add two dag combines:
(C1-X) == C2 --> X == C1-C2
(X+C1) == C2 --> X == C2-C1
This allows us to compile this:
bool %X(int %X) {
%Y = add int %X, 14
%Z = setne int %Y, 12345
ret bool %Z
}
into this:
_X:
cmpl $12331, 4(%esp)
setne %al
movzbl %al, %eax
andl $1, %eax
ret
not this:
_X:
movl $14, %eax
addl 4(%esp), %eax
cmpl $12345, %eax
setne %al
movzbl %al, %eax
andl $1, %eax
ret
Testcase here: Regression/CodeGen/X86/compare-add.ll
nukage of the and coming up next.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@25898 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 6fd1fe4..d57400b 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2623,19 +2623,36 @@
return DAG.getSetCC(VT, N0.getOperand(0), N1.getOperand(1), Cond);
}
}
-
- // Turn (X^C1) == C2 into X == C1^C2 iff X&~C1 = 0. Common for condcodes.
- if (N0.getOpcode() == ISD::XOR)
- if (ConstantSDNode *XORC = dyn_cast<ConstantSDNode>(N0.getOperand(1)))
- if (ConstantSDNode *RHSC = dyn_cast<ConstantSDNode>(N1)) {
+
+ if (ConstantSDNode *RHSC = dyn_cast<ConstantSDNode>(N1)) {
+ if (ConstantSDNode *LHSR = dyn_cast<ConstantSDNode>(N0.getOperand(1))) {
+ // Turn (X+C1) == C2 --> X == C2-C1
+ if (N0.getOpcode() == ISD::ADD && N0.Val->hasOneUse()) {
+ return DAG.getSetCC(VT, N0.getOperand(0),
+ DAG.getConstant(RHSC->getValue()-LHSR->getValue(),
+ N0.getValueType()), Cond);
+ }
+
+ // Turn (X^C1) == C2 into X == C1^C2 iff X&~C1 = 0.
+ if (N0.getOpcode() == ISD::XOR)
// If we know that all of the inverted bits are zero, don't bother
// performing the inversion.
- if (TLI.MaskedValueIsZero(N0.getOperand(0), ~XORC->getValue()))
+ if (TLI.MaskedValueIsZero(N0.getOperand(0), ~LHSR->getValue()))
return DAG.getSetCC(VT, N0.getOperand(0),
- DAG.getConstant(XORC->getValue()^RHSC->getValue(),
+ DAG.getConstant(LHSR->getValue()^RHSC->getValue(),
N0.getValueType()), Cond);
+ }
+
+ // Turn (C1-X) == C2 --> X == C1-C2
+ if (ConstantSDNode *SUBC = dyn_cast<ConstantSDNode>(N0.getOperand(0))) {
+ if (N0.getOpcode() == ISD::SUB && N0.Val->hasOneUse()) {
+ return DAG.getSetCC(VT, N0.getOperand(1),
+ DAG.getConstant(SUBC->getValue()-RHSC->getValue(),
+ N0.getValueType()), Cond);
}
-
+ }
+ }
+
// Simplify (X+Z) == X --> Z == 0
if (N0.getOperand(0) == N1)
return DAG.getSetCC(VT, N0.getOperand(1),