[llvm-commits] [llvm] r125393 - in /llvm/trunk: lib/VMCore/ConstantFold.cpp test/Transforms/InstCombine/bitcast-vec-uniform.ll test/Transforms/InstCombine/fold-vector-select.ll

[Rotem, Nadav]

Hi Benjamin, 

Thank you for catching this.  

The patch below fixes the problem. If it looks good to you I will commit it. 

Thanks, 
Nadav

Details:
1. Added a test to reproduce the problem.
2. Added a check that the vector is of integer type. 


Index: ../llvm/test/Transforms/InstCombine/bitcast-vec-uniform.ll
===================================================================
--- ../llvm/test/Transforms/InstCombine/bitcast-vec-uniform.ll  (revision 125450)
+++ ../llvm/test/Transforms/InstCombine/bitcast-vec-uniform.ll  (working copy)
@@ -1,14 +1,30 @@
-; RUN: opt < %s -instcombine -S | not grep bitcast
+; RUN: opt < %s -instcombine -S | FileCheck %s

+; CHECK: @a
+; CHECK-NOT: bitcast
+; CHECK: ret
 define <4 x i32> @a(<1 x i64> %y) {
   %c = bitcast <2 x i64> <i64 0, i64 0> to <4 x i32>
   ret <4 x i32> %c
 }

+; CHECK: @b
+; CHECK-NOT: bitcast
+; CHECK: ret
+
 define <4 x i32> @b(<1 x i64> %y) {
   %c = bitcast <2 x i64> <i64 -1, i64 -1> to <4 x i32>
   ret <4 x i32> %c
 }

+; CHECK: @foo
+; CHECK: bitcast

+; from MultiSource/Benchmarks/Bullet
+define <2 x float> @foo() {
+  %cast = bitcast i64 -1 to <2 x float>
+  ret <2 x float> %cast
+}


Index: ../llvm/lib/VMCore/ConstantFold.cpp
===================================================================
--- ../llvm/lib/VMCore/ConstantFold.cpp (revision 125450)
+++ ../llvm/lib/VMCore/ConstantFold.cpp (working copy)
@@ -43,7 +43,8 @@
 static Constant *BitCastConstantVector(ConstantVector *CV,
                                        const VectorType *DstTy) {

-  if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy);
+  if (CV->isAllOnesValue() && DstTy->getElementType()->isIntegerTy())
+      return Constant::getAllOnesValue(DstTy);
   if (CV->isNullValue()) return Constant::getNullValue(DstTy);




-----Original Message-----
From: Benjamin Kramer [mailto:benny.kra at googlemail.com] 
Sent: Sunday, February 13, 2011 16:25
To: Rotem, Nadav
Cc: llvm-commits at cs.uiuc.edu
Subject: Re: [llvm-commits] [llvm] r125393 - in /llvm/trunk: lib/VMCore/ConstantFold.cpp test/Transforms/InstCombine/bitcast-vec-uniform.ll test/Transforms/InstCombine/fold-vector-select.ll


On 11.02.2011, at 20:37, Nadav Rotem wrote:

> Author: nadav
> Date: Fri Feb 11 13:37:55 2011
> New Revision: 125393
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=125393&view=rev
> Log:
> Fix 9173.
> 
> Add more folding patterns to constant expressions of vector selects and vector
> bitcasts.
> 
> 
> Added:
>    llvm/trunk/test/Transforms/InstCombine/bitcast-vec-uniform.ll   (with props)
>    llvm/trunk/test/Transforms/InstCombine/fold-vector-select.ll   (with props)
> Modified:
>    llvm/trunk/lib/VMCore/ConstantFold.cpp
> 
> Modified: llvm/trunk/lib/VMCore/ConstantFold.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/VMCore/ConstantFold.cpp?rev=125393&r1=125392&r2=125393&view=diff
> ==============================================================================
> --- llvm/trunk/lib/VMCore/ConstantFold.cpp (original)
> +++ llvm/trunk/lib/VMCore/ConstantFold.cpp Fri Feb 11 13:37:55 2011
> @@ -42,6 +42,10 @@
> /// input vector constant are all simple integer or FP values.
> static Constant *BitCastConstantVector(ConstantVector *CV,
>                                        const VectorType *DstTy) {
> +
> +  if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy);
> +  if (CV->isNullValue()) return Constant::getNullValue(DstTy);
> +

Hi Nadav,

it looks like this change caused a crash in MultiSource/Benchmarks/Bullet in the test-suite,
here's a reduced test case:

define <2 x float> @foo() {
  %cast = bitcast i64 -1 to <2 x float>
  ret <2 x float> %cast
}

the test hits an assertion with "opt -std-compile-opts" because Constant::getAllOnesValue
doesn't know how to handle floats.

- Benjamin
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