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Basic "in frame" alias analysis.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30568 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -35,6 +35,7 @@
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#include "llvm/Support/MathExtras.h"
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#include "llvm/Target/TargetLowering.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/CommandLine.h"
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#include <algorithm>
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#include <cmath>
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#include <iostream>
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@ -43,8 +44,17 @@ using namespace llvm;
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namespace {
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static Statistic<> NodesCombined ("dagcombiner",
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"Number of dag nodes combined");
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class VISIBILITY_HIDDEN DAGCombiner {
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#ifndef NDEBUG
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static cl::opt<bool>
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CombinerAA("combiner-alias-analysis", cl::Hidden,
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cl::desc("Turn on alias analysis turning testing"));
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#else
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static const bool CombinerAA = 0;
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#endif
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class VISIBILITY_HIDDEN DAGCombiner {
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SelectionDAG &DAG;
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TargetLowering &TLI;
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bool AfterLegalize;
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@ -231,6 +241,7 @@ namespace {
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SDOperand BuildSDIV(SDNode *N);
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SDOperand BuildUDIV(SDNode *N);
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SDNode *MatchRotate(SDOperand LHS, SDOperand RHS);
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bool isNotAlias(SDOperand Ptr1, SDOperand Ptr2);
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public:
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DAGCombiner(SelectionDAG &D)
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: DAG(D), TLI(D.getTargetLoweringInfo()), AfterLegalize(false) {}
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@ -2577,6 +2588,27 @@ SDOperand DAGCombiner::visitXEXTLOAD(SDNode *N) {
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return SDOperand();
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}
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/// isNotAlias - Return true if we have definitive knowlege that the two
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/// addresses don't overlap.
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bool DAGCombiner::isNotAlias(SDOperand Ptr1, SDOperand Ptr2) {
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// Mind the flag.
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if (!CombinerAA) return false;
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// If they are the same then they are simple aliases.
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if (Ptr1 == Ptr2) return false;
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// If either operand is a frame value (not the same location from above test)
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// then they can't alias.
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FrameIndexSDNode *FI1 = dyn_cast<FrameIndexSDNode>(Ptr1);
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FrameIndexSDNode *FI2 = dyn_cast<FrameIndexSDNode>(Ptr2);
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if (FI1 || FI2) {
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return true;
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}
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// Otherwise we don't know and have to play it safe.
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return false;
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}
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SDOperand DAGCombiner::visitSTORE(SDNode *N) {
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SDOperand Chain = N->getOperand(0);
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SDOperand Value = N->getOperand(1);
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@ -2607,6 +2639,22 @@ SDOperand DAGCombiner::visitSTORE(SDNode *N) {
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if (0 && Value.getOpcode() == ISD::BIT_CONVERT)
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return DAG.getNode(ISD::STORE, MVT::Other, Chain, Value.getOperand(0),
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Ptr, SrcValue);
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// If the previous store is not an alias then break artificial chain.
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if (Chain.getOpcode() == ISD::STORE && isNotAlias(Ptr, Chain.getOperand(2))) {
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// Replace the chain to void dependency.
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SDNode *PrevStore = Chain.Val;
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SDOperand ReplStore = DAG.getNode(ISD::STORE, MVT::Other,
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PrevStore->getOperand(0), Value, Ptr,
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SrcValue);
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// Create token to keep both stores around.
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SDOperand Token = DAG.getNode(ISD::TokenFactor, MVT::Other,
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Chain, ReplStore);
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// Replace uses with token.
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CombineTo(N, Token);
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// Don't recombine on token.
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return SDOperand(N, 0);
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}
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return SDOperand();
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}
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