Changes in directory llvm/lib/CodeGen/SelectionDAG:
DAGCombiner.cpp updated: 1.194 -> 1.195
---
Log message:
Basic "in frame" alias analysis.
---
Diffs of the changes: (+49 -1)
DAGCombiner.cpp | 50 +++++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 49 insertions(+), 1 deletion(-)
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
diff -u llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.194
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.195
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.194 Thu Sep 21 01:40:43 2006
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Thu Sep 21 11:28:59 2006
@@ -35,6 +35,7 @@
#include "llvm/Support/MathExtras.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Support/Compiler.h"
+#include "llvm/Support/CommandLine.h"
#include <algorithm>
#include <cmath>
#include <iostream>
@@ -43,8 +44,17 @@
namespace {
static Statistic<> NodesCombined ("dagcombiner",
"Number of dag nodes combined");
+
- class VISIBILITY_HIDDEN DAGCombiner {
+#ifndef NDEBUG
+static cl::opt<bool>
+ CombinerAA("combiner-alias-analysis", cl::Hidden,
+ cl::desc("Turn on alias analysis turning testing"));
+#else
+ static const bool CombinerAA = 0;
+#endif
+
+class VISIBILITY_HIDDEN DAGCombiner {
SelectionDAG &DAG;
TargetLowering &TLI;
bool AfterLegalize;
@@ -231,6 +241,7 @@
SDOperand BuildSDIV(SDNode *N);
SDOperand BuildUDIV(SDNode *N);
SDNode *MatchRotate(SDOperand LHS, SDOperand RHS);
+ bool isNotAlias(SDOperand Ptr1, SDOperand Ptr2);
public:
DAGCombiner(SelectionDAG &D)
: DAG(D), TLI(D.getTargetLoweringInfo()), AfterLegalize(false) {}
@@ -2577,6 +2588,27 @@
return SDOperand();
}
+/// isNotAlias - Return true if we have definitive knowlege that the two
+/// addresses don't overlap.
+bool DAGCombiner::isNotAlias(SDOperand Ptr1, SDOperand Ptr2) {
+ // Mind the flag.
+ if (!CombinerAA) return false;
+
+ // If they are the same then they are simple aliases.
+ if (Ptr1 == Ptr2) return false;
+
+ // If either operand is a frame value (not the same location from above test)
+ // then they can't alias.
+ FrameIndexSDNode *FI1 = dyn_cast<FrameIndexSDNode>(Ptr1);
+ FrameIndexSDNode *FI2 = dyn_cast<FrameIndexSDNode>(Ptr2);
+ if (FI1 || FI2) {
+ return true;
+ }
+
+ // Otherwise we don't know and have to play it safe.
+ return false;
+}
+
SDOperand DAGCombiner::visitSTORE(SDNode *N) {
SDOperand Chain = N->getOperand(0);
SDOperand Value = N->getOperand(1);
@@ -2607,6 +2639,22 @@
if (0 && Value.getOpcode() == ISD::BIT_CONVERT)
return DAG.getNode(ISD::STORE, MVT::Other, Chain, Value.getOperand(0),
Ptr, SrcValue);
+
+ // If the previous store is not an alias then break artificial chain.
+ if (Chain.getOpcode() == ISD::STORE && isNotAlias(Ptr, Chain.getOperand(2)))
{
+ // Replace the chain to void dependency.
+ SDNode *PrevStore = Chain.Val;
+ SDOperand ReplStore = DAG.getNode(ISD::STORE, MVT::Other,
+ PrevStore->getOperand(0), Value, Ptr,
+ SrcValue);
+ // Create token to keep both stores around.
+ SDOperand Token = DAG.getNode(ISD::TokenFactor, MVT::Other,
+ Chain, ReplStore);
+ // Replace uses with token.
+ CombineTo(N, Token);
+ // Don't recombine on token.
+ return SDOperand(N, 0);
+ }
return SDOperand();
}
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