[llvm-commits] [llvm] r60325 - /llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp

[Chris Lattner]

Author: lattner
Date: Sun Nov 30 21:42:51 2008
New Revision: 60325

URL: http://llvm.org/viewvc/llvm-project?rev=60325&view=rev
Log:
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     


Modified:
    llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=60325&r1=60324&r2=60325&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Sun Nov 30 21:42:51 2008
@@ -9975,8 +9975,7 @@
 /// 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 @@
     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 @@
     
   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 @@
       return 0;
     
   } else if (isa<GetElementPtrInst>(FirstInst)) {
-    if (FirstInst->getNumOperands() == 2)
-      return FoldPHIArgBinOpIntoPHI(PN);
     return FoldPHIArgGEPIntoPHI(PN);
   } else {
     return 0;  // Cannot fold this operation.