From cf1e58c00294ee005b4b5269a75de4c80096ba50 Mon Sep 17 00:00:00 2001
From: Mehdi Amini <mehdi.amini@apple.com>
Date: Wed, 9 Dec 2015 16:31:39 +0000
Subject: [PATCH] Revert "[InstCombine] fold bitcasts around an extractelement"

This reverts commit r255124.

Broke http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-ubuntu-fast/builds/4193/steps/test/logs/stdio

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@255126 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../InstCombine/InstCombineCasts.cpp          | 37 -------------------
 test/Transforms/InstCombine/bitcast.ll        | 13 ++++---
 2 files changed, 8 insertions(+), 42 deletions(-)

diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index 23bf40124b5..4afe1bb243f 100644
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -1715,40 +1715,6 @@ static Value *optimizeIntegerToVectorInsertions(BitCastInst &CI,
   return Result;
 }
 
-/// Given a bitcasted vector fed into an extract element instruction and then
-/// bitcasted again, eliminate at least one bitcast by changing the vector type
-/// of the extractelement instruction.
-/// Example:
-///   bitcast (extractelement (bitcast <2 x float> %X to <2 x i32>), 1) to float
-///    --->
-///   extractelement <2 x float> %X, i32 1
-static Instruction *foldBitCastExtElt(BitCastInst &BitCast, InstCombiner &IC,
-                                      const DataLayout &DL) {
-  // TODO: Create and use a pattern matcher for ExtractElementInst.
-  auto *ExtElt = dyn_cast<ExtractElementInst>(BitCast.getOperand(0));
-  if (!ExtElt || !ExtElt->hasOneUse())
-    return nullptr;
-
-  Value *InnerBitCast = nullptr;
-  if (!match(ExtElt->getOperand(0), m_BitCast(m_Value(InnerBitCast))))
-    return nullptr;
-
-  VectorType *VecType = cast<VectorType>(InnerBitCast->getType());
-  Type *DestType = BitCast.getType();
-
-  // If the element type of the vector doesn't match the result type,
-  // bitcast it to a vector type that we can extract from.
-  if (VecType->getElementType() != DestType) {
-    unsigned VecWidth = VecType->getPrimitiveSizeInBits();
-    unsigned DestWidth = DestType->getPrimitiveSizeInBits();
-    unsigned NumElts = VecWidth / DestWidth;
-    VecType = VectorType::get(DestType, NumElts);
-    InnerBitCast = IC.Builder->CreateBitCast(InnerBitCast, VecType, "bc");
-  }
-
-  return ExtractElementInst::Create(InnerBitCast, ExtElt->getOperand(1));
-}
-
 static Instruction *foldVecTruncToExtElt(Value *VecInput, Type *DestTy,
                                          unsigned ShiftAmt, InstCombiner &IC,
                                          const DataLayout &DL) {
@@ -1920,9 +1886,6 @@ Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
     }
   }
 
-  if (Instruction *I = foldBitCastExtElt(CI, *this, DL))
-    return I;
-
   if (SrcTy->isPointerTy())
     return commonPointerCastTransforms(CI);
   return commonCastTransforms(CI);
diff --git a/test/Transforms/InstCombine/bitcast.ll b/test/Transforms/InstCombine/bitcast.ll
index 132147f6532..2a8194e5303 100644
--- a/test/Transforms/InstCombine/bitcast.ll
+++ b/test/Transforms/InstCombine/bitcast.ll
@@ -64,7 +64,7 @@ define float @test3(<2 x float> %A, <2 x i64> %B) {
 ; CHECK-NEXT:  ret float %add
 }
 
-; Both bitcasts are unnecessary; change the extractelement.
+; TODO: Both bitcasts are unnecessary; change the extractelement.
 
 define float @bitcast_extelt1(<2 x float> %A) {
   %bc1 = bitcast <2 x float> %A to <2 x i32>
@@ -73,11 +73,13 @@ define float @bitcast_extelt1(<2 x float> %A) {
   ret float %bc2
 
 ; CHECK-LABEL: @bitcast_extelt1(
-; CHECK-NEXT:  %bc2 = extractelement <2 x float> %A, i32 0
+; CHECK-NEXT:  %bc1 = bitcast <2 x float> %A to <2 x i32>
+; CHECK-NEXT:  %ext = extractelement <2 x i32> %bc1, i32 0
+; CHECK-NEXT:  %bc2 = bitcast i32 %ext to float
 ; CHECK-NEXT:  ret float %bc2
 }
 
-; Second bitcast can be folded into the first.
+; TODO: Second bitcast can be folded into the first.
 
 define i64 @bitcast_extelt2(<4 x float> %A) {
   %bc1 = bitcast <4 x float> %A to <2 x double>
@@ -86,8 +88,9 @@ define i64 @bitcast_extelt2(<4 x float> %A) {
   ret i64 %bc2
 
 ; CHECK-LABEL: @bitcast_extelt2(
-; CHECK-NEXT:  %bc = bitcast <4 x float> %A to <2 x i64>
-; CHECK-NEXT:  %bc2 = extractelement <2 x i64> %bc, i32 1
+; CHECK-NEXT:  %bc1 = bitcast <4 x float> %A to <2 x double>
+; CHECK-NEXT:  %ext = extractelement <2 x double> %bc1, i32 1
+; CHECK-NEXT:  %bc2 = bitcast double %ext to i64
 ; CHECK-NEXT:  ret i64 %bc2
 }
 
-- 
2.34.1