[CodeGen] Compute DT/LI lazily in SafeStackLegacyPass. NFC.
We currently require SCEV, which requires DT/LI. Those are expensive to
compute, but the pass only runs for functions that have the safestack
attribute.
Compute DT/LI to build SCEV lazily, only when the pass is actually going
to transform the function.
Differential Revision: https://reviews.llvm.org/D31302
llvm-svn: 302610
diff --git a/llvm/lib/CodeGen/SafeStack.cpp b/llvm/lib/CodeGen/SafeStack.cpp
index f0663eb..08b3d34 100644
--- a/llvm/lib/CodeGen/SafeStack.cpp
+++ b/llvm/lib/CodeGen/SafeStack.cpp
@@ -774,7 +774,8 @@
SafeStackLegacyPass() : SafeStackLegacyPass(nullptr) {}
void getAnalysisUsage(AnalysisUsage &AU) const override {
- AU.addRequired<ScalarEvolutionWrapperPass>();
+ AU.addRequired<TargetLibraryInfoWrapperPass>();
+ AU.addRequired<AssumptionCacheTracker>();
}
bool runOnFunction(Function &F) override {
@@ -799,7 +800,19 @@
report_fatal_error("TargetLowering instance is required");
auto *DL = &F.getParent()->getDataLayout();
- auto &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
+ auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
+ auto &ACT = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
+
+ // Compute DT and LI only for functions that have the attribute.
+ // This is only useful because the legacy pass manager doesn't let us
+ // compute analyzes lazily.
+ // In the backend pipeline, nothing preserves DT before SafeStack, so we
+ // would otherwise always compute it wastefully, even if there is no
+ // function with the safestack attribute.
+ DominatorTree DT(F);
+ LoopInfo LI(DT);
+
+ ScalarEvolution SE(F, TLI, ACT, DT, LI);
return SafeStack(F, *TL, *DL, SE).run();
}