[llvm] [SCEV] Preserve divisor info when adding guard info for ICMP_NE via Sub. (PR #163250)
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Sun Oct 19 11:24:48 PDT 2025
https://github.com/fhahn updated https://github.com/llvm/llvm-project/pull/163250
>From 3e424b4f584b0d9511c5f5c124ff0c7fb28a4002 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Mon, 13 Oct 2025 19:58:27 +0100
Subject: [PATCH 1/3] [SCEV] Preserve divisor info when adding guard info for
ICMP_NE via Sub.
Follow-up to https://github.com/llvm/llvm-project/pull/160500 to
preserve divisibiltiy info when creating the UMax.
---
llvm/lib/Analysis/ScalarEvolution.cpp | 47 +++++-----
.../max-backedge-taken-count-guard-info.ll | 8 +-
.../single-early-exit-deref-assumptions.ll | 92 +++++++++++++++++--
3 files changed, 112 insertions(+), 35 deletions(-)
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 425420fd698ef..af413ecbf49bf 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -15473,6 +15473,22 @@ void ScalarEvolution::LoopGuards::collectFromPHI(
}
}
+ // Return a new SCEV that modifies \p Expr to the closest number divides by
+ // \p Divisor and greater or equal than Expr. For now, only handle constant
+ // Expr.
+static const SCEV *getNextSCEVDividesByDivisor(const SCEV *Expr,
+ const APInt &DivisorVal, ScalarEvolution &SE) {
+ const APInt *ExprVal;
+ if (!match(Expr, m_scev_APInt(ExprVal)) || ExprVal->isNegative() ||
+ DivisorVal.isNonPositive())
+ return Expr;
+ APInt Rem = ExprVal->urem(DivisorVal);
+ if (Rem.isZero())
+ return Expr;
+ // return the SCEV: Expr + Divisor - Expr % Divisor
+ return SE.getConstant(*ExprVal + DivisorVal - Rem);
+ }
+
void ScalarEvolution::LoopGuards::collectFromBlock(
ScalarEvolution &SE, ScalarEvolution::LoopGuards &Guards,
const BasicBlock *Block, const BasicBlock *Pred,
@@ -15540,22 +15556,6 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
match(LHS, m_scev_APInt(C)) && C->isNonNegative();
};
- // Return a new SCEV that modifies \p Expr to the closest number divides by
- // \p Divisor and greater or equal than Expr. For now, only handle constant
- // Expr.
- auto GetNextSCEVDividesByDivisor = [&](const SCEV *Expr,
- const APInt &DivisorVal) {
- const APInt *ExprVal;
- if (!match(Expr, m_scev_APInt(ExprVal)) || ExprVal->isNegative() ||
- DivisorVal.isNonPositive())
- return Expr;
- APInt Rem = ExprVal->urem(DivisorVal);
- if (Rem.isZero())
- return Expr;
- // return the SCEV: Expr + Divisor - Expr % Divisor
- return SE.getConstant(*ExprVal + DivisorVal - Rem);
- };
-
// Return a new SCEV that modifies \p Expr to the closest number divides by
// \p Divisor and less or equal than Expr. For now, only handle constant
// Expr.
