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

[David Majnemer via llvm-commits]

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]]
> > +}
>
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