[llvm] r190871 - SLPVectorizer: Don't vectorize phi nodes that use invoke values

[Quentin Colombet]

Hi Arnold,

I am curious, what is wrong with splitting critical edges?

Is it related to the potential cost it will incurved or is it just something we do not want to do?

Thanks,
-Quentin

On Sep 17, 2013, at 10:03 AM, Arnold Schwaighofer <aschwaighofer at apple.com> wrote:

> Author: arnolds
> Date: Tue Sep 17 12:03:29 2013
> New Revision: 190871
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=190871&view=rev
> Log:
> SLPVectorizer: Don't vectorize phi nodes that use invoke values
> 
> We can't insert an insertelement after an invoke. We would have to split a
> critical edge. So when we see a phi node that uses an invoke we just give up.
> 
> radar://14990770
> 
> Modified:
>    llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp
>    llvm/trunk/test/Transforms/SLPVectorizer/X86/ordering.ll
> 
> Modified: llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp?rev=190871&r1=190870&r2=190871&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp (original)
> +++ llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp Tue Sep 17 12:03:29 2013
> @@ -639,6 +639,18 @@ void BoUpSLP::buildTree_rec(ArrayRef<Val
>   switch (Opcode) {
>     case Instruction::PHI: {
>       PHINode *PH = dyn_cast<PHINode>(VL0);
> +
> +      // Check for terminator values (e.g. invoke).
> +      for (unsigned j = 0; j < VL.size(); ++j)
> +        for (unsigned i = 0, e = PH->getNumIncomingValues(); i < e; ++i) {
> +          TerminatorInst *Term = dyn_cast<TerminatorInst>(cast<PHINode>(VL[j])->getIncomingValue(i));
> +          if (Term) {
> +            DEBUG(dbgs() << "SLP: Need to swizzle PHINodes (TerminatorInst use).\n");
> +            newTreeEntry(VL, false);
> +            return;
> +          }
> +        }
> +
>       newTreeEntry(VL, true);
>       DEBUG(dbgs() << "SLP: added a vector of PHINodes.\n");
> 
> 
> Modified: llvm/trunk/test/Transforms/SLPVectorizer/X86/ordering.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SLPVectorizer/X86/ordering.ll?rev=190871&r1=190870&r2=190871&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/SLPVectorizer/X86/ordering.ll (original)
> +++ llvm/trunk/test/Transforms/SLPVectorizer/X86/ordering.ll Tue Sep 17 12:03:29 2013
> @@ -17,3 +17,65 @@ entry:
>   %cmp11 = fcmp olt double %add, 0.000000e+00
>   ret void
> }
> +
> +declare i8* @objc_msgSend(i8*, i8*, ...)
> +declare i32 @personality_v0(...)
> +
> +define void @invoketest() {
> +entry:
> +  br i1 undef, label %cond.true, label %cond.false
> +
> +cond.true:
> +  %call49 = invoke double bitcast (i8* (i8*, i8*, ...)* @objc_msgSend to double (i8*, i8*)*)(i8* undef, i8* undef) 
> +          to label %cond.true54 unwind label %lpad
> +
> +cond.false:
> +  %call51 = invoke double bitcast (i8* (i8*, i8*, ...)* @objc_msgSend to double (i8*, i8*)*)(i8* undef, i8* undef)
> +          to label %cond.false57 unwind label %lpad
> +
> +cond.true54:
> +  %call56 = invoke double bitcast (i8* (i8*, i8*, ...)* @objc_msgSend to double (i8*, i8*)*)(i8* undef, i8* undef) 
> +          to label %cond.end60 unwind label %lpad
> +
> +cond.false57:
> +  %call59 = invoke double bitcast (i8* (i8*, i8*, ...)* @objc_msgSend to double (i8*, i8*)*)(i8* undef, i8* undef)
> +          to label %cond.end60 unwind label %lpad
> +
> +; Make sure we don't vectorize these phis - they have invokes as inputs.
> +
> +; RUN: opt < %s -slp-vectorizer -S -mtriple=x86_64-apple-macosx10.8.0 -mcpu=corei7 | FileCheck %s
> +
> +; CHECK-LABEL: invoketest
> +
> +; CHECK-LABEL: cond.end60
> +; CHECK-NEXT-NOT: phi <2 x double>
> +; CHECK: insertelement
> +; CHECK-LABEL: if.then63
> +
> +cond.end60:
> +  %cond126 = phi double [ %call49, %cond.true54 ], [ %call51, %cond.false57 ]
> +  %cond61 = phi double [ %call56, %cond.true54 ], [ %call59, %cond.false57 ]
> +  br i1 undef, label %if.end98, label %if.then63
> +
> +if.then63:
> +  %conv69 = fptrunc double undef to float
> +  %conv70 = fpext float %conv69 to double
> +  %div71 = fdiv double %cond126, %conv70
> +  %conv78 = fptrunc double undef to float
> +  %conv79 = fpext float %conv78 to double
> +  %div80 = fdiv double %cond61, %conv79
> +  br label %if.end98
> +
> +lpad:
> +  %l = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @personality_v0 to i8*)
> +          cleanup
> +  resume { i8*, i32 } %l
> +
> +if.end98:
> +  %dimensionsResult.sroa.0.0 = phi double [ %div71, %if.then63 ], [ %cond126, %cond.end60 ]
> +  %dimensionsResult.sroa.6.0 = phi double [ %div80, %if.then63 ], [ %cond61, %cond.end60 ]
> +  br label %if.end99
> +
> +if.end99:
> +  ret void
> +}
> 
> 
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