Changes in directory llvm/lib/CodeGen/SelectionDAG:
DAGCombiner.cpp updated: 1.114 -> 1.115
---
Log message:
Pull shifts by a constant through multiplies (a form of reassociation),
implementing Regression/CodeGen/X86/mul-shift-reassoc.ll
---
Diffs of the changes: (+27 -0)
DAGCombiner.cpp | 27 +++++++++++++++++++++++++++
1 files changed, 27 insertions(+)
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
diff -u llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.114
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.115
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.114 Tue Feb 28 19:09:54 2006
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Tue Feb 28 21:44:24 2006
@@ -726,6 +726,33 @@
DAG.getConstant(Log2_64(-N1C->getSignExtended()),
TLI.getShiftAmountTy())));
}
+
+ // (mul (shl X, c1), c2) -> (mul X, c2 << c1)
+ if (N1C && N0.getOpcode() == ISD::SHL &&
+ isa<ConstantSDNode>(N0.getOperand(1))) {
+ SDOperand C3 = DAG.getNode(ISD::SHL, VT, N1, N0.getOperand(1));
+ return DAG.getNode(ISD::MUL, VT, N0.getOperand(0), C3);
+ }
+
+ // Change (mul (shl X, C), Y) -> (shl (mul X, Y), C) when the shift has one
+ // use.
+ {
+ SDOperand Sh(0,0), Y(0,0);
+ // Check for both (mul (shl X, C), Y) and (mul Y, (shl X, C)).
+ if (N0.getOpcode() == ISD::SHL && isa<ConstantSDNode>(N0.getOperand(1)) &&
+ N0.Val->hasOneUse()) {
+ Sh = N0; Y = N1;
+ } else if (N1.getOpcode() == ISD::SHL &&
+ isa<ConstantSDNode>(N1.getOperand(1)) && N1.Val->hasOneUse()) {
+ Sh = N1; Y = N0;
+ }
+ if (Sh.Val) {
+ SDOperand Mul = DAG.getNode(ISD::MUL, VT, Sh.getOperand(0), Y);
+ return DAG.getNode(ISD::SHL, VT, Mul, Sh.getOperand(1));
+ }
+ }
+
+
// reassociate mul
SDOperand RMUL = ReassociateOps(ISD::MUL, N0, N1);
if (RMUL.Val != 0)
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