[PATCH] D98697: [IndVars] Provide eliminateIVComparison with context

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev updated this revision to Diff 331533.
mkazantsev added a comment.

Rebased on top of new API for predicate evaluation. Now the order of checks should be from cheap to expensive. Hope this is more CT-friendly.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D98697/new/

https://reviews.llvm.org/D98697

Files:
  llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
  llvm/test/Transforms/IndVarSimplify/checks_against_min_value.ll
  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
@@ -951,11 +951,9 @@
 ; CHECK-NEXT:    [[C1:%.*]] = icmp ne i32 [[IV]], 0
 ; CHECK-NEXT:    br i1 [[C1]], label [[CHECKED_1:%.*]], label [[FAIL:%.*]]
 ; CHECK:       checked.1:
-; CHECK-NEXT:    [[C2:%.*]] = icmp ne i32 [[IV]], 0
-; 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:    [[C3:%.*]] = icmp ne i32 [[IV]], 0
-; 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()
@@ -1003,11 +1001,9 @@
 ; CHECK-NEXT:    [[C1:%.*]] = icmp slt i32 [[IV]], 0
 ; CHECK-NEXT:    br i1 [[C1]], label [[CHECKED_1:%.*]], label [[FAIL:%.*]]
 ; CHECK:       checked.1:
-; CHECK-NEXT:    [[C2:%.*]] = icmp slt i32 [[IV]], 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:    [[C3:%.*]] = icmp slt i32 [[IV]], 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/test/Transforms/IndVarSimplify/checks_against_min_value.ll
===================================================================
--- llvm/test/Transforms/IndVarSimplify/checks_against_min_value.ll
+++ llvm/test/Transforms/IndVarSimplify/checks_against_min_value.ll
@@ -15,8 +15,7 @@
 ; CHECK-NEXT:    [[CHECK:%.*]] = icmp slt i32 [[IV_NEXT]], [[IV]]
 ; CHECK-NEXT:    br i1 [[CHECK]], label [[GUARDED]], label [[FAIL:%.*]]
 ; CHECK:       guarded:
-; CHECK-NEXT:    [[LOOP_COND:%.*]] = icmp ne i32 [[IV]], -2147483648
-; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
+; CHECK-NEXT:    br i1 true, label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
 ; CHECK:       exit.loopexit:
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       exit:
@@ -58,8 +57,7 @@
 ; CHECK-NEXT:    [[CHECK:%.*]] = icmp ult i32 [[IV_NEXT]], [[IV]]
 ; CHECK-NEXT:    br i1 [[CHECK]], label [[GUARDED]], label [[FAIL:%.*]]
 ; CHECK:       guarded:
-; CHECK-NEXT:    [[LOOP_COND:%.*]] = icmp ne i32 [[IV]], 0
-; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
+; CHECK-NEXT:    br i1 true, label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
 ; CHECK:       exit.loopexit:
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       exit:
Index: llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
===================================================================
--- llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -261,9 +261,10 @@
   const SCEV *S = SE->getSCEVAtScope(ICmp->getOperand(IVOperIdx), ICmpLoop);
   const SCEV *X = SE->getSCEVAtScope(ICmp->getOperand(1 - IVOperIdx), ICmpLoop);
 
-  // If the condition is always true or always false, replace it with
-  // a constant value.
-  if (auto Ev = SE->evaluatePredicate(Pred, S, X)) {
+  // 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)) {
     ICmp->replaceAllUsesWith(ConstantInt::getBool(ICmp->getContext(), *Ev));
     DeadInsts.emplace_back(ICmp);
     LLVM_DEBUG(dbgs() << "INDVARS: Eliminated comparison: " << *ICmp << '\n');


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