[PATCH] D98924: [IndVars] Sharpen context in eliminateIVComparison

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev updated this revision to Diff 331789.
mkazantsev added a comment.

clang-format


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D98924/new/

https://reviews.llvm.org/D98924

Files:
  llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
  llvm/test/Transforms/IndVarSimplify/eliminate-comparison.ll


Index: llvm/test/Transforms/IndVarSimplify/eliminate-comparison.ll
===================================================================
--- llvm/test/Transforms/IndVarSimplify/eliminate-comparison.ll
+++ llvm/test/Transforms/IndVarSimplify/eliminate-comparison.ll
@@ -1101,13 +1101,11 @@
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
 ; CHECK-NEXT:    [[C1:%.*]] = icmp ne i32 [[IV]], 0
-; CHECK-NEXT:    [[C2:%.*]] = icmp ne i32 [[IV]], 0
-; CHECK-NEXT:    [[C3:%.*]] = icmp ne i32 [[IV]], 0
 ; CHECK-NEXT:    br i1 [[C1]], label [[CHECKED_1:%.*]], label [[FAIL:%.*]]
 ; CHECK:       checked.1:
-; CHECK-NEXT:    br i1 [[C2]], label [[CHECKED_2:%.*]], label [[FAIL]]
+; CHECK-NEXT:    br i1 true, label [[CHECKED_2:%.*]], label [[FAIL]]
 ; CHECK:       checked.2:
-; CHECK-NEXT:    br i1 [[C3]], label [[BACKEDGE]], label [[FAIL]]
+; CHECK-NEXT:    br i1 true, label [[BACKEDGE]], label [[FAIL]]
 ; CHECK:       backedge:
 ; CHECK-NEXT:    [[IV_NEXT]] = add i32 [[IV]], 758394
 ; CHECK-NEXT:    [[LOOP_COND:%.*]] = call i1 @cond_func()
Index: llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
===================================================================
--- llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -281,8 +281,11 @@
 
   // If the condition is always true or always false in the given context,
   // replace it with a constant value.
-  // TODO: We can sharpen the context to common dominator of all ICmp's users.
-  if (auto Ev = SE->evaluatePredicateAt(Pred, S, X, ICmp)) {
+  SmallVector<Instruction *, 4> Users;
+  for (auto *U : ICmp->users())
+    Users.push_back(cast<Instruction>(U));
+  const Instruction *CtxI = findCommonDominator(Users, *DT);
+  if (auto Ev = SE->evaluatePredicateAt(Pred, S, X, CtxI)) {
     ICmp->replaceAllUsesWith(ConstantInt::getBool(ICmp->getContext(), *Ev));
     DeadInsts.emplace_back(ICmp);
     LLVM_DEBUG(dbgs() << "INDVARS: Eliminated comparison: " << *ICmp << '\n');


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