From 38b3dcc4651606c683d864f11cd27852810f3936 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Mon, 1 Dec 2008 03:42:51 +0000
Subject: [PATCH] Change instcombine to use FoldPHIArgGEPIntoPHI to fold two
 operand PHIs instead of using FoldPHIArgBinOpIntoPHI.  In addition to being
 more obvious, this also fixes a problem where instcombine wouldn't merge two
 phis that had different variable indices.  This prevented instcombine from
 factoring big chunks of code in 403.gcc.  For example:

 insn_cuid.exit:
-       %tmp336 = load i32** @uid_cuid, align 4
-       %tmp337 = getelementptr %struct.rtx_def* %insn_addr.0.ph.i, i32 0, i32 3
-       %tmp338 = bitcast [1 x %struct.rtunion]* %tmp337 to i32*
-       %tmp339 = load i32* %tmp338, align 4
-       %tmp340 = getelementptr i32* %tmp336, i32 %tmp339
        br label %bb62

 bb61:
-       %tmp341 = load i32** @uid_cuid, align 4
-       %tmp342 = getelementptr %struct.rtx_def* %insn, i32 0, i32 3
-       %tmp343 = bitcast [1 x %struct.rtunion]* %tmp342 to i32*
-       %tmp344 = load i32* %tmp343, align 4
-       %tmp345 = getelementptr i32* %tmp341, i32 %tmp344
        br label %bb62

 bb62:
-       %iftmp.62.0.in = phi i32* [ %tmp345, %bb61 ], [ %tmp340, %insn_cuid.exit ]
+       %insn.pn2 = phi %struct.rtx_def* [ %insn, %bb61 ], [ %insn_addr.0.ph.i, %insn_cuid.exit ]
+       %tmp344.pn.in.in = getelementptr %struct.rtx_def* %insn.pn2, i32 0, i32 3
+       %tmp344.pn.in = bitcast [1 x %struct.rtunion]* %tmp344.pn.in.in to i32*
+       %tmp341.pn = load i32** @uid_cuid
+       %tmp344.pn = load i32* %tmp344.pn.in
+       %iftmp.62.0.in = getelementptr i32* %tmp341.pn, i32 %tmp344.pn
        %iftmp.62.0 = load i32* %iftmp.62.0.in



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60325 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../Scalar/InstructionCombining.cpp           | 22 +++++--------------
 1 file changed, 5 insertions(+), 17 deletions(-)

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 49e7fc07ac2..11c5f752977 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -9975,8 +9975,7 @@ Instruction *InstCombiner::transformCallThroughTrampoline(CallSite CS) {
 /// and a single binop.
 Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
   Instruction *FirstInst = cast<Instruction>(PN.getIncomingValue(0));
-  assert(isa<BinaryOperator>(FirstInst) || isa<GetElementPtrInst>(FirstInst) ||
-         isa<CmpInst>(FirstInst));
+  assert(isa<BinaryOperator>(FirstInst) || isa<CmpInst>(FirstInst));
   unsigned Opc = FirstInst->getOpcode();
   Value *LHSVal = FirstInst->getOperand(0);
   Value *RHSVal = FirstInst->getOperand(1);
@@ -10006,14 +10005,7 @@ Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
     if (I->getOperand(1) != RHSVal) RHSVal = 0;
   }
   
-  // Otherwise, this is safe to transform, determine if it is profitable.
-
-  // If this is a GEP, and if the index (not the pointer) needs a PHI, bail out.
-  // Indexes are often folded into load/store instructions, so we don't want to
-  // hide them behind a phi.
-  // URR??
-  if (isa<GetElementPtrInst>(FirstInst) && RHSVal == 0)
-    return 0;
+  // Otherwise, this is safe to transform!
   
   Value *InLHS = FirstInst->getOperand(0);
   Value *InRHS = FirstInst->getOperand(1);
@@ -10053,11 +10045,9 @@ Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
     
   if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
     return BinaryOperator::Create(BinOp->getOpcode(), LHSVal, RHSVal);
-  if (CmpInst *CIOp = dyn_cast<CmpInst>(FirstInst))
-    return CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(), LHSVal, 
-                           RHSVal);
-  assert(isa<GetElementPtrInst>(FirstInst));
-  return GetElementPtrInst::Create(LHSVal, RHSVal);
+  CmpInst *CIOp = cast<CmpInst>(FirstInst);
+  return CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(), LHSVal,
+                         RHSVal);
 }
 
 Instruction *InstCombiner::FoldPHIArgGEPIntoPHI(PHINode &PN) {
@@ -10207,8 +10197,6 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
       return 0;
     
   } else if (isa<GetElementPtrInst>(FirstInst)) {
-    if (FirstInst->getNumOperands() == 2)
-      return FoldPHIArgBinOpIntoPHI(PN);
     return FoldPHIArgGEPIntoPHI(PN);
   } else {
     return 0;  // Cannot fold this operation.
-- 
2.34.1