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CodeGen: don't form illegail EXTLOAD operations.

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It turns out that in most cases (the main exception being i1-related
types) once these operations are formed we cannot separate them and
the targets end up having to deal with them whether they want to or
not.

This is not a good situation, and a more reasonable default can be
formed by ackowledging this and having targets leave them as Legal.
Only x86 seems to be affected (other targets don't even try marking
the operation Expand).

Mostly there's no visible change here yet, but it will be useful to
have truly expanded EXTLOADS for MVT::f16 softening support.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213162 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tim Northover 2014-07-16 15:37:24 +00:00
parent 80221b9682
commit 1cafa00e26
2 changed files with 8 additions and 5 deletions
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6
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -5530,8 +5530,7 @@ SDValue DAGCombiner::visitANY_EXTEND(SDNode *N) {
// scalars.
if (ISD::isNON_EXTLoad(N0.getNode()) && !VT.isVector() &&
ISD::isUNINDEXEDLoad(N0.getNode()) &&
((!LegalOperations && !cast<LoadSDNode>(N0)->isVolatile()) ||
TLI.isLoadExtLegal(ISD::EXTLOAD, N0.getValueType()))) {
TLI.isLoadExtLegal(ISD::EXTLOAD, N0.getValueType())) {
bool DoXform = true;
SmallVector<SDNode*, 4> SetCCs;
if (!N0.hasOneUse())
@ -7228,8 +7227,7 @@ SDValue DAGCombiner::visitFP_EXTEND(SDNode *N) {
// fold (fpext (load x)) -> (fpext (fptrunc (extload x)))
if (ISD::isNormalLoad(N0.getNode()) && N0.hasOneUse() &&
((!LegalOperations && !cast<LoadSDNode>(N0)->isVolatile()) ||
TLI.isLoadExtLegal(ISD::EXTLOAD, N0.getValueType()))) {
TLI.isLoadExtLegal(ISD::EXTLOAD, N0.getValueType())) {
LoadSDNode *LN0 = cast<LoadSDNode>(N0);
SDValue ExtLoad = DAG.getExtLoad(ISD::EXTLOAD, SDLoc(N), VT,
LN0->getChain(),

7
lib/Target/X86/X86ISelLowering.cpp
View File

@ -878,7 +878,12 @@ void X86TargetLowering::resetOperationActions() {
(MVT::SimpleValueType)InnerVT, Expand);
setLoadExtAction(ISD::SEXTLOAD, VT, Expand);
setLoadExtAction(ISD::ZEXTLOAD, VT, Expand);
setLoadExtAction(ISD::EXTLOAD, VT, Expand);
// N.b. ISD::EXTLOAD legality is basically ignored except for i1-like types,
// we have to deal with them whether we ask for Expansion or not. Setting
// Expand causes its own optimisation problems though, so leave them legal.
if (VT.getVectorElementType() == MVT::i1)
setLoadExtAction(ISD::EXTLOAD, VT, Expand);
}
// FIXME: In order to prevent SSE instructions being expanded to MMX ones