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[SelectionDAG] Add the option of disabling generic combines. 

Summary:
For some targets generic combines don't really do much and they
consume a disproportionate amount of time.
There's not really a mechanism in SDISel to tactically disable
combines, but we can have a switch to disable all of them and
let the targets just implement what they specifically need.

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D79112
This commit is contained in:
Marcello Maggioni 2020-04-29 01:25:58 +00:00
parent 0c148430cf
commit dbaed589ab
2 changed files with 14 additions and 5 deletions
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5
llvm/include/llvm/CodeGen/SelectionDAGTargetInfo.h
View File

@ -160,6 +160,11 @@ public:
virtual bool generateFMAsInMachineCombiner(CodeGenOpt::Level OptLevel) const { virtual bool generateFMAsInMachineCombiner(CodeGenOpt::Level OptLevel) const {
return false; return false;
} }
// Return true if the DAG Combiner should disable generic combines.
virtual bool disableGenericCombines(CodeGenOpt::Level OptLevel) const {
return false;
}
}; };
} // end namespace llvm } // end namespace llvm

14
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -130,12 +130,14 @@ namespace {
class DAGCombiner { class DAGCombiner {
SelectionDAG &DAG; SelectionDAG &DAG;
const TargetLowering &TLI; const TargetLowering &TLI;
const SelectionDAGTargetInfo *STI;
CombineLevel Level; CombineLevel Level;
CodeGenOpt::Level OptLevel; CodeGenOpt::Level OptLevel;
bool LegalDAG = false; bool LegalDAG = false;
bool LegalOperations = false; bool LegalOperations = false;
bool LegalTypes = false; bool LegalTypes = false;
bool ForCodeSize; bool ForCodeSize;
bool DisableGenericCombines;
/// Worklist of all of the nodes that need to be simplified. /// Worklist of all of the nodes that need to be simplified.
/// ///
@ -223,9 +225,11 @@ namespace {
public: public:
DAGCombiner(SelectionDAG &D, AliasAnalysis *AA, CodeGenOpt::Level OL) DAGCombiner(SelectionDAG &D, AliasAnalysis *AA, CodeGenOpt::Level OL)
: DAG(D), TLI(D.getTargetLoweringInfo()), Level(BeforeLegalizeTypes), : DAG(D), TLI(D.getTargetLoweringInfo()),
OptLevel(OL), AA(AA) { STI(D.getSubtarget().getSelectionDAGInfo()),
Level(BeforeLegalizeTypes), OptLevel(OL), AA(AA) {
ForCodeSize = DAG.shouldOptForSize(); ForCodeSize = DAG.shouldOptForSize();
DisableGenericCombines = STI && STI->disableGenericCombines(OptLevel);
MaximumLegalStoreInBits = 0; MaximumLegalStoreInBits = 0;
// We use the minimum store size here, since that's all we can guarantee // We use the minimum store size here, since that's all we can guarantee
@ -1648,7 +1652,9 @@ SDValue DAGCombiner::visit(SDNode *N) {
} }
SDValue DAGCombiner::combine(SDNode *N) { SDValue DAGCombiner::combine(SDNode *N) {
SDValue RV = visit(N); SDValue RV;
if (!DisableGenericCombines)
RV = visit(N);
// If nothing happened, try a target-specific DAG combine. // If nothing happened, try a target-specific DAG combine.
if (!RV.getNode()) { if (!RV.getNode()) {
@ -11790,7 +11796,6 @@ SDValue DAGCombiner::visitFADDForFMACombine(SDNode *N) {
if (!AllowFusionGlobally && !isContractable(N)) if (!AllowFusionGlobally && !isContractable(N))
return SDValue(); return SDValue();
const SelectionDAGTargetInfo *STI = DAG.getSubtarget().getSelectionDAGInfo();
if (STI && STI->generateFMAsInMachineCombiner(OptLevel)) if (STI && STI->generateFMAsInMachineCombiner(OptLevel))
return SDValue(); return SDValue();
@ -12008,7 +12013,6 @@ SDValue DAGCombiner::visitFSUBForFMACombine(SDNode *N) {
if (!AllowFusionGlobally && !isContractable(N)) if (!AllowFusionGlobally && !isContractable(N))
return SDValue(); return SDValue();
const SelectionDAGTargetInfo *STI = DAG.getSubtarget().getSelectionDAGInfo();
if (STI && STI->generateFMAsInMachineCombiner(OptLevel)) if (STI && STI->generateFMAsInMachineCombiner(OptLevel))
return SDValue(); return SDValue();