[llvm-commits] [llvm] r54786 - in /llvm/trunk: lib/Transforms/Scalar/LoopStrengthReduce.cpp test/Transforms/LoopStrengthReduce/2008-08-14-ShadowIV.ll
Devang Patel
dpatel at apple.com
Thu Aug 14 13:58:31 PDT 2008
Author: dpatel
Date: Thu Aug 14 15:58:31 2008
New Revision: 54786
URL: http://llvm.org/viewvc/llvm-project?rev=54786&view=rev
Log:
If IV is used in a int-to-float cast inside the loop then try to eliminate the cast opeation.
Added:
llvm/trunk/test/Transforms/LoopStrengthReduce/2008-08-14-ShadowIV.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp?rev=54786&r1=54785&r2=54786&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp Thu Aug 14 15:58:31 2008
@@ -45,6 +45,7 @@
STATISTIC(NumInserted, "Number of PHIs inserted");
STATISTIC(NumVariable, "Number of PHIs with variable strides");
STATISTIC(NumEliminated , "Number of strides eliminated");
+STATISTIC(NumShadow , "Number of Shdow IVs optimized");
namespace {
@@ -177,6 +178,10 @@
IVStrideUse* &CondUse,
const SCEVHandle* &CondStride);
void OptimizeIndvars(Loop *L);
+
+ /// OptimizeShadowIV - If IV is used in a int-to-float cast
+ /// inside the loop then try to eliminate the cast opeation.
+ void OptimizeShadowIV(Loop *L);
bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
const SCEVHandle *&CondStride);
bool RequiresTypeConversion(const Type *Ty, const Type *NewTy);
@@ -1689,12 +1694,108 @@
return Cond;
}
+/// OptimizeShadowIV - If IV is used in a int-to-float cast
+/// inside the loop then try to eliminate the cast opeation.
+void LoopStrengthReduce::OptimizeShadowIV(Loop *L) {
+
+ for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e;
+ ++Stride) {
+ std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
+ IVUsesByStride.find(StrideOrder[Stride]);
+ assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
+
+ for (std::vector<IVStrideUse>::iterator UI = SI->second.Users.begin(),
+ E = SI->second.Users.end(); UI != E; /* empty */) {
+ std::vector<IVStrideUse>::iterator CandidateUI = UI;
+ UI++;
+ Instruction *ShadowUse = CandidateUI->User;
+ const Type *DestTy = NULL;
+
+ /* If shadow use is a int->float cast then insert a second IV
+ to elminate this cast.
+
+ for (unsigned i = 0; i < n; ++i)
+ foo((double)i);
+
+ is trnasformed into
+
+ double d = 0.0;
+ for (unsigned i = 0; i < n; ++i, ++d)
+ foo(d);
+ */
+ UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->User);
+ if (UCast)
+ DestTy = UCast->getDestTy();
+ else {
+ SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->User);
+ if (!SCast) continue;
+ DestTy = SCast->getDestTy();
+ }
+
+ PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
+ if (!PH) continue;
+ if (PH->getNumIncomingValues() != 2) continue;
+
+ unsigned Entry, Latch;
+ if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
+ Entry = 0;
+ Latch = 1;
+ } else {
+ Entry = 1;
+ Latch = 0;
+ }
+
+ ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
+ if (!Init) continue;
+ ConstantFP *NewInit = ConstantFP::get(DestTy, Init->getZExtValue());
+
+ BinaryOperator *Incr =
+ dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
+ if (!Incr) continue;
+ if (Incr->getOpcode() != Instruction::Add
+ && Incr->getOpcode() != Instruction::Sub)
+ continue;
+
+ /* Initialize new IV, double d = 0.0 in above example. */
+ ConstantInt *C = NULL;
+ if (Incr->getOperand(0) == PH)
+ C = dyn_cast<ConstantInt>(Incr->getOperand(1));
+ else if (Incr->getOperand(1) == PH)
+ C = dyn_cast<ConstantInt>(Incr->getOperand(0));
+ else
+ continue;
+
+ if (!C) continue;
+
+ /* create new icnrement. '++d' in above example. */
+ ConstantFP *CFP = ConstantFP::get(DestTy, C->getZExtValue());
+ BinaryOperator *NewIncr =
+ BinaryOperator::Create(Incr->getOpcode(),
+ NewInit, CFP, "IV.S.next.", Incr);
+
+ /* Add new PHINode. */
+ PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH);
+ NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
+ NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
+
+ /* Remove cast operation */
+ ShadowUse->replaceAllUsesWith(NewPH);
+ ShadowUse->eraseFromParent();
+ SI->second.Users.erase(CandidateUI);
+ NumShadow++;
+ break;
+ }
+ }
+}
+
// OptimizeIndvars - Now that IVUsesByStride is set up with all of the indvar
// uses in the loop, look to see if we can eliminate some, in favor of using
// common indvars for the different uses.
void LoopStrengthReduce::OptimizeIndvars(Loop *L) {
// TODO: implement optzns here.
+ OptimizeShadowIV(L);
+
// Finally, get the terminating condition for the loop if possible. If we
// can, we want to change it to use a post-incremented version of its
// induction variable, to allow coalescing the live ranges for the IV into
Added: llvm/trunk/test/Transforms/LoopStrengthReduce/2008-08-14-ShadowIV.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopStrengthReduce/2008-08-14-ShadowIV.ll?rev=54786&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopStrengthReduce/2008-08-14-ShadowIV.ll (added)
+++ llvm/trunk/test/Transforms/LoopStrengthReduce/2008-08-14-ShadowIV.ll Thu Aug 14 15:58:31 2008
@@ -0,0 +1,27 @@
+; RUN: llvm-as < %s | opt -loop-reduce | llvm-dis | grep "phi double"
+
+define void @foobar(i32 %n) nounwind {
+entry:
+ icmp eq i32 %n, 0 ; <i1>:0 [#uses=2]
+ br i1 %0, label %return, label %bb.nph
+
+bb.nph: ; preds = %entry
+ %umax = select i1 %0, i32 1, i32 %n ; <i32> [#uses=1]
+ br label %bb
+
+bb: ; preds = %bb, %bb.nph
+ %i.03 = phi i32 [ 0, %bb.nph ], [ %indvar.next, %bb ] ; <i32> [#uses=3]
+ tail call void @bar( i32 %i.03 ) nounwind
+ uitofp i32 %i.03 to double ; <double>:1 [#uses=1]
+ tail call void @foo( double %1 ) nounwind
+ %indvar.next = add i32 %i.03, 1 ; <i32> [#uses=2]
+ %exitcond = icmp eq i32 %indvar.next, %umax ; <i1> [#uses=1]
+ br i1 %exitcond, label %return, label %bb
+
+return: ; preds = %bb, %entry
+ ret void
+}
+
+declare void @bar(i32)
+
+declare void @foo(double)
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