Changes in directory llvm/lib/Transforms/Scalar:
InstructionCombining.cpp updated: 1.437 -> 1.438
---
Log message:
Fix a problem that Nate noticed that boils down to an over conservative check
in the code that does "select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y)))".
We now compile this loop:
LBB1_1: ; no_exit
add r6, r2, r3
subf r3, r2, r3
cmpwi cr0, r2, 0
addi r7, r5, 4
lwz r2, 0(r5)
addi r4, r4, 1
blt cr0, LBB1_4 ; no_exit
LBB1_3: ; no_exit
mr r3, r6
LBB1_4: ; no_exit
cmpwi cr0, r4, 16
mr r5, r7
bne cr0, LBB1_1 ; no_exit
into this instead:
LBB1_1: ; no_exit
srawi r6, r2, 31
add r2, r2, r6
xor r6, r2, r6
addi r7, r5, 4
lwz r2, 0(r5)
addi r4, r4, 1
add r3, r3, r6
cmpwi cr0, r4, 16
mr r5, r7
bne cr0, LBB1_1 ; no_exit
---
Diffs of the changes: (+18 -23)
InstructionCombining.cpp | 41 ++++++++++++++++++-----------------------
1 files changed, 18 insertions(+), 23 deletions(-)
Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.437
llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.438
--- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.437 Fri Feb 17
21:20:33 2006
+++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp Fri Feb 24 12:05:58 2006
@@ -5074,30 +5074,25 @@
}
if (OtherAddOp) {
- // So at this point we know we have:
- // select C, (add X, Y), (sub X, ?)
- // We can do the transform profitably if either 'Y' = '?' or '?' is
- // a constant.
- if (SubOp->getOperand(1) == AddOp ||
- isa<Constant>(SubOp->getOperand(1))) {
- Value *NegVal;
- if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) {
- NegVal = ConstantExpr::getNeg(C);
- } else {
- NegVal = InsertNewInstBefore(
- BinaryOperator::createNeg(SubOp->getOperand(1)),
SI);
- }
-
- Value *NewTrueOp = OtherAddOp;
- Value *NewFalseOp = NegVal;
- if (AddOp != TI)
- std::swap(NewTrueOp, NewFalseOp);
- Instruction *NewSel =
- new SelectInst(CondVal,
NewTrueOp,NewFalseOp,SI.getName()+".p");
-
- NewSel = InsertNewInstBefore(NewSel, SI);
- return BinaryOperator::createAdd(SubOp->getOperand(0), NewSel);
+ // So at this point we know we have (Y -> OtherAddOp):
+ // select C, (add X, Y), (sub X, Z)
+ Value *NegVal; // Compute -Z
+ if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) {
+ NegVal = ConstantExpr::getNeg(C);
+ } else {
+ NegVal = InsertNewInstBefore(
+ BinaryOperator::createNeg(SubOp->getOperand(1), "tmp"),
SI);
}
+
+ Value *NewTrueOp = OtherAddOp;
+ Value *NewFalseOp = NegVal;
+ if (AddOp != TI)
+ std::swap(NewTrueOp, NewFalseOp);
+ Instruction *NewSel =
+ new SelectInst(CondVal, NewTrueOp,NewFalseOp,SI.getName()+".p");
+
+ NewSel = InsertNewInstBefore(NewSel, SI);
+ return BinaryOperator::createAdd(SubOp->getOperand(0), NewSel);
}
}
}
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