Don't break the IV update in TLI::SimplifySetCC().
LSR always tries to make the ICmp in the loop latch use the incremented
induction variable. This allows the induction variable to be kept in a
single register.
When the induction variable limit is equal to the stride,
SimplifySetCC() would break LSR's hard work by transforming:
(icmp (add iv, stride), stride) --> (cmp iv, 0)
This forced us to use lea for the IC update, preventing the simpler
incl+cmp.
<rdar://problem/7643606>
<rdar://problem/11184260>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154119 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index eefb9e8..03aed3a 100644
--- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -2471,6 +2471,10 @@
}
}
+ // If RHS is a legal immediate value for a compare instruction, we need
+ // to be careful about increasing register pressure needlessly.
+ bool LegalRHSImm = false;
+
if (ConstantSDNode *RHSC = dyn_cast<ConstantSDNode>(N1)) {
if (ConstantSDNode *LHSR = dyn_cast<ConstantSDNode>(N0.getOperand(1))) {
// Turn (X+C1) == C2 --> X == C2-C1
@@ -2505,25 +2509,33 @@
Cond);
}
}
+
+ // Could RHSC fold directly into a compare?
+ if (RHSC->getValueType(0).getSizeInBits() <= 64)
+ LegalRHSImm = isLegalICmpImmediate(RHSC->getSExtValue());
}
// Simplify (X+Z) == X --> Z == 0
- if (N0.getOperand(0) == N1)
- return DAG.getSetCC(dl, VT, N0.getOperand(1),
- DAG.getConstant(0, N0.getValueType()), Cond);
- if (N0.getOperand(1) == N1) {
- if (DAG.isCommutativeBinOp(N0.getOpcode()))
- return DAG.getSetCC(dl, VT, N0.getOperand(0),
- DAG.getConstant(0, N0.getValueType()), Cond);
- else if (N0.getNode()->hasOneUse()) {
- assert(N0.getOpcode() == ISD::SUB && "Unexpected operation!");
- // (Z-X) == X --> Z == X<<1
- SDValue SH = DAG.getNode(ISD::SHL, dl, N1.getValueType(),
- N1,
+ // Don't do this if X is an immediate that can fold into a cmp
+ // instruction and X+Z has other uses. It could be an induction variable
+ // chain, and the transform would increase register pressure.
+ if (!LegalRHSImm || N0.getNode()->hasOneUse()) {
+ if (N0.getOperand(0) == N1)
+ return DAG.getSetCC(dl, VT, N0.getOperand(1),
+ DAG.getConstant(0, N0.getValueType()), Cond);
+ if (N0.getOperand(1) == N1) {
+ if (DAG.isCommutativeBinOp(N0.getOpcode()))
+ return DAG.getSetCC(dl, VT, N0.getOperand(0),
+ DAG.getConstant(0, N0.getValueType()), Cond);
+ else if (N0.getNode()->hasOneUse()) {
+ assert(N0.getOpcode() == ISD::SUB && "Unexpected operation!");
+ // (Z-X) == X --> Z == X<<1
+ SDValue SH = DAG.getNode(ISD::SHL, dl, N1.getValueType(), N1,
DAG.getConstant(1, getShiftAmountTy(N1.getValueType())));
- if (!DCI.isCalledByLegalizer())
- DCI.AddToWorklist(SH.getNode());
- return DAG.getSetCC(dl, VT, N0.getOperand(0), SH, Cond);
+ if (!DCI.isCalledByLegalizer())
+ DCI.AddToWorklist(SH.getNode());
+ return DAG.getSetCC(dl, VT, N0.getOperand(0), SH, Cond);
+ }
}
}
}