From 76e7ba893fecd35422719acad5ab19af09bf4139 Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Sat, 18 Jul 2009 19:04:16 +0000
Subject: [PATCH] Back out 76300; apparently the preference is to canonicalize
 the other way (bitcast -> insert/extractelement).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76325 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/InstructionCombining.cpp | 22 ++++++----------------
 test/Transforms/InstCombine/vec-single-elt.ll  | 12 ------------
 2 files changed, 6 insertions(+), 28 deletions(-)
 delete mode 100644 test/Transforms/InstCombine/vec-single-elt.ll

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index e9e52944071..21b51e4cda1 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -12374,18 +12374,13 @@ Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) {
     if (op0)
       return ReplaceInstUsesWith(EI, op0);
   }
-
-  unsigned VectorWidth = 
-     cast<VectorType>(EI.getOperand(0)->getType())->getNumElements();
-
-  // Canonicalize extractelement from a vector of width 1 to a bitcast
-  if (VectorWidth == 1)
-    return new BitCastInst(EI.getOperand(0), EI.getType());
-
+  
   // If extracting a specified index from the vector, see if we can recursively
   // find a previously computed scalar that was inserted into the vector.
   if (ConstantInt *IdxC = dyn_cast<ConstantInt>(EI.getOperand(1))) {
     unsigned IndexVal = IdxC->getZExtValue();
+    unsigned VectorWidth = 
+      cast<VectorType>(EI.getOperand(0)->getType())->getNumElements();
       
     // If this is extracting an invalid index, turn this into undef, to avoid
     // crashing the code below.
@@ -12395,7 +12390,7 @@ Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) {
     // This instruction only demands the single element from the input vector.
     // If the input vector has a single use, simplify it based on this use
     // property.
-    if (EI.getOperand(0)->hasOneUse()) {
+    if (EI.getOperand(0)->hasOneUse() && VectorWidth != 1) {
       APInt UndefElts(VectorWidth, 0);
       APInt DemandedMask(VectorWidth, 1 << IndexVal);
       if (Value *V = SimplifyDemandedVectorElts(EI.getOperand(0),
@@ -12632,18 +12627,13 @@ Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
   // Inserting an undef or into an undefined place, remove this.
   if (isa<UndefValue>(ScalarOp) || isa<UndefValue>(IdxOp))
     ReplaceInstUsesWith(IE, VecOp);
-
-  unsigned NumVectorElts = IE.getType()->getNumElements();
-
-  // Canonicalize insertelement into vector of width 1 to a bitcast
-  if (NumVectorElts == 1)
-    return new BitCastInst(IE.getOperand(1), IE.getType());
-
+  
   // If the inserted element was extracted from some other vector, and if the 
   // indexes are constant, try to turn this into a shufflevector operation.
   if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)) {
     if (isa<ConstantInt>(EI->getOperand(1)) && isa<ConstantInt>(IdxOp) &&
         EI->getOperand(0)->getType() == IE.getType()) {
+      unsigned NumVectorElts = IE.getType()->getNumElements();
       unsigned ExtractedIdx =
         cast<ConstantInt>(EI->getOperand(1))->getZExtValue();
       unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue();
diff --git a/test/Transforms/InstCombine/vec-single-elt.ll b/test/Transforms/InstCombine/vec-single-elt.ll
deleted file mode 100644
index 45bca42c3e0..00000000000
--- a/test/Transforms/InstCombine/vec-single-elt.ll
+++ /dev/null
@@ -1,12 +0,0 @@
-; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep element
-; insert/extractelement should canonicalize to bitcast
-
-define i64 @a(<1 x i64> %x) {
-  %r = extractelement <1 x i64> %x, i32 0
-  ret i64 %r
-}
-
-define <1 x i64> @b(i64 %x) {
-  %r = insertelement <1 x i64> undef, i64 %x, i32 0
-  ret <1 x i64> %r
-}
-- 
2.11.0