[llvm-branch-commits] [llvm] bb383ad - [SCEVExp] Fix early exit in ComputeEndCheck. (#156910)
Tobias Hieta via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Tue Sep 9 01:35:38 PDT 2025
Author: Florian Hahn
Date: 2025-09-09T10:36:54+02:00
New Revision: bb383adfafcae15105af39bb5bec07c9245e8784
URL: https://github.com/llvm/llvm-project/commit/bb383adfafcae15105af39bb5bec07c9245e8784
DIFF: https://github.com/llvm/llvm-project/commit/bb383adfafcae15105af39bb5bec07c9245e8784.diff
LOG: [SCEVExp] Fix early exit in ComputeEndCheck. (#156910)
ComputeEndCheck incorrectly returned false for unsigned predicates
starting at zero and a positive step.
The AddRec could still wrap if Step * trunc ExitCount wraps or trunc
ExitCount strips leading 1s.
Fixes https://github.com/llvm/llvm-project/issues/156849.
PR: https://github.com/llvm/llvm-project/pull/156910
(cherry picked from commit f8972c8280d28660aaff888c093a9e01b9ee71e6)
Added:
Modified:
llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
llvm/test/Transforms/LoopDistribute/scev-inserted-runtime-check.ll
llvm/test/Transforms/LoopVectorize/X86/cost-model.ll
llvm/test/Transforms/LoopVectorize/interleaved-accesses-requiring-scev-predicates.ll
llvm/test/Transforms/LoopVectorize/runtime-check-small-clamped-bounds.ll
llvm/test/Transforms/LoopVersioning/wrapping-pointer-versioning.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp b/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
index 24fe08d6c3e4e..bf457194bfd8e 100644
--- a/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
+++ b/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
@@ -2133,8 +2133,15 @@ Value *SCEVExpander::generateOverflowCheck(const SCEVAddRecExpr *AR,
// negative. If Step is known to be positive or negative, only create
// either 1. or 2.
auto ComputeEndCheck = [&]() -> Value * {
- // Checking <u 0 is always false.
- if (!Signed && Start->isZero() && SE.isKnownPositive(Step))
+ // Checking <u 0 is always false, if (Step * trunc ExitCount) does not wrap.
+ // TODO: Predicates that can be proven true/false should be discarded when
+ // the predicates are created, not late during expansion.
+ if (!Signed && Start->isZero() && SE.isKnownPositive(Step) &&
+ DstBits < SrcBits &&
+ ExitCount == SE.getZeroExtendExpr(SE.getTruncateExpr(ExitCount, ARTy),
+ ExitCount->getType()) &&
+ SE.willNotOverflow(Instruction::Mul, Signed, Step,
+ SE.getTruncateExpr(ExitCount, ARTy)))
return ConstantInt::getFalse(Loc->getContext());
// Get the backedge taken count and truncate or extended to the AR type.
diff --git a/llvm/test/Transforms/LoopDistribute/scev-inserted-runtime-check.ll b/llvm/test/Transforms/LoopDistribute/scev-inserted-runtime-check.ll
index 98b89abfeafda..057a60918ecf3 100644
--- a/llvm/test/Transforms/LoopDistribute/scev-inserted-runtime-check.ll
