Changes in directory llvm/lib/CodeGen/SelectionDAG:
DAGCombiner.cpp updated: 1.206 -> 1.207
---
Log message:
Alias analysis code clean ups.
---
Diffs of the changes: (+146 -163)
DAGCombiner.cpp | 309 ++++++++++++++++++++++++++------------------------------
1 files changed, 146 insertions(+), 163 deletions(-)
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
diff -u llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.206
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.207
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.206 Wed Oct 4 11:53:27 2006
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Thu Oct 5 10:07:25 2006
@@ -51,6 +51,84 @@
CombinerAA("combiner-alias-analysis", cl::Hidden,
cl::desc("Turn on alias analysis turning testing"));
+
+/// FindBaseOffset - Return true if base is known not to alias with anything
+/// but itself. Provides base object and offset as results.
+bool FindBaseOffset(SDOperand Ptr, SDOperand &Object, int64_t &Offset) {
+ // If it's an adding or subtracting a simple constant then add the constant
+ // to the offset.
+ if (Ptr.getOpcode() == ISD::ADD) {
+ if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Ptr.getOperand(1))) {
+ bool IsNonAliasing = FindBaseOffset(Ptr.getOperand(0), Object, Offset);
+ Offset += C->getValue();
+ return IsNonAliasing;
+ }
+ } else if (Ptr.getOpcode() == ISD::SUB) {
+ // FIXME - Aren't all subtract constants converted to add negative constant.
+ if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Ptr.getOperand(1))) {
+ bool IsNonAliasing = FindBaseOffset(Ptr.getOperand(0), Object, Offset);
+ Offset -= C->getValue();
+ return IsNonAliasing;
+ }
+ }
+
+ // Primitive operation.
+ Object = Ptr; Offset = 0;
+
+ // If it's any of the following then it can't alias with anything but itself.
+ return isa<FrameIndexSDNode>(Ptr) ||
+ isa<ConstantPoolSDNode>(Ptr) ||
+ isa<GlobalAddressSDNode>(Ptr);
+}
+
+/// isAlias - Return true if there is any possibility that the two addresses
+/// overlap.
+bool isAlias(SDOperand Ptr1, int64_t Size1, SDOperand SrcValue1,
+ SDOperand Ptr2, int64_t Size2, SDOperand SrcValue2) {
+ // If they are the same then they must be aliases.
+ if (Ptr1 == Ptr2) return true;
+
+ // Gather base node and offset information.
+ SDOperand Object1, Object2;
+ int64_t Offset1, Offset2;
+ bool IsNonAliasing1 = FindBaseOffset(Ptr1, Object1, Offset1);
+ bool IsNonAliasing2 = FindBaseOffset(Ptr2, Object2, Offset2);
+
+ // If they have a same base address then...
+ if (Object1 == Object2) {
+ // Check to see if the addresses overlap.
+ return !((Offset1 + Size1) <= Offset2 || (Offset2 + Size2) <= Offset1);
+ }
+
+ // Otherwise they alias if they are both non aliasing.
+ return !IsNonAliasing1 && IsNonAliasing2;
+}
+
+/// FindAliasInfo - Extracts the relevant alias information from the memory
+/// node. Returns true if the operand was a load.
+bool FindAliasInfo(SDNode *N,
+ SDOperand &Ptr, int64_t &Size, SDOperand &SrcValue) {
+ switch (N->getOpcode()) {
+ case ISD::LOAD:
+ Ptr = N->getOperand(1);
+ Size = MVT::getSizeInBits(N->getValueType(0)) >> 3;
+ SrcValue = N->getOperand(2);
+ return true;
+ case ISD::STORE:
+ Ptr = N->getOperand(2);
+ Size = MVT::getSizeInBits(N->getOperand(1).getValueType()) >> 3;
+ SrcValue = N->getOperand(3);
+ return false;
+ default:
+ assert(0 && "FindAliasInfo expected a memory operand");
+ return false;
+ }
+
+ return false;
+}
+
+//------------------------------ DAGCombiner
---------------------------------//
+
class VISIBILITY_HIDDEN DAGCombiner {
SelectionDAG &DAG;
TargetLowering &TLI;
@@ -243,24 +321,9 @@
SDOperand BuildUDIV(SDNode *N);
SDNode *MatchRotate(SDOperand LHS, SDOperand RHS);
- /// FindBaseOffset - Return true if base is known not to alias with
anything
- /// but itself. Provides base object and offset as results.
- static bool FindBaseOffset(SDOperand Ptr,
- SDOperand &Object, int64_t &Offset);
-
- /// isAlias - Return true if there is any possibility that the two
addresses
- /// overlap.
- static bool isAlias(SDOperand Ptr1, int64_t Size1, SDOperand SrcValue1,
- SDOperand Ptr2, int64_t Size2, SDOperand SrcValue2);
-
- /// FindAliasInfo - Extracts the relevant alias information from the memory
- /// node.
- static void FindAliasInfo(SDNode *N,
- SDOperand &Ptr, int64_t &Size, SDOperand &SrcValue);
-
/// GatherAllAliases - Walk up chain skipping non-aliasing memory nodes,
/// looking for aliasing nodes and adding them to the Aliases vector.
