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[DFAJumpThreading] Early exit if switch is not in a loop #85360

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merged 1 commit into from
Mar 15, 2024
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[DFAJumpThreading] Early exit if switch is not in a loop #85360

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19 changes: 14 additions & 5 deletions llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,7 @@
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/CodeMetrics.h"
#include "llvm/Analysis/DomTreeUpdater.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/CFG.h"
Expand Down Expand Up @@ -131,9 +132,9 @@ void unfold(DomTreeUpdater *DTU, SelectInstToUnfold SIToUnfold,

class DFAJumpThreading {
public:
DFAJumpThreading(AssumptionCache *AC, DominatorTree *DT,
DFAJumpThreading(AssumptionCache *AC, DominatorTree *DT, LoopInfo *LI,
TargetTransformInfo *TTI, OptimizationRemarkEmitter *ORE)
: AC(AC), DT(DT), TTI(TTI), ORE(ORE) {}
: AC(AC), DT(DT), LI(LI), TTI(TTI), ORE(ORE) {}

bool run(Function &F);

Expand Down Expand Up @@ -161,6 +162,7 @@ class DFAJumpThreading {

AssumptionCache *AC;
DominatorTree *DT;
LoopInfo *LI;
TargetTransformInfo *TTI;
OptimizationRemarkEmitter *ORE;
};
Expand Down Expand Up @@ -378,7 +380,8 @@ inline raw_ostream &operator<<(raw_ostream &OS, const ThreadingPath &TPath) {
#endif

struct MainSwitch {
MainSwitch(SwitchInst *SI, OptimizationRemarkEmitter *ORE) {
MainSwitch(SwitchInst *SI, LoopInfo *LI, OptimizationRemarkEmitter *ORE)
: LI(LI) {
if (isCandidate(SI)) {
Instr = SI;
} else {
Expand Down Expand Up @@ -411,6 +414,10 @@ struct MainSwitch {
if (!isa<PHINode>(SICond))
return false;

// The switch must be in a loop.
if (!LI->getLoopFor(SI->getParent()))
return false;

addToQueue(SICond, Q, SeenValues);

while (!Q.empty()) {
Expand Down Expand Up @@ -488,6 +495,7 @@ struct MainSwitch {
return true;
}

LoopInfo *LI;
SwitchInst *Instr = nullptr;
SmallVector<SelectInstToUnfold, 4> SelectInsts;
};
Expand Down Expand Up @@ -1262,7 +1270,7 @@ bool DFAJumpThreading::run(Function &F) {

LLVM_DEBUG(dbgs() << "\nCheck if SwitchInst in BB " << BB.getName()
<< " is a candidate\n");
MainSwitch Switch(SI, ORE);
MainSwitch Switch(SI, LI, ORE);

if (!Switch.getInstr())
continue;
Expand Down Expand Up @@ -1315,10 +1323,11 @@ PreservedAnalyses DFAJumpThreadingPass::run(Function &F,
FunctionAnalysisManager &AM) {
AssumptionCache &AC = AM.getResult<AssumptionAnalysis>(F);
DominatorTree &DT = AM.getResult<DominatorTreeAnalysis>(F);
LoopInfo &LI = AM.getResult<LoopAnalysis>(F);
TargetTransformInfo &TTI = AM.getResult<TargetIRAnalysis>(F);
OptimizationRemarkEmitter ORE(&F);

if (!DFAJumpThreading(&AC, &DT, &TTI, &ORE).run(F))
if (!DFAJumpThreading(&AC, &DT, &LI, &TTI, &ORE).run(F))
return PreservedAnalyses::all();

PreservedAnalyses PA;
Expand Down