+++ b/llvm/test/Transforms/LoopDistribute/scev-inserted-runtime-check.ll
@@ -10,8 +10,13 @@ define void @f(ptr noalias %a, ptr noalias %b, ptr noalias %c, ptr noalias %d, p
; CHECK-NEXT: br label [[FOR_BODY_LVER_CHECK:%.*]]
; CHECK: for.body.lver.check:
; CHECK-NEXT: [[TMP0:%.*]] = add i64 [[N:%.*]], -1
+; CHECK-NEXT: [[TMP2:%.*]] = trunc i64 [[TMP0]] to i32
+; CHECK-NEXT: [[MUL1:%.*]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 2, i32 [[TMP2]])
+; CHECK-NEXT: [[MUL_RESULT:%.*]] = extractvalue { i32, i1 } [[MUL1]], 0
+; CHECK-NEXT: [[MUL_OVERFLOW:%.*]] = extractvalue { i32, i1 } [[MUL1]], 1
; CHECK-NEXT: [[TMP1:%.*]] = icmp ugt i64 [[TMP0]], 4294967295
-; CHECK-NEXT: br i1 [[TMP1]], label [[FOR_BODY_PH_LVER_ORIG:%.*]], label [[FOR_BODY_PH_LDIST1:%.*]]
+; CHECK-NEXT: [[TMP3:%.*]] = or i1 [[MUL_OVERFLOW]], [[TMP1]]
+; CHECK-NEXT: br i1 [[TMP3]], label [[FOR_BODY_PH_LVER_ORIG:%.*]], label [[FOR_BODY_PH_LDIST1:%.*]]
; CHECK: for.body.ph.lver.orig:
; CHECK-NEXT: br label [[FOR_BODY_LVER_ORIG:%.*]]
; CHECK: for.body.lver.orig:
@@ -75,7 +80,7 @@ define void @f(ptr noalias %a, ptr noalias %b, ptr noalias %c, ptr noalias %d, p
; CHECK-NEXT: br i1 [[EXITCOND]], label [[FOR_END_LOOPEXIT2:%.*]], label [[FOR_BODY]]
; CHECK: for.end.loopexit:
; CHECK-NEXT: br label [[FOR_END:%.*]]
-; CHECK: for.end.loopexit1:
+; CHECK: for.end.loopexit2:
; CHECK-NEXT: br label [[FOR_END]]
; CHECK: for.end:
; CHECK-NEXT: ret void
@@ -135,8 +140,13 @@ define void @f_with_offset(ptr noalias %b, ptr noalias %c, ptr noalias %d, ptr n
; CHECK-NEXT: br label [[FOR_BODY_LVER_CHECK:%.*]]
; CHECK: for.body.lver.check:
; CHECK-NEXT: [[TMP0:%.*]] = add i64 [[N:%.*]], -1
+; CHECK-NEXT: [[TMP2:%.*]] = trunc i64 [[TMP0]] to i32
+; CHECK-NEXT: [[MUL1:%.*]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 2, i32 [[TMP2]])
+; CHECK-NEXT: [[MUL_RESULT:%.*]] = extractvalue { i32, i1 } [[MUL1]], 0
+; CHECK-NEXT: [[MUL_OVERFLOW:%.*]] = extractvalue { i32, i1 } [[MUL1]], 1
; CHECK-NEXT: [[TMP1:%.*]] = icmp ugt i64 [[TMP0]], 4294967295
-; CHECK-NEXT: br i1 [[TMP1]], label [[FOR_BODY_PH_LVER_ORIG:%.*]], label [[FOR_BODY_PH_LDIST1:%.*]]
+; CHECK-NEXT: [[TMP3:%.*]] = or i1 [[MUL_OVERFLOW]], [[TMP1]]
+; CHECK-NEXT: br i1 [[TMP3]], label [[FOR_BODY_PH_LVER_ORIG:%.*]], label [[FOR_BODY_PH_LDIST1:%.*]]
; CHECK: for.body.ph.lver.orig:
; CHECK-NEXT: br label [[FOR_BODY_LVER_ORIG:%.*]]
; CHECK: for.body.lver.orig:
@@ -200,7 +210,7 @@ define void @f_with_offset(ptr noalias %b, ptr noalias %c, ptr noalias %d, ptr n
; CHECK-NEXT: br i1 [[EXITCOND]], label [[FOR_END_LOOPEXIT2:%.*]], label [[FOR_BODY]]
; CHECK: for.end.loopexit:
; CHECK-NEXT: br label [[FOR_END:%.*]]
-; CHECK: for.end.loopexit1:
+; CHECK: for.end.loopexit2:
; CHECK-NEXT: br label [[FOR_END]]
; CHECK: for.end:
; CHECK-NEXT: ret void
diff --git a/llvm/test/Transforms/LoopVectorize/X86/cost-model.ll b/llvm/test/Transforms/LoopVectorize/X86/cost-model.ll