- void GatherAllAliases(SDNode *N, SDOperand Chain,
+ void GatherAllAliases(SDNode *N, SDOperand OriginalChain,
SmallVector<SDOperand, 8> &Aliases);
/// FindBetterChain - Walk up chain skipping non-aliasing memory nodes,
@@ -457,8 +520,6 @@
DAG.DeleteNode(N);
}
}
-
-// DetectCycle();
}
// If the root changed (e.g. it was a dead load, update the root).
@@ -538,31 +599,29 @@
SmallVector<SDNode *, 8> TFs; // List of token factors to visit.
SmallVector<SDOperand, 8> Ops; // Ops for replacing token factor.
bool Changed = false; // If we should replace this token factor.
- std::set<SDNode *> Visited; // Visited node set.
// Start out with this token factor.
TFs.push_back(N);
- while (!TFs.empty()) {
- SDNode *TF = TFs.back();
- TFs.pop_back();
-
+ // Iterate through token factors. The TFs grows a new token factors are
+ // encountered.
+ for (unsigned i = 0; i < TFs.size(); ++i) {
+ SDNode *TF = TFs[i];
+
// Check each of the operands.
for (unsigned i = 0, ie = TF->getNumOperands(); i != ie; ++i) {
SDOperand Op = TF->getOperand(i);
- // Don't bother if we've seen this node before.
- if (Visited.find(Op.Val) != Visited.end()) continue;
- Visited.insert(Op.Val);
-
switch (Op.getOpcode()) {
case ISD::EntryToken:
- // Entry tokens don't need to be added to the list (picked up later.)
+ // Entry tokens don't need to be added to the list. They are
+ // rededundant.
+ Changed = true;
break;
case ISD::TokenFactor:
- // FIXME - Old code only merged when use of one.
- if (CombinerAA || Op.hasOneUse()) {
+ if ((CombinerAA || Op.hasOneUse()) &&
+ std::find(TFs.begin(), TFs.end(), Op.Val) == TFs.end()) {
// Queue up for processing.
TFs.push_back(Op.Val);
// Clean up in case the token factor is removed.
@@ -573,8 +632,9 @@
// Fall thru
default:
- Ops.push_back(Op);
- Changed = true;
+ // Only add if not there prior.
+ if (std::find(Ops.begin(), Ops.end(), Op) == Ops.end())
+ Ops.push_back(Op);
break;
}
}
@@ -3922,151 +3982,74 @@
return S;
}
-/// FindBaseOffset - Return true if base is known not to alias with anything
-/// but itself. Provides base object and offset as results.
-bool DAGCombiner::FindBaseOffset(SDOperand Ptr,
- SDOperand &Object, int64_t &Offset) {
- // If it's an adding or subtracting a simple constant then add the constant
- // to the offset.
- if (Ptr.getOpcode() == ISD::ADD) {
- if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Ptr.getOperand(1))) {
- bool IsNonAliasing = FindBaseOffset(Ptr.getOperand(0), Object, Offset);
- Offset += C->getValue();
- return IsNonAliasing;
- }
- } else if (Ptr.getOpcode() == ISD::SUB) {
- // FIXME - Aren't all subtract constants converted to add negative constant.
- if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Ptr.getOperand(1))) {
- bool IsNonAliasing = FindBaseOffset(Ptr.getOperand(0), Object, Offset);
- Offset -= C->getValue();
- return IsNonAliasing;
- }
- }
-
- // Primitive operation.
- Object = Ptr; Offset = 0;
-
- // If it's any of the following then it can't alias with anything but itself.
- return isa<FrameIndexSDNode>(Ptr) ||
- isa<ConstantPoolSDNode>(Ptr) ||
- isa<GlobalAddressSDNode>(Ptr);
-}
-
-/// isAlias - Return true if there is any possibility that the two addresses
-/// overlap.
-bool DAGCombiner::isAlias(SDOperand Ptr1, int64_t Size1,
- SDOperand SrcValue1,
- SDOperand Ptr2, int64_t Size2,
- SDOperand SrcValue2) {
- // If they are the same then they must be aliases.
- if (Ptr1 == Ptr2) return true;
-
- // Gather base node and offset information.
- SDOperand Object1, Object2;
- int64_t Offset1, Offset2;
- bool IsNonAliasing1 = FindBaseOffset(Ptr1, Object1, Offset1);
- bool IsNonAliasing2 = FindBaseOffset(Ptr2, Object2, Offset2);
-
- // If they have a same base address then...
- if (Object1 == Object2) {
- // Check to see if the addresses overlap.
- return !((Offset1 + Size1) <= Offset2 || (Offset2 + Size2) <= Offset1);
- }
-
- // Otherwise they alias if they are both non aliasing.
- return !IsNonAliasing1 && IsNonAliasing2;
-}
-
-/// FindAliasInfo - Extracts the relevant alias information from the memory
-/// node.
