Fix DAGCombiner to avoid going into an infinite loop when it
encounters (and:i64 (shl:i64 (load:i64), 1), 0xffffffff).
This fixes rdar://8606584.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118143 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 602d5bf..10aa36c 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3667,6 +3667,20 @@
// fold (zext (truncate x)) -> (and x, mask)
if (N0.getOpcode() == ISD::TRUNCATE &&
(!LegalOperations || TLI.isOperationLegal(ISD::AND, VT))) {
+
+ // fold (zext (truncate (load x))) -> (zext (smaller load x))
+ // fold (zext (truncate (srl (load x), c))) -> (zext (smaller load (x+c/n)))
+ SDValue NarrowLoad = ReduceLoadWidth(N0.getNode());
+ if (NarrowLoad.getNode()) {
+ SDNode* oye = N0.getNode()->getOperand(0).getNode();
+ if (NarrowLoad.getNode() != N0.getNode()) {
+ CombineTo(N0.getNode(), NarrowLoad);
+ // CombineTo deleted the truncate, if needed, but not what's under it.
+ AddToWorkList(oye);
+ }
+ return SDValue(N, 0); // Return N so it doesn't get rechecked!
+ }
+
SDValue Op = N0.getOperand(0);
if (Op.getValueType().bitsLT(VT)) {
Op = DAG.getNode(ISD::ANY_EXTEND, N->getDebugLoc(), VT, Op);
@@ -4102,6 +4116,17 @@
}
}
+ // If the load is shifted left (and the result isn't shifted back right),
+ // we can fold the truncate through the shift.
+ unsigned ShLeftAmt = 0;
+ if (ShAmt == 0 && N0.getOpcode() == ISD::SHL && N0.hasOneUse() &&
+ TLI.isNarrowingProfitable(N0.getValueType(), VT)) {
+ if (ConstantSDNode *N01 = dyn_cast<ConstantSDNode>(N0.getOperand(1))) {
+ ShLeftAmt = N01->getZExtValue();
+ N0 = N0.getOperand(0);
+ }
+ }
+
// Do not generate loads of non-round integer types since these can
// be expensive (and would be wrong if the type is not byte sized).
if (isa<LoadSDNode>(N0) && N0.hasOneUse() && ExtVT.isRound() &&
@@ -4140,8 +4165,18 @@
DAG.ReplaceAllUsesOfValueWith(N0.getValue(1), Load.getValue(1),
&DeadNodes);
+ // Shift the result left, if we've swallowed a left shift.
+ SDValue Result = Load;
+ if (ShLeftAmt != 0) {
+ EVT ShImmTy = getShiftAmountTy();
+ if (!isUIntN(ShImmTy.getSizeInBits(), ShLeftAmt))
+ ShImmTy = VT;
+ Result = DAG.getNode(ISD::SHL, N0.getDebugLoc(), VT,
+ Result, DAG.getConstant(ShLeftAmt, ShImmTy));
+ }
+
// Return the new loaded value.
- return Load;
+ return Result;
}
return SDValue();