Enable splitting indexing from loads with TargetConstants
When I recommitted r208640 (in r216898) I added an exclusion for TargetConstant
offsets, as there is no guarantee that a backend can handle them on generic
ADDs (even if it generates them during address-mode matching) -- and,
specifically, applying this transformation directly with TargetConstants caused
a self-hosting failure on PPC64. Ignoring all TargetConstants, however, is less
than ideal. Instead, for non-opaque constants, we can convert them into regular
constants for use with the generated ADD (or SUB).
llvm-svn: 216908
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 92ee5c9..1186683 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -8029,8 +8029,19 @@
assert(AM != ISD::UNINDEXED);
SDValue BP = LD->getOperand(1);
SDValue Inc = LD->getOperand(2);
- assert(Inc.getOpcode() != ISD::TargetConstant &&
- "Cannot split out indexing using target constants");
+
+ // Some backends use TargetConstants for load offsets, but don't expect
+ // TargetConstants in general ADD nodes. We can convert these constants into
+ // regular Constants (if the constant is not opaque).
+ assert((Inc.getOpcode() != ISD::TargetConstant ||
+ !cast<ConstantSDNode>(Inc)->isOpaque()) &&
+ "Cannot split out indexing using opaque target constants");
+ if (Inc.getOpcode() == ISD::TargetConstant) {
+ ConstantSDNode *ConstInc = cast<ConstantSDNode>(Inc);
+ Inc = DAG.getConstant(*ConstInc->getConstantIntValue(),
+ ConstInc->getValueType(0));
+ }
+
unsigned Opc =
(AM == ISD::PRE_INC || AM == ISD::POST_INC ? ISD::ADD : ISD::SUB);
return DAG.getNode(Opc, SDLoc(LD), BP.getSimpleValueType(), BP, Inc);
@@ -8071,16 +8082,18 @@
// Indexed loads.
assert(N->getValueType(2) == MVT::Other && "Malformed indexed loads?");
- // If this load has an TargetConstant offset, then we cannot split the
- // indexing into an add/sub directly (that TargetConstant may not be
- // valid for a different type of node).
- bool HasTCInc = LD->getOperand(2).getOpcode() == ISD::TargetConstant;
+ // If this load has an opaque TargetConstant offset, then we cannot split
+ // the indexing into an add/sub directly (that TargetConstant may not be
+ // valid for a different type of node, and we cannot convert an opaque
+ // target constant into a regular constant).
+ bool HasOTCInc = LD->getOperand(2).getOpcode() == ISD::TargetConstant &&
+ cast<ConstantSDNode>(LD->getOperand(2))->isOpaque();
if (!N->hasAnyUseOfValue(0) &&
- ((MaySplitLoadIndex && !HasTCInc) || !N->hasAnyUseOfValue(1))) {
+ ((MaySplitLoadIndex && !HasOTCInc) || !N->hasAnyUseOfValue(1))) {
SDValue Undef = DAG.getUNDEF(N->getValueType(0));
SDValue Index;
- if (N->hasAnyUseOfValue(1) && MaySplitLoadIndex && !HasTCInc) {
+ if (N->hasAnyUseOfValue(1) && MaySplitLoadIndex && !HasOTCInc) {
Index = SplitIndexingFromLoad(LD);
// Try to fold the base pointer arithmetic into subsequent loads and
// stores.