StructurizeCFG: Simplify inserted PHI nodes
Summary:
This improves subsequent divergence analysis in some cases.
Change-Id: I5e95e7ec7fd3fa80d414d1a53a02fea23e3d67d3
Reviewers: arsenm, rampitec
Subscribers: jvesely, wdng, llvm-commits
Differential Revision: https://reviews.llvm.org/D53316
llvm-svn: 344697
diff --git a/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp b/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
index 2bfd992..0db762d 100644
--- a/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
+++ b/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
@@ -13,6 +13,7 @@
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
+#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LegacyDivergenceAnalysis.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/RegionInfo.h"
@@ -596,7 +597,8 @@
/// Add the real PHI value as soon as everything is set up
void StructurizeCFG::setPhiValues() {
- SSAUpdater Updater;
+ SmallVector<PHINode *, 8> InsertedPhis;
+ SSAUpdater Updater(&InsertedPhis);
for (const auto &AddedPhi : AddedPhis) {
BasicBlock *To = AddedPhi.first;
const BBVector &From = AddedPhi.second;
@@ -632,6 +634,26 @@
DeletedPhis.erase(To);
}
assert(DeletedPhis.empty());
+
+ // Simplify any phis inserted by the SSAUpdater if possible
+ bool Changed;
+ do {
+ Changed = false;
+
+ SimplifyQuery Q(Func->getParent()->getDataLayout());
+ Q.DT = DT;
+ for (size_t i = 0; i < InsertedPhis.size(); ++i) {
+ PHINode *Phi = InsertedPhis[i];
+ if (Value *V = SimplifyInstruction(Phi, Q)) {
+ Phi->replaceAllUsesWith(V);
+ Phi->eraseFromParent();
+ InsertedPhis[i] = InsertedPhis.back();
+ InsertedPhis.pop_back();
+ i--;
+ Changed = true;
+ }
+ }
+ } while (Changed);
}
/// Remove phi values from all successors and then remove the terminator.