@@ -15592,7 +15592,7 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
"Expected non-negative operand!");
auto *DivisibleExpr =
IsMin ? GetPreviousSCEVDividesByDivisor(MinMaxLHS, DivisorVal)
- : GetNextSCEVDividesByDivisor(MinMaxLHS, DivisorVal);
+ : getNextSCEVDividesByDivisor(MinMaxLHS, DivisorVal, SE);
SmallVector<const SCEV *> Ops = {
ApplyDivisibiltyOnMinMaxExpr(MinMaxRHS, Divisor), DivisibleExpr};
return SE.getMinMaxExpr(SCTy, Ops);
@@ -15675,7 +15675,7 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
case CmpInst::ICMP_UGT:
case CmpInst::ICMP_SGT:
RHS = SE.getAddExpr(RHS, One);
- RHS = GetNextSCEVDividesByDivisor(RHS, DividesBy);
+ RHS = getNextSCEVDividesByDivisor(RHS, DividesBy, SE);
break;
case CmpInst::ICMP_ULE:
case CmpInst::ICMP_SLE:
@@ -15683,7 +15683,7 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
break;
case CmpInst::ICMP_UGE:
case CmpInst::ICMP_SGE:
- RHS = GetNextSCEVDividesByDivisor(RHS, DividesBy);
+ RHS = getNextSCEVDividesByDivisor(RHS, DividesBy, SE);
break;
default:
break;
@@ -15737,7 +15737,7 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
case CmpInst::ICMP_NE:
if (match(RHS, m_scev_Zero())) {
const SCEV *OneAlignedUp =
- GetNextSCEVDividesByDivisor(One, DividesBy);
+ getNextSCEVDividesByDivisor(One, DividesBy, SE);
To = SE.getUMaxExpr(FromRewritten, OneAlignedUp);
} else {
// LHS != RHS can be rewritten as (LHS - RHS) = UMax(1, LHS - RHS),
@@ -15963,8 +15963,11 @@ const SCEV *ScalarEvolution::LoopGuards::rewrite(const SCEV *Expr) const {
if (MatchBinarySub(S, LHS, RHS)) {
if (LHS > RHS)
std::swap(LHS, RHS);
- if (NotEqual.contains({LHS, RHS}))
- return SE.getUMaxExpr(S, SE.getOne(S->getType()));
+ if (NotEqual.contains({LHS, RHS})){
+ const SCEV *OneAlignedUp = getNextSCEVDividesByDivisor(
+ SE.getOne(S->getType()), SE.getConstantMultiple(S), SE);
+ return SE.getUMaxExpr(OneAlignedUp , S);
+ }
}
return nullptr;
};
diff --git a/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll b/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
index 4024c986dd11d..d5a2181e9bc5e 100644
--- a/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
+++ b/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
@@ -1431,7 +1431,7 @@ define void @ptr_induction_early_exit_eq_1_with_align_on_load(ptr %a, ptr %b, pt
; CHECK-NEXT: Loop %loop: <multiple exits> Unpredictable backedge-taken count.
; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
-; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693951
+; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693950
; CHECK-NEXT: Loop %loop: symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
@@ -1470,7 +1470,7 @@ define void @ptr_induction_early_exit_eq_1_with_align_on_arguments(ptr align 8 %
; CHECK-NEXT: Loop %loop: <multiple exits> Unpredictable backedge-taken count.
; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a to i64)) + (ptrtoint ptr %b to i64)) /u 8)
-; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693951
+; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693950
; CHECK-NEXT: Loop %loop: symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a to i64)) + (ptrtoint ptr %b to i64)) /u 8)
; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a to i64)) + (ptrtoint ptr %b to i64)) /u 8)
@@ -1511,7 +1511,7 @@ define void @ptr_induction_early_exit_eq_1_align_assumption_1(ptr %a, ptr %b, pt
; CHECK-NEXT: Loop %loop: <multiple exits> Unpredictable backedge-taken count.
; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
-; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693951
+; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693950
; CHECK-NEXT: Loop %loop: symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
@@ -1556,7 +1556,7 @@ define void @ptr_induction_early_exit_eq_1_align_assumption_2(ptr %a, ptr %b, pt
; CHECK-NEXT: Loop %loop: <multiple exits> Unpredictable backedge-taken count.
; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
-; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693951
+; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693950
; CHECK-NEXT: Loop %loop: symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
diff --git a/llvm/test/Transforms/LoopVectorize/single-early-exit-deref-assumptions.ll b/llvm/test/Transforms/LoopVectorize/single-early-exit-deref-assumptions.ll
index cc3bda4a7f43b..dfe3f5dc03dc5 100644
--- a/llvm/test/Transforms/LoopVectorize/single-early-exit-deref-assumptions.ll
+++ b/llvm/test/Transforms/LoopVectorize/single-early-exit-deref-assumptions.ll
@@ -401,18 +401,55 @@ define ptr @find_deref_pointer_distance_align_attribute_argument(ptr align 2 %fi
; CHECK-NEXT: [[C_0:%.*]] = icmp eq ptr [[FIRST]], [[LAST]]
; CHECK-NEXT: br i1 [[C_0]], label %[[EXIT:.*]], label %[[LOOP_HEADER_PREHEADER:.*]]
; CHECK: [[LOOP_HEADER_PREHEADER]]:
+; CHECK-NEXT: [[TMP0:%.*]] = add i64 [[LAST_I64]], -2
+; CHECK-NEXT: [[TMP1:%.*]] = sub i64 [[TMP0]], [[FIRST_I64]]
+; CHECK-NEXT: [[TMP2:%.*]] = lshr i64 [[TMP1]], 1
+; CHECK-NEXT: [[TMP3:%.*]] = add nuw i64 [[TMP2]], 1
+; CHECK-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[TMP3]], 4
+; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label %[[SCALAR_PH:.*]], label %[[VECTOR_PH:.*]]
+; CHECK: [[VECTOR_PH]]:
+; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[TMP3]], 4
+; CHECK-NEXT: [[N_VEC:%.*]] = sub i64 [[TMP3]], [[N_MOD_VF]]
+; CHECK-NEXT: [[TMP4:%.*]] = mul i64 [[N_VEC]], 2
+; CHECK-NEXT: [[TMP5:%.*]] = getelementptr i8, ptr [[FIRST]], i64 [[TMP4]]
+; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
+; CHECK: [[VECTOR_BODY]]:
+; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT: [[OFFSET_IDX:%.*]] = mul i64 [[INDEX]], 2
+; CHECK-NEXT: [[NEXT_GEP:%.*]] = getelementptr i8, ptr [[FIRST]], i64 [[OFFSET_IDX]]
+; CHECK-NEXT: [[WIDE_LOAD:%.*]] = load <4 x i16>, ptr [[NEXT_GEP]], align 2
+; CHECK-NEXT: [[TMP6:%.*]] = icmp eq <4 x i16> [[WIDE_LOAD]], splat (i16 1)
+; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
+; CHECK-NEXT: [[TMP7:%.*]] = freeze <4 x i1> [[TMP6]]
+; CHECK-NEXT: [[TMP8:%.*]] = call i1 @llvm.vector.reduce.or.v4i1(<4 x i1> [[TMP7]])
+; CHECK-NEXT: [[TMP9:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
+; CHECK-NEXT: [[TMP10:%.*]] = or i1 [[TMP8]], [[TMP9]]
+; CHECK-NEXT: br i1 [[TMP10]], label %[[MIDDLE_SPLIT:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP7:![0-9]+]]
+; CHECK: [[MIDDLE_SPLIT]]:
+; CHECK-NEXT: br i1 [[TMP8]], label %[[VECTOR_EARLY_EXIT:.*]], label %[[MIDDLE_BLOCK:.*]]
+; CHECK: [[MIDDLE_BLOCK]]:
+; CHECK-NEXT: [[CMP_N:%.*]] = icmp eq i64 [[TMP3]], [[N_VEC]]
+; CHECK-NEXT: br i1 [[CMP_N]], label %[[EXIT_LOOPEXIT:.*]], label %[[SCALAR_PH]]
+; CHECK: [[VECTOR_EARLY_EXIT]]:
+; CHECK-NEXT: [[TMP11:%.*]] = call i64 @llvm.experimental.cttz.elts.i64.v4i1(<4 x i1> [[TMP6]], i1 true)
+; CHECK-NEXT: [[TMP12:%.*]] = add i64 [[INDEX]], [[TMP11]]