-void DAGCombiner::FindAliasInfo(SDNode *N,
- SDOperand &Ptr, int64_t &Size, SDOperand &SrcValue) {
- switch (N->getOpcode()) {
- case ISD::LOAD:
- Ptr = N->getOperand(1);
- Size = MVT::getSizeInBits(N->getValueType(0)) >> 3;
- SrcValue = N->getOperand(2);
- break;
- case ISD::STORE:
- Ptr = N->getOperand(2);
- Size = MVT::getSizeInBits(N->getOperand(1).getValueType()) >> 3;
- SrcValue = N->getOperand(3);
- break;
- default:
- assert(0 && "FindAliasInfo expected a memory operand");
- }
-}
-
/// GatherAllAliases - Walk up chain skipping non-aliasing memory nodes,
/// looking for aliasing nodes and adding them to the Aliases vector.
-void DAGCombiner::GatherAllAliases(SDNode *N, SDOperand Chain,
+void DAGCombiner::GatherAllAliases(SDNode *N, SDOperand OriginalChain,
SmallVector<SDOperand, 8> &Aliases) {
- SmallVector<SDOperand, 8> Ops; // List of operands to visit.
+ SmallVector<SDOperand, 8> Chains; // List of chains to visit.
std::set<SDNode *> Visited; // Visited node set.
// Get alias information for node.
SDOperand Ptr;
int64_t Size;
SDOperand SrcValue;
- FindAliasInfo(N, Ptr, Size, SrcValue);
+ bool IsLoad = FindAliasInfo(N, Ptr, Size, SrcValue);
// Starting off.
- Ops.push_back(Chain);
+ Chains.push_back(OriginalChain);
- // While there are nodes to process.
- while (!Ops.empty()) {
- SDOperand Op = Ops.back();
- Ops.pop_back();
-
- for (bool Done = false; !Done;) {
- // Don't bother if we've been before.
- if (Visited.find(Op.Val) != Visited.end()) break;
- Visited.insert(Op.Val);
-
- // Assume we're done.
- Done = true;
-
- switch (Op.getOpcode()) {
- case ISD::EntryToken:
- // Entry token is ideal chain operand, but handled in FindBetterChain.
- break;
-
- case ISD::LOAD:
- case ISD::STORE: {
- // Get alias information for Op.
- SDOperand OpPtr;
- int64_t OpSize;
- SDOperand OpSrcValue;
- FindAliasInfo(Op.Val, OpPtr, OpSize, OpSrcValue);
-
- // If chain is alias then stop here.
- if (isAlias(Ptr, Size, SrcValue, OpPtr, OpSize, OpSrcValue)) {
- Aliases.push_back(Op);
- } else {
- // Otherwise walk up the chain.
- // Clean up old chain.
- AddToWorkList(Op.Val);
- // Try up further.
- Op = Op.getOperand(0);
- // We're not done yet.
- Done = false;
- }
- break;
- }
+ // Look at each chain and determine if it is an alias. If so, add it to the
+ // aliases list. If not, then continue up the chain looking for the next
+ // candidate.
+ while (!Chains.empty()) {
+ SDOperand Chain = Chains.back();
+ Chains.pop_back();
+
+ // Don't bother if we've been before.
+ if (Visited.find(Chain.Val) != Visited.end()) continue;
+ Visited.insert(Chain.Val);
+
+ switch (Chain.getOpcode()) {
+ case ISD::EntryToken:
+ // Entry token is ideal chain operand, but handled in FindBetterChain.
+ break;
- case ISD::TokenFactor:
- // Queue up operands in reverse order to maintain prior order.
- for (unsigned n = Op.getNumOperands(); n;)
- Ops.push_back(Op.getOperand(--n));
- // Eliminate the token factor if we can.
- AddToWorkList(Op.Val);
- break;
-
- default:
- // For all other instructions we will just have to take what we can
get.
- Aliases.push_back(Op);
- break;
+ case ISD::LOAD:
+ case ISD::STORE: {
+ // Get alias information for Chain.
+ SDOperand OpPtr;
+ int64_t OpSize;
+ SDOperand OpSrcValue;
+ bool IsOpLoad = FindAliasInfo(Chain.Val, OpPtr, OpSize, OpSrcValue);
+
+ // If chain is alias then stop here.
+ if (!(IsLoad && IsOpLoad) &&
+ isAlias(Ptr, Size, SrcValue, OpPtr, OpSize, OpSrcValue)) {
+ Aliases.push_back(Chain);
+ } else {
+ // Look further up the chain.
+ Chains.push_back(Chain.getOperand(0));
+ // Clean up old chain.
+ AddToWorkList(Chain.Val);
}
+ break;
+ }
+
+ case ISD::TokenFactor:
+ // We have to check each of the operands of the token factor, so we queue
+ // then up. Adding the operands to the queue (stack) in reverse order
+ // maintains the original order and increases the likelihood that getNode
+ // will find a matching token factor (CSE.)
+ for (unsigned n = Chain.getNumOperands(); n;)
+ Chains.push_back(Chain.getOperand(--n));
+ // Eliminate the token factor if we can.
+ AddToWorkList(Chain.Val);
+ break;
+
+ default:
+ // For all other instructions we will just have to take what we can get.
+ Aliases.push_back(Chain);
+ break;
}
}
}
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