[llvm-commits] CVS: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
Chris Lattner
lattner at cs.uiuc.edu
Mon Oct 10 15:04:59 PDT 2005
Changes in directory llvm/lib/CodeGen/SelectionDAG:
DAGCombiner.cpp updated: 1.27 -> 1.28
---
Log message:
Add support for CombineTo, allowing the dag combiner to replace nodes with
multiple results.
Use this support to implement trivial store->load forwarding, implementing
CodeGen/PowerPC/store-load-fwd.ll. Though this is the most simple case and
can be extended in the future, it is still useful. For example, it speeds
up 197.parser by 6.2% by avoiding an LSU reject in xalloc:
stw r6, lo16(l5_end_of_array)(r2)
addi r2, r5, -4
stwx r5, r4, r2
- lwzx r5, r4, r2
- rlwinm r5, r5, 0, 0, 30
stwx r5, r4, r2
lwz r2, -4(r4)
ori r2, r2, 1
---
Diffs of the changes: (+56 -2)
DAGCombiner.cpp | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++--
1 files changed, 56 insertions(+), 2 deletions(-)
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
diff -u llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.27 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.28
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.27 Mon Oct 10 16:26:48 2005
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Mon Oct 10 17:04:48 2005
@@ -23,7 +23,6 @@
// FIXME: select C, pow2, pow2 -> something smart
// FIXME: trunc(select X, Y, Z) -> select X, trunc(Y), trunc(Z)
// FIXME: (select C, load A, load B) -> load (select C, A, B)
-// FIXME: store -> load -> forward substitute
// FIXME: Dead stores -> nuke
// FIXME: shr X, (and Y,31) -> shr X, Y
// FIXME: TRUNC (LOAD) -> EXT_LOAD/LOAD(smaller)
@@ -36,6 +35,7 @@
// FIXME: divide by zero is currently left unfolded. do we want to turn this
// into an undef?
// FIXME: select ne (select cc, 1, 0), 0, true, false -> select cc, true, false
+// FIXME: reassociate (X+C)+Y into (X+Y)+C if the inner expression has one use
//
//===----------------------------------------------------------------------===//
@@ -76,6 +76,37 @@
WorkList.end());
}
+ SDOperand CombineTo(SDNode *N, const std::vector<SDOperand> &To) {
+ DEBUG(std::cerr << "\nReplacing "; N->dump();
+ std::cerr << "\nWith: "; To[0].Val->dump();
+ std::cerr << " and " << To.size()-1 << " other values\n");
+ std::vector<SDNode*> NowDead;
+ DAG.ReplaceAllUsesWith(N, To, &NowDead);
+
+ // Push the new nodes and any users onto the worklist
+ for (unsigned i = 0, e = To.size(); i != e; ++i) {
+ WorkList.push_back(To[i].Val);
+ AddUsersToWorkList(To[i].Val);
+ }
+
+ // Nodes can end up on the worklist more than once. Make sure we do
+ // not process a node that has been replaced.
+ removeFromWorkList(N);
+ for (unsigned i = 0, e = NowDead.size(); i != e; ++i)
+ removeFromWorkList(NowDead[i]);
+
+ // Finally, since the node is now dead, remove it from the graph.
+ DAG.DeleteNode(N);
+ return SDOperand(N, 0);
+ }
+
+ SDOperand CombineTo(SDNode *N, SDOperand Res0, SDOperand Res1) {
+ std::vector<SDOperand> To;
+ To.push_back(Res0);
+ To.push_back(Res1);
+ return CombineTo(N, To);
+ }
+
/// visit - call the node-specific routine that knows how to fold each
/// particular type of node.
SDOperand visit(SDNode *N);
@@ -84,6 +115,7 @@
// node types. The semantics are as follows:
// Return Value:
// SDOperand.Val == 0 - No change was made
+ // SDOperand.Val == N - N was replaced, is dead, and is already handled.
// otherwise - N should be replaced by the returned Operand.
//
SDOperand visitTokenFactor(SDNode *N);
@@ -132,6 +164,8 @@
SDOperand visitBR_CC(SDNode *N);
SDOperand visitBRTWOWAY_CC(SDNode *N);
+ SDOperand visitLOAD(SDNode *N);
+
SDOperand SimplifySelect(SDOperand N0, SDOperand N1, SDOperand N2);
SDOperand SimplifySelectCC(SDOperand N0, SDOperand N1, SDOperand N2,
SDOperand N3, ISD::CondCode CC);
@@ -334,7 +368,8 @@
DEBUG(std::cerr << "\nReplacing "; N->dump();
std::cerr << "\nWith: "; RV.Val->dump();
std::cerr << '\n');
- DAG.ReplaceAllUsesWith(N, std::vector<SDOperand>(1, RV));
+ std::vector<SDNode*> NowDead;
+ DAG.ReplaceAllUsesWith(N, std::vector<SDOperand>(1, RV), &NowDead);
// Push the new node and any users onto the worklist
WorkList.push_back(RV.Val);
@@ -343,6 +378,8 @@
// Nodes can end up on the worklist more than once. Make sure we do
// not process a node that has been replaced.
removeFromWorkList(N);
+ for (unsigned i = 0, e = NowDead.size(); i != e; ++i)
+ removeFromWorkList(NowDead[i]);
// Finally, since the node is now dead, remove it from the graph.
DAG.DeleteNode(N);
@@ -401,6 +438,7 @@
case ISD::BRCONDTWOWAY: return visitBRCONDTWOWAY(N);
case ISD::BR_CC: return visitBR_CC(N);
case ISD::BRTWOWAY_CC: return visitBRTWOWAY_CC(N);
+ case ISD::LOAD: return visitLOAD(N);
}
return SDOperand();
}
@@ -1513,6 +1551,22 @@
return SDOperand();
}
+SDOperand DAGCombiner::visitLOAD(SDNode *N) {
+ SDOperand Chain = N->getOperand(0);
+ SDOperand Ptr = N->getOperand(1);
+ SDOperand SrcValue = N->getOperand(2);
+
+ // If this load is directly stored, replace the load value with the stored
+ // value.
+ // TODO: Handle store large -> read small portion.
+ // TODO: Handle TRUNCSTORE/EXTLOAD
+ if (Chain.getOpcode() == ISD::STORE && Chain.getOperand(2) == Ptr &&
+ Chain.getOperand(1).getValueType() == N->getValueType(0))
+ return CombineTo(N, Chain.getOperand(1), Chain);
+
+ return SDOperand();
+}
+
SDOperand DAGCombiner::SimplifySelect(SDOperand N0, SDOperand N1, SDOperand N2){
assert(N0.getOpcode() ==ISD::SETCC && "First argument must be a SetCC node!");
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