[llvm] f33118c - [IndVars] Support different types of ExitCount when optimizing exit conds

[Max Kazantsev via llvm-commits]

Author: Max Kazantsev
Date: 2020-11-18T18:20:05+07:00
New Revision: f33118c61ce051f13515f5c9b862302fc4fdb89e

URL: https://github.com/llvm/llvm-project/commit/f33118c61ce051f13515f5c9b862302fc4fdb89e
DIFF: https://github.com/llvm/llvm-project/commit/f33118c61ce051f13515f5c9b862302fc4fdb89e.diff

LOG: [IndVars] Support different types of ExitCount when optimizing exit conds

In some cases we can handle IV and iter count of different types. It's a typical situation
after IV have been widened. This patch adds support for such cases, when legal.

Differential Revision: https://reviews.llvm.org/D88528
Reviewed By: skatkov

Added: 
    

Modified: 
    llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
    llvm/test/Transforms/IndVarSimplify/predicated_ranges.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
index e36d2e7f3a5b..d9a959d2fb6d 100644
--- a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -1360,6 +1360,18 @@ static bool optimizeLoopExitWithUnknownExitCount(
   if (Inverted)
     return false;
 
+  auto *ARTy = LHSS->getType();
+  auto *MaxIterTy = MaxIter->getType();
+  // If possible, adjust types.
+  if (SE->getTypeSizeInBits(ARTy) > SE->getTypeSizeInBits(MaxIterTy))
+    MaxIter = SE->getZeroExtendExpr(MaxIter, ARTy);
+  else if (SE->getTypeSizeInBits(ARTy) < SE->getTypeSizeInBits(MaxIterTy)) {
+    const SCEV *MinusOne = SE->getMinusOne(ARTy);
+    auto *MaxAllowedIter = SE->getZeroExtendExpr(MinusOne, MaxIterTy);
+    if (SE->isKnownPredicateAt(ICmpInst::ICMP_ULE, MaxIter, MaxAllowedIter, BI))
+      MaxIter = SE->getTruncateExpr(MaxIter, ARTy);
+  }
+
   if (SkipLastIter) {
     const SCEV *One = SE->getOne(MaxIter->getType());
     MaxIter = SE->getMinusSCEV(MaxIter, One);

diff  --git a/llvm/test/Transforms/IndVarSimplify/predicated_ranges.ll b/llvm/test/Transforms/IndVarSimplify/predicated_ranges.ll
index 27b16027664d..85946bbe59e6 100644
--- a/llvm/test/Transforms/IndVarSimplify/predicated_ranges.ll
+++ b/llvm/test/Transforms/IndVarSimplify/predicated_ranges.ll
@@ -624,6 +624,7 @@ define void @test_can_predicate_trunc_unsigned(i32* %p, i32* %arr) {
 ; CHECK-NEXT:  preheader:
 ; CHECK-NEXT:    [[LEN:%.*]] = load i32, i32* [[P:%.*]], align 4
 ; CHECK-NEXT:    [[START:%.*]] = zext i32 [[LEN]] to i64
+; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[LEN]], -1
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ [[START]], [[PREHEADER:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
@@ -631,9 +632,8 @@ define void @test_can_predicate_trunc_unsigned(i32* %p, i32* %arr) {
 ; CHECK-NEXT:    br i1 [[ZERO_COND]], label [[EXIT:%.*]], label [[RANGE_CHECK_BLOCK:%.*]]
 ; CHECK:       range_check_block:
 ; CHECK-NEXT:    [[IV_NEXT]] = sub nsw i64 [[IV]], 1
-; CHECK-NEXT:    [[NARROW:%.*]] = trunc i64 [[IV_NEXT]] to i32
-; CHECK-NEXT:    [[RANGE_CHECK:%.*]] = icmp ult i32 [[NARROW]], [[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* [[ARR:%.*]], i64 [[IV]]
 ; CHECK-NEXT:    [[EL:%.*]] = load i32, i32* [[EL_PTR]], align 4
@@ -678,6 +678,7 @@ define void @test_can_predicate_trunc_unsigned_inverted(i32* %p, i32* %arr) {
 ; CHECK-NEXT:  preheader:
 ; CHECK-NEXT:    [[LEN:%.*]] = load i32, i32* [[P:%.*]], align 4
 ; CHECK-NEXT:    [[START:%.*]] = zext i32 [[LEN]] to i64
+; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[LEN]], -1
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ [[START]], [[PREHEADER:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
@@ -685,9 +686,8 @@ define void @test_can_predicate_trunc_unsigned_inverted(i32* %p, i32* %arr) {
 ; CHECK-NEXT:    br i1 [[ZERO_COND]], label [[EXIT:%.*]], label [[RANGE_CHECK_BLOCK:%.*]]
 ; CHECK:       range_check_block:
 ; CHECK-NEXT:    [[IV_NEXT]] = sub nsw i64 [[IV]], 1
-; CHECK-NEXT:    [[NARROW:%.*]] = trunc i64 [[IV_NEXT]] to i32
-; CHECK-NEXT:    [[RANGE_CHECK:%.*]] = icmp uge i32 [[NARROW]], [[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* [[ARR:%.*]], i64 [[IV]]
 ; CHECK-NEXT:    [[EL:%.*]] = load i32, i32* [[EL_PTR]], align 4