index 147e949808b54..c1566c4dd32bf 100644
--- a/llvm/test/Transforms/LoopVectorize/X86/cost-model.ll
+++ b/llvm/test/Transforms/LoopVectorize/X86/cost-model.ll
@@ -1045,8 +1045,8 @@ define i64 @live_in_known_1_via_scev() {
; CHECK-NEXT: [[INDEX:%.*]] = phi i32 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
; CHECK-NEXT: [[VEC_PHI:%.*]] = phi <4 x i64> [ <i64 3, i64 1, i64 1, i64 1>, [[VECTOR_PH]] ], [ [[VEC_PHI]], [[VECTOR_BODY]] ]
; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i32 [[INDEX]], 4
-; CHECK-NEXT: [[TMP2:%.*]] = icmp eq i32 [[INDEX_NEXT]], 8
-; CHECK-NEXT: br i1 [[TMP2]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP24:![0-9]+]]
+; CHECK-NEXT: [[TMP0:%.*]] = icmp eq i32 [[INDEX_NEXT]], 8
+; CHECK-NEXT: br i1 [[TMP0]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP24:![0-9]+]]
; CHECK: middle.block:
; CHECK-NEXT: [[TMP3:%.*]] = call i64 @llvm.vector.reduce.mul.v4i64(<4 x i64> [[VEC_PHI]])
; CHECK-NEXT: br label [[EXIT:%.*]]
@@ -1213,6 +1213,7 @@ define i32 @g(i64 %n) {
; CHECK-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i32 [[TMP1]], 4
; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label [[VEC_EPILOG_SCALAR_PH:%.*]], label [[VECTOR_SCEVCHECK:%.*]]
; CHECK: vector.scevcheck:
+; CHECK-NEXT: [[TMP28:%.*]] = trunc i64 [[N]] to i32
; CHECK-NEXT: [[TMP2:%.*]] = icmp ugt i64 [[N]], 4294967295
; CHECK-NEXT: br i1 [[TMP2]], label [[VEC_EPILOG_SCALAR_PH]], label [[VECTOR_MAIN_LOOP_ITER_CHECK:%.*]]
; CHECK: vector.main.loop.iter.check:
diff --git a/llvm/test/Transforms/LoopVectorize/interleaved-accesses-requiring-scev-predicates.ll b/llvm/test/Transforms/LoopVectorize/interleaved-accesses-requiring-scev-predicates.ll
index f0b89d498e45c..38438941eb357 100644
--- a/llvm/test/Transforms/LoopVectorize/interleaved-accesses-requiring-scev-predicates.ll
+++ b/llvm/test/Transforms/LoopVectorize/interleaved-accesses-requiring-scev-predicates.ll
@@ -120,12 +120,16 @@ exit:
; For %gep, we have the following SCEV: ((4 * (zext i4 {0,+,5}<%loop> to i64))<nuw><nsw> + %x).
; Note the i4 bit wide AddRec {0,+,5}. It is known to wrap in the loop with trip count 16.
-; FIXME: Currently we incorrectly assume the widened AddRec does not wrap.
define void @wrap_predicate_for_interleave_group_wraps_for_known_trip_count(ptr noalias %x, ptr noalias %out) {
; CHECK-LABEL: define void @wrap_predicate_for_interleave_group_wraps_for_known_trip_count(
; CHECK-SAME: ptr noalias [[X:%.*]], ptr noalias [[OUT:%.*]]) {
; CHECK-NEXT: [[START:.*]]:
-; CHECK-NEXT: br i1 false, label %[[SCALAR_PH:.*]], label %[[VECTOR_PH:.*]]
+; CHECK-NEXT: br i1 false, label %[[SCALAR_PH:.*]], label %[[VECTOR_SCEVCHECK:.*]]
+; CHECK: [[VECTOR_SCEVCHECK]]:
+; CHECK-NEXT: [[MUL:%.*]] = call { i4, i1 } @llvm.umul.with.overflow.i4(i4 5, i4 -1)
+; CHECK-NEXT: [[MUL_RESULT:%.*]] = extractvalue { i4, i1 } [[MUL]], 0
