[IndVars] Use isLoopBackedgeGuardedByCond for last iteration check

Use more context to prove contextual facts about the last iteration. It is
only executed when the backedge is taken, so we can use `isLoopBackedgeGuardedByCond`
to make this check.

Differential Revision: https://reviews.llvm.org/D91535
Reviewed By: skatkov

diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 5a7f1b94a4e87f60d54c422adb449702aef86d5a..53fd668be05cdae324443e57f72d6049e1f5f50a 100644 (file)
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -9673,7 +9673,7 @@ ScalarEvolution::getLoopInvariantExitCondDuringFirstIterations(
   // Value of IV on suggested last iteration.
   const SCEV *Last = AR->evaluateAtIteration(MaxIter, *this);
   // Does it still meet the requirement?
-  if (!isKnownPredicateAt(Pred, Last, RHS, Context))
+  if (!isLoopBackedgeGuardedByCond(L, Pred, Last, RHS))
     return None;
   // Because step is +/- 1 and MaxIter has same type as Start (i.e. it does
   // not exceed max unsigned value of this type), this effectively proves

diff --git a/llvm/test/Transforms/IndVarSimplify/predicated_ranges.ll b/llvm/test/Transforms/IndVarSimplify/predicated_ranges.ll
index 85946bbe59e6468280ecc96f14d8206821a851b9..ffe4db9435488935975bf2588a087fb475ca8988 100644 (file)
--- a/llvm/test/Transforms/IndVarSimplify/predicated_ranges.ll
+++ b/llvm/test/Transforms/IndVarSimplify/predicated_ranges.ll
@@ -835,15 +835,16 @@ define void @test_can_predicate_simple_unsigned_different_start(i32 %start, i32*
 ; CHECK-LABEL: @test_can_predicate_simple_unsigned_different_start(
 ; CHECK-NEXT:  preheader:
 ; CHECK-NEXT:    [[LEN:%.*]] = load i32, i32* [[P:%.*]], align 4
+; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[START:%.*]], -1
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
-; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START:%.*]], [[PREHEADER:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
+; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START]], [[PREHEADER:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
 ; CHECK-NEXT:    [[ZERO_COND:%.*]] = icmp eq i32 [[IV]], 0
 ; CHECK-NEXT:    br i1 [[ZERO_COND]], label [[EXIT:%.*]], label [[RANGE_CHECK_BLOCK:%.*]]
 ; CHECK:       range_check_block:
 ; CHECK-NEXT:    [[IV_NEXT]] = sub i32 [[IV]], 1
-; CHECK-NEXT:    [[RANGE_CHECK:%.*]] = icmp ult i32 [[IV_NEXT]], [[LEN]]
-; CHECK-NEXT:    br i1 [[RANGE_CHECK]], label [[BACKEDGE]], label [[FAIL:%.*]]
+; CHECK-NEXT:    [[RANGE_CHECK1:%.*]] = icmp ult i32 [[TMP0]], [[LEN]]
+; CHECK-NEXT:    br i1 [[RANGE_CHECK1]], label [[BACKEDGE]], label [[FAIL:%.*]]
 ; CHECK:       backedge:
 ; CHECK-NEXT:    [[EL_PTR:%.*]] = getelementptr i32, i32* [[P]], i32 [[IV]]
 ; CHECK-NEXT:    [[EL:%.*]] = load i32, i32* [[EL_PTR]], align 4
@@ -885,15 +886,16 @@ define void @test_can_predicate_simple_unsigned_inverted_different_start(i32 %st
 ; CHECK-LABEL: @test_can_predicate_simple_unsigned_inverted_different_start(
 ; CHECK-NEXT:  preheader:
 ; CHECK-NEXT:    [[LEN:%.*]] = load i32, i32* [[P:%.*]], align 4
+; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[START:%.*]], -1
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
-; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START:%.*]], [[PREHEADER:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
+; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START]], [[PREHEADER:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
 ; CHECK-NEXT:    [[ZERO_COND:%.*]] = icmp eq i32 [[IV]], 0
 ; CHECK-NEXT:    br i1 [[ZERO_COND]], label [[EXIT:%.*]], label [[RANGE_CHECK_BLOCK:%.*]]
 ; CHECK:       range_check_block:
 ; CHECK-NEXT:    [[IV_NEXT]] = sub i32 [[IV]], 1
-; CHECK-NEXT:    [[RANGE_CHECK:%.*]] = icmp uge i32 [[IV_NEXT]], [[LEN]]
-; CHECK-NEXT:    br i1 [[RANGE_CHECK]], label [[FAIL:%.*]], label [[BACKEDGE]]
+; CHECK-NEXT:    [[RANGE_CHECK1:%.*]] = icmp uge i32 [[TMP0]], [[LEN]]
+; CHECK-NEXT:    br i1 [[RANGE_CHECK1]], label [[FAIL:%.*]], label [[BACKEDGE]]
 ; CHECK:       backedge:
 ; CHECK-NEXT:    [[EL_PTR:%.*]] = getelementptr i32, i32* [[P]], i32 [[IV]]
 ; CHECK-NEXT:    [[EL:%.*]] = load i32, i32* [[EL_PTR]], align 4