This test case:
long test(long x) { return (x & 123124) | 3; }
Currently compiles to:
_test:
orl $3, %edi
movq %rdi, %rax
andq $123127, %rax
ret
This is because instruction and DAG combiners canonicalize
(or (and x, C), D) -> (and (or, D), (C | D))
However, this is only profitable if (C & D) != 0. It gets in the way of the
3-addressification because the input bits are known to be zero.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97616 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 8ba0669..5cd70c9 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1786,7 +1786,7 @@
SDValue RAND = ReassociateOps(ISD::AND, N->getDebugLoc(), N0, N1);
if (RAND.getNode() != 0)
return RAND;
- // fold (and (or x, 0xFFFF), 0xFF) -> 0xFF
+ // fold (and (or x, C), D) -> D if (C & D) == D
if (N1C && N0.getOpcode() == ISD::OR)
if (ConstantSDNode *ORI = dyn_cast<ConstantSDNode>(N0.getOperand(1)))
if ((ORI->getAPIntValue() & N1C->getAPIntValue()) == N1C->getAPIntValue())
@@ -2025,13 +2025,15 @@
if (ROR.getNode() != 0)
return ROR;
// Canonicalize (or (and X, c1), c2) -> (and (or X, c2), c1|c2)
+ // iff (c1 & c2) == 0.
if (N1C && N0.getOpcode() == ISD::AND && N0.getNode()->hasOneUse() &&
isa<ConstantSDNode>(N0.getOperand(1))) {
ConstantSDNode *C1 = cast<ConstantSDNode>(N0.getOperand(1));
- return DAG.getNode(ISD::AND, N->getDebugLoc(), VT,
- DAG.getNode(ISD::OR, N0.getDebugLoc(), VT,
- N0.getOperand(0), N1),
- DAG.FoldConstantArithmetic(ISD::OR, VT, N1C, C1));
+ if ((C1->getZExtValue() & N1C->getZExtValue()) != 0)
+ return DAG.getNode(ISD::AND, N->getDebugLoc(), VT,
+ DAG.getNode(ISD::OR, N0.getDebugLoc(), VT,
+ N0.getOperand(0), N1),
+ DAG.FoldConstantArithmetic(ISD::OR, VT, N1C, C1));
}
// fold (or (setcc x), (setcc y)) -> (setcc (or x, y))
if (isSetCCEquivalent(N0, LL, LR, CC0) && isSetCCEquivalent(N1, RL, RR, CC1)){