+; CHECK-NEXT: [[MUL_OVERFLOW:%.*]] = extractvalue { i4, i1 } [[MUL]], 1
+; CHECK-NEXT: br i1 [[MUL_OVERFLOW]], label %[[SCALAR_PH]], label %[[VECTOR_PH:.*]]
; CHECK: [[VECTOR_PH]]:
; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
; CHECK: [[VECTOR_BODY]]:
@@ -144,7 +148,7 @@ define void @wrap_predicate_for_interleave_group_wraps_for_known_trip_count(ptr
; CHECK: [[MIDDLE_BLOCK]]:
; CHECK-NEXT: br label %[[SCALAR_PH]]
; CHECK: [[SCALAR_PH]]:
-; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i64 [ 12, %[[MIDDLE_BLOCK]] ], [ 0, %[[START]] ]
+; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i64 [ 12, %[[MIDDLE_BLOCK]] ], [ 0, %[[START]] ], [ 0, %[[VECTOR_SCEVCHECK]] ]
; CHECK-NEXT: br label %[[LOOP:.*]]
; CHECK: [[LOOP]]:
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[BC_RESUME_VAL]], %[[SCALAR_PH]] ], [ [[IV_NEXT:%.*]], %[[LOOP]] ]
@@ -189,8 +193,13 @@ define void @wrap_predicate_for_interleave_group_unknown_trip_count(ptr noalias
; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label %[[SCALAR_PH:.*]], label %[[VECTOR_SCEVCHECK:.*]]
; CHECK: [[VECTOR_SCEVCHECK]]:
; CHECK-NEXT: [[TMP0:%.*]] = add i64 [[N]], -1
+; CHECK-NEXT: [[TMP9:%.*]] = trunc i64 [[TMP0]] to i4
+; CHECK-NEXT: [[MUL:%.*]] = call { i4, i1 } @llvm.umul.with.overflow.i4(i4 3, i4 [[TMP9]])
+; CHECK-NEXT: [[MUL_RESULT:%.*]] = extractvalue { i4, i1 } [[MUL]], 0
+; CHECK-NEXT: [[MUL_OVERFLOW:%.*]] = extractvalue { i4, i1 } [[MUL]], 1
; CHECK-NEXT: [[TMP1:%.*]] = icmp ugt i64 [[TMP0]], 15
-; CHECK-NEXT: br i1 [[TMP1]], label %[[SCALAR_PH]], label %[[VECTOR_PH:.*]]
+; CHECK-NEXT: [[TMP10:%.*]] = or i1 [[MUL_OVERFLOW]], [[TMP1]]
+; CHECK-NEXT: br i1 [[TMP10]], label %[[SCALAR_PH]], label %[[VECTOR_PH:.*]]
; CHECK: [[VECTOR_PH]]:
; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[N]], 4
; CHECK-NEXT: [[TMP2:%.*]] = icmp eq i64 [[N_MOD_VF]], 0
diff --git a/llvm/test/Transforms/LoopVectorize/runtime-check-small-clamped-bounds.ll b/llvm/test/Transforms/LoopVectorize/runtime-check-small-clamped-bounds.ll
index a47037c46eedc..7a5cf4576ac9e 100644
--- a/llvm/test/Transforms/LoopVectorize/runtime-check-small-clamped-bounds.ll
+++ b/llvm/test/Transforms/LoopVectorize/runtime-check-small-clamped-bounds.ll
@@ -19,6 +19,7 @@ define void @load_clamped_index(ptr %A, ptr %B, i32 %N) {
; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label [[SCALAR_PH:%.*]], label [[VECTOR_SCEVCHECK:%.*]]
; CHECK: vector.scevcheck:
; CHECK-NEXT: [[TMP0:%.*]] = add i32 [[N]], -1
+; CHECK-NEXT: [[TMP3:%.*]] = trunc i32 [[TMP0]] to i2
; CHECK-NEXT: [[TMP1:%.*]] = icmp ugt i32 [[TMP0]], 3
; CHECK-NEXT: br i1 [[TMP1]], label [[SCALAR_PH]], label [[VECTOR_MEMCHECK:%.*]]
; CHECK: vector.memcheck:
@@ -91,6 +92,7 @@ define void @store_clamped_index(ptr %A, ptr %B, i32 %N) {
; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label [[SCALAR_PH:%.*]], label [[VECTOR_SCEVCHECK:%.*]]
; CHECK: vector.scevcheck:
; CHECK-NEXT: [[TMP0:%.*]] = add i32 [[N]], -1
+; CHECK-NEXT: [[TMP3:%.*]] = trunc i32 [[TMP0]] to i2
; CHECK-NEXT: [[TMP1:%.*]] = icmp ugt i32 [[TMP0]], 3
; CHECK-NEXT: br i1 [[TMP1]], label [[SCALAR_PH]], label [[VECTOR_MEMCHECK:%.*]]
; CHECK: vector.memcheck:
@@ -359,6 +361,7 @@ define void @clamped_index_equal_dependence(ptr %A, ptr %B, i32 %N) {
; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label [[SCALAR_PH:%.*]], label [[VECTOR_SCEVCHECK:%.*]]
; CHECK: vector.scevcheck:
; CHECK-NEXT: [[TMP0:%.*]] = add i32 [[N]], -1
+; CHECK-NEXT: [[TMP2:%.*]] = trunc i32 [[TMP0]] to i2
; CHECK-NEXT: [[TMP1:%.*]] = icmp ugt i32 [[TMP0]], 3
; CHECK-NEXT: br i1 [[TMP1]], label [[SCALAR_PH]], label [[VECTOR_PH:%.*]]
; CHECK: vector.ph:
diff --git a/llvm/test/Transforms/LoopVersioning/wrapping-pointer-versioning.ll b/llvm/test/Transforms/LoopVersioning/wrapping-pointer-versioning.ll
index 6e5eeaf9f1218..3e25695304854 100644
--- a/llvm/test/Transforms/LoopVersioning/wrapping-pointer-versioning.ll
+++ b/llvm/test/Transforms/LoopVersioning/wrapping-pointer-versioning.ll
@@ -29,7 +29,12 @@ define void @f1(ptr noalias %a,
; LV-LABEL: @f1(
; LV-NEXT: for.body.lver.check:
; LV-NEXT: [[TMP0:%.*]] = add i64 [[N:%.*]], -1
+; LV-NEXT: [[TMP5:%.*]] = trunc i64 [[TMP0]] to i32
+; LV-NEXT: [[MUL2:%.*]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 2, i32 [[TMP5]])
+; LV-NEXT: [[MUL_RESULT1:%.*]] = extractvalue { i32, i1 } [[MUL2]], 0
+; LV-NEXT: [[MUL_OVERFLOW1:%.*]] = extractvalue { i32, i1 } [[MUL2]], 1
; LV-NEXT: [[TMP1:%.*]] = icmp ugt i64 [[TMP0]], 4294967295
+; LV-NEXT: [[TMP8:%.*]] = or i1 [[MUL_OVERFLOW1]], [[TMP1]]
; LV-NEXT: [[MUL1:%.*]] = call { i64, i1 } @llvm.umul.with.overflow.i64(i64 4, i64 [[TMP0]])
; LV-NEXT: [[MUL_RESULT:%.*]] = extractvalue { i64, i1 } [[MUL1]], 0
; LV-NEXT: [[MUL_OVERFLOW:%.*]] = extractvalue { i64, i1 } [[MUL1]], 1
@@ -37,7 +42,7 @@ define void @f1(ptr noalias %a,
; LV-NEXT: [[TMP3:%.*]] = getelementptr i8, ptr [[A:%.*]], i64 [[MUL_RESULT]]
; LV-NEXT: [[TMP4:%.*]] = icmp ult ptr [[TMP3]], [[A]]
; LV-NEXT: [[TMP6:%.*]] = or i1 [[TMP4]], [[MUL_OVERFLOW]]
-; LV-NEXT: [[TMP7:%.*]] = or i1 [[TMP1]], [[TMP6]]
+; LV-NEXT: [[TMP7:%.*]] = or i1 [[TMP8]], [[TMP6]]
; LV-NEXT: br i1 [[TMP7]], label [[FOR_BODY_PH_LVER_ORIG:%.*]], label [[FOR_BODY_PH:%.*]]
; LV: for.body.ph.lver.orig:
; LV-NEXT: br label [[FOR_BODY_LVER_ORIG:%.*]]
@@ -75,7 +80,7 @@ define void @f1(ptr noalias %a,
; LV-NEXT: br i1 [[EXITCOND]], label [[FOR_END_LOOPEXIT2:%.*]], label [[FOR_BODY]]
; LV: for.end.loopexit:
; LV-NEXT: br label [[FOR_END:%.*]]
-; LV: for.end.loopexit2:
+; LV: for.end.loopexit5:
; LV-NEXT: br label [[FOR_END]]
; LV: for.end:
; LV-NEXT: ret void
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