From 275a6d66392c1752ba130aeeba11e257cd7a9c68 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Tue, 8 Sep 2009 18:48:01 +0000
Subject: [PATCH] remove an extremely dubious instcombine transformation of
 extractelement(load).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81239 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../Scalar/InstructionCombining.cpp           | 56 +++++--------------
 .../InstCombine/vec_extract_elt2.ll           | 23 --------
 2 files changed, 14 insertions(+), 65 deletions(-)
 delete mode 100644 test/Transforms/InstCombine/vec_extract_elt2.ll

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index fcbb4d351d5..47a02bd8427 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -12130,48 +12130,20 @@ Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) {
   }
   
   if (Instruction *I = dyn_cast<Instruction>(EI.getOperand(0))) {
-    if (I->hasOneUse()) {
-      // Push extractelement into predecessor operation if legal and
-      // profitable to do so
-      if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
-        bool isConstantElt = isa<ConstantInt>(EI.getOperand(1));
-        if (CheapToScalarize(BO, isConstantElt)) {
-          Value *newEI0 =
-            Builder->CreateExtractElement(BO->getOperand(0), EI.getOperand(1),
-                                          EI.getName()+".lhs");
-          Value *newEI1 =
-            Builder->CreateExtractElement(BO->getOperand(1), EI.getOperand(1),
-                                          EI.getName()+".rhs");
-          return BinaryOperator::Create(BO->getOpcode(), newEI0, newEI1);
-        }
-      } else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
-        // Instead of loading a vector, then doing an extract element out of it,
-        // just bitcast the pointer operand, do a gep, then load the result.
-        // This shrinks the vector load to a scalar load.
-        if (EI.getVectorOperandType()->getNumElements() != 1) {
-          unsigned AS = LI->getPointerAddressSpace();
-          Value *Ptr = Builder->CreateBitCast(I->getOperand(0),
-                                              PointerType::get(EI.getType(), AS),
-                                              I->getOperand(0)->getName());
-          Value *GEP =
-            Builder->CreateInBoundsGEP(Ptr, EI.getOperand(1),
-                                       I->getName()+".gep");
-          
-          LoadInst *Load = Builder->CreateLoad(GEP, "tmp");
-
-          // Make sure the Load goes before the load instruction in the source,
-          // not wherever the extract happens to be.
-          if (Instruction *P = dyn_cast<Instruction>(Ptr))
-            P->moveBefore(I);
-          if (Instruction *G = dyn_cast<Instruction>(GEP))
-            G->moveBefore(I);
-          Load->moveBefore(I);
-          
-          return ReplaceInstUsesWith(EI, Load);
-        }
-      }
-    }
-    if (InsertElementInst *IE = dyn_cast<InsertElementInst>(I)) {
+    // Push extractelement into predecessor operation if legal and
+    // profitable to do so
+    if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
+      if (I->hasOneUse() &&
+          CheapToScalarize(BO, isa<ConstantInt>(EI.getOperand(1)))) {
+        Value *newEI0 =
+          Builder->CreateExtractElement(BO->getOperand(0), EI.getOperand(1),
+                                        EI.getName()+".lhs");
+        Value *newEI1 =
+          Builder->CreateExtractElement(BO->getOperand(1), EI.getOperand(1),
+                                        EI.getName()+".rhs");
+        return BinaryOperator::Create(BO->getOpcode(), newEI0, newEI1);
+      }
+    } else if (InsertElementInst *IE = dyn_cast<InsertElementInst>(I)) {
       // Extracting the inserted element?
       if (IE->getOperand(2) == EI.getOperand(1))
         return ReplaceInstUsesWith(EI, IE->getOperand(1));
diff --git a/test/Transforms/InstCombine/vec_extract_elt2.ll b/test/Transforms/InstCombine/vec_extract_elt2.ll
deleted file mode 100644
index 216d7ef05ba..00000000000
--- a/test/Transforms/InstCombine/vec_extract_elt2.ll
+++ /dev/null
@@ -1,23 +0,0 @@
-; RUN: opt %s -instcombine | llvm-dis | FileCheck %s
-
-; The load replacing the extract element must occur before the call
-; that may modify local array a.
-
-declare void @mod_a_func(<4 x float>* %a);
-
-; CHECK: load float* %arraydecay1, align 16
-; CHECK: call void @mod_a_func
-
-define void @cl_jpegenc_k2(<4 x float> addrspace(1)* %src, float addrspace(1)* %dst) {
-  %a = alloca [2 x <4 x float>], align 16
-  %arraydecay = getelementptr [2 x <4 x float>]* %a, i32 0, i32 0
-  %arrayidx31 = getelementptr <4 x float> addrspace(1)* %src, i32 0
-  %tmp32 = load <4 x float> addrspace(1)* %arrayidx31
-  store <4 x float> %tmp32, <4 x float>* %arraydecay, align 16
-  %tmp86 = load <4 x float>* %arraydecay, align 16
-  call void @mod_a_func(<4 x float>* %arraydecay)
-  %arrayidx132 = getelementptr float addrspace(1)* %dst, i32 0
-  %tmp236 = extractelement <4 x float> %tmp86, i32 0
-  store float %tmp236, float addrspace(1)* %arrayidx132
-  ret void
-}
\ No newline at end of file
-- 
2.34.1