+; CHECK-NEXT: [[TMP13:%.*]] = mul i64 [[TMP12]], 2
+; CHECK-NEXT: [[TMP14:%.*]] = getelementptr i8, ptr [[FIRST]], i64 [[TMP13]]
+; CHECK-NEXT: br label %[[EXIT_LOOPEXIT]]
+; CHECK: [[SCALAR_PH]]:
+; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi ptr [ [[TMP5]], %[[MIDDLE_BLOCK]] ], [ [[FIRST]], %[[LOOP_HEADER_PREHEADER]] ]
; CHECK-NEXT: br label %[[LOOP_HEADER:.*]]
; CHECK: [[LOOP_HEADER]]:
-; CHECK-NEXT: [[IV:%.*]] = phi ptr [ [[IV_NEXT:%.*]], %[[LOOP_LATCH:.*]] ], [ [[FIRST]], %[[LOOP_HEADER_PREHEADER]] ]
+; CHECK-NEXT: [[IV:%.*]] = phi ptr [ [[IV_NEXT:%.*]], %[[LOOP_LATCH:.*]] ], [ [[BC_RESUME_VAL]], %[[SCALAR_PH]] ]
; CHECK-NEXT: [[L:%.*]] = load i16, ptr [[IV]], align 2
; CHECK-NEXT: [[C_1:%.*]] = icmp eq i16 [[L]], 1
-; CHECK-NEXT: br i1 [[C_1]], label %[[EXIT_LOOPEXIT:.*]], label %[[LOOP_LATCH]]
+; CHECK-NEXT: br i1 [[C_1]], label %[[EXIT_LOOPEXIT]], label %[[LOOP_LATCH]]
; CHECK: [[LOOP_LATCH]]:
; CHECK-NEXT: [[IV_NEXT]] = getelementptr inbounds nuw i8, ptr [[IV]], i64 2
; CHECK-NEXT: [[C_2:%.*]] = icmp eq ptr [[IV_NEXT]], [[LAST]]
-; CHECK-NEXT: br i1 [[C_2]], label %[[EXIT_LOOPEXIT]], label %[[LOOP_HEADER]]
+; CHECK-NEXT: br i1 [[C_2]], label %[[EXIT_LOOPEXIT]], label %[[LOOP_HEADER]], !llvm.loop [[LOOP8:![0-9]+]]
; CHECK: [[EXIT_LOOPEXIT]]:
-; CHECK-NEXT: [[FIRST_ADDR_0_LCSSA_I_PH:%.*]] = phi ptr [ [[IV_NEXT]], %[[LOOP_LATCH]] ], [ [[IV]], %[[LOOP_HEADER]] ]
+; CHECK-NEXT: [[FIRST_ADDR_0_LCSSA_I_PH:%.*]] = phi ptr [ [[IV_NEXT]], %[[LOOP_LATCH]] ], [ [[IV]], %[[LOOP_HEADER]] ], [ [[TMP5]], %[[MIDDLE_BLOCK]] ], [ [[TMP14]], %[[VECTOR_EARLY_EXIT]] ]
; CHECK-NEXT: br label %[[EXIT]]
; CHECK: [[EXIT]]:
; CHECK-NEXT: [[FIRST_ADDR_0_LCSSA_I:%.*]] = phi ptr [ [[FIRST]], %[[ENTRY]] ], [ [[FIRST_ADDR_0_LCSSA_I_PH]], %[[EXIT_LOOPEXIT]] ]
@@ -458,18 +495,55 @@ define ptr @find_deref_pointer_distance_align_assumption(ptr %first, ptr %last)
; CHECK-NEXT: [[C_0:%.*]] = icmp eq ptr [[FIRST]], [[LAST]]
; CHECK-NEXT: br i1 [[C_0]], label %[[EXIT:.*]], label %[[LOOP_HEADER_PREHEADER:.*]]
; CHECK: [[LOOP_HEADER_PREHEADER]]:
+; CHECK-NEXT: [[TMP0:%.*]] = add i64 [[LAST_I64]], -2
+; CHECK-NEXT: [[TMP1:%.*]] = sub i64 [[TMP0]], [[FIRST_I64]]
+; CHECK-NEXT: [[TMP2:%.*]] = lshr i64 [[TMP1]], 1
+; CHECK-NEXT: [[TMP3:%.*]] = add nuw i64 [[TMP2]], 1
+; CHECK-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[TMP3]], 4
+; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label %[[SCALAR_PH:.*]], label %[[VECTOR_PH:.*]]
+; CHECK: [[VECTOR_PH]]:
+; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[TMP3]], 4
+; CHECK-NEXT: [[N_VEC:%.*]] = sub i64 [[TMP3]], [[N_MOD_VF]]
+; CHECK-NEXT: [[TMP4:%.*]] = mul i64 [[N_VEC]], 2
+; CHECK-NEXT: [[TMP5:%.*]] = getelementptr i8, ptr [[FIRST]], i64 [[TMP4]]
+; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
+; CHECK: [[VECTOR_BODY]]:
+; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT: [[OFFSET_IDX:%.*]] = mul i64 [[INDEX]], 2
+; CHECK-NEXT: [[NEXT_GEP:%.*]] = getelementptr i8, ptr [[FIRST]], i64 [[OFFSET_IDX]]
+; CHECK-NEXT: [[WIDE_LOAD:%.*]] = load <4 x i16>, ptr [[NEXT_GEP]], align 2
+; CHECK-NEXT: [[TMP6:%.*]] = icmp eq <4 x i16> [[WIDE_LOAD]], splat (i16 1)
+; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
+; CHECK-NEXT: [[TMP7:%.*]] = freeze <4 x i1> [[TMP6]]
+; CHECK-NEXT: [[TMP8:%.*]] = call i1 @llvm.vector.reduce.or.v4i1(<4 x i1> [[TMP7]])
+; CHECK-NEXT: [[TMP9:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
+; CHECK-