennborg <hans at chromium.org> wrote:
>>
>> Is this a fix we should merge to 3.7?
>>
>> On Tue, Aug 18, 2015 at 3:07 PM, David Majnemer via llvm-commits
>> <llvm-commits at lists.llvm.org> wrote:
>> > Author: majnemer
>> > Date: Tue Aug 18 17:07:25 2015
>> > New Revision: 245365
>> >
>> > URL: http://llvm.org/viewvc/llvm-project?rev=245365&view=rev
>> > Log:
>> > [InstSimplify] Don't assume getAggregateElement will succeed
>> >
>> > It isn't always possible to get a value from getAggregateElement.
>> > This fixes PR24488.
>> >
>> > Modified:
>> >     llvm/trunk/lib/Analysis/InstructionSimplify.cpp
>> >     llvm/trunk/lib/Analysis/VectorUtils.cpp
>> >
>> > llvm/trunk/test/Transforms/InstSimplify/2011-09-05-InsertExtractValue.ll
>> >
>> > Modified: llvm/trunk/lib/Analysis/InstructionSimplify.cpp
>> > URL:
>> > http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InstructionSimplify.cpp?rev=245365&r1=245364&r2=245365&view=diff
>> >
>> > ==============================================================================
>> > --- llvm/trunk/lib/Analysis/InstructionSimplify.cpp (original)
>> > +++ llvm/trunk/lib/Analysis/InstructionSimplify.cpp Tue Aug 18 17:07:25
>> > 2015
>> > @@ -3578,11 +3578,6 @@ static Value *SimplifyExtractElementInst
>> >      unsigned IndexVal = IdxC->getZExtValue();
>> >      unsigned VectorWidth = Vec->getType()->getVectorNumElements();
>> >
>> > -    // If this is extracting an invalid index, turn this into undef, to
>> > avoid
>> > -    // crashing the code below.
>> > -    if (IndexVal >= VectorWidth)
>> > -      return UndefValue::get(Vec->getType()->getVectorElementType());
>> > -
>> >      if (Value *Elt = findScalarElement(Vec, IndexVal))
>> >        return Elt;
>> >    }
>> >
>> > Modified: llvm/trunk/lib/Analysis/VectorUtils.cpp
>> > URL:
>> > http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/VectorUtils.cpp?rev=245365&r1=245364&r2=245365&view=diff
>> >
>> > ==============================================================================
>> > --- llvm/trunk/lib/Analysis/VectorUtils.cpp (original)
>> > +++ llvm/trunk/lib/Analysis/VectorUtils.cpp Tue Aug 18 17:07:25 2015
>> > @@ -398,10 +398,10 @@ Value *llvm::findScalarElement(Value *V,
>> >
>> >    // Extract a value from a vector add operation with a constant zero.
>> >    Value *Val = nullptr; Constant *Con = nullptr;
>> > -  if (match(V, m_Add(m_Value(Val), m_Constant(Con)))) {
>> > -    if (Con->getAggregateElement(EltNo)->isNullValue())
>> > -      return findScalarElement(Val, EltNo);
>> > -  }
>> > +  if (match(V, m_Add(m_Value(Val), m_Constant(Con))))
>> > +    if (Constant *Elt = Con->getAggregateElement(EltNo))
>> > +      if (Elt->isNullValue())
>> > +        return findScalarElement(Val, EltNo);
>> >
>> >    // Otherwise, we don't know.
>> >    return nullptr;
>> >
>> > Modified:
>> > llvm/trunk/test/Transforms/InstSimplify/2011-09-05-InsertExtractValue.ll
>> > URL:
>> > http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/2011-09-05-InsertExtractValue.ll?rev=245365&r1=245364&r2=245365&view=diff
>> >
>> > ==============================================================================
>> > ---
>> > llvm/trunk/test/Transforms/InstSimplify/2011-09-05-InsertExtractValue.ll
>> > (original)
>> > +++
>> > llvm/trunk/test/Transforms/InstSimplify/2011-09-05-InsertExtractValue.ll Tue
>> > Aug 18 17:07:25 2015
>> > @@ -36,3 +36,13 @@ define i32 @test3(i32 %a, float %b) {
>> >  ; CHECK-LABEL: @test3(
>> >  ; CHECK: ret i32 %a
>> >  }
>> > +
>> > +define i8 @test4(<8 x i8> %V) {
>> > +  %add     = add <8 x i8> %V, bitcast (double 0x319BEB8FD172E36 to <8 x
>> > i8>)
>> > +  %extract = extractelement <8 x i8> %add, i32 6
>> > +  ret i8 %extract
>> > +; CHECK-LABEL: @test4(
>> > +; CHECK: %[[add:.*]] = add <8 x i8> %V, bitcast (<1 x double> <double
>> > 0x319BEB8FD172E36> to <8 x i8>)
>> > +; CHECK-NEXT: %[[extract:.*]] = extractelement <8 x i8> %[[add]], i32 6
>> > +; CHECK-NEXT: ret i8 %[[extract]]
>> > +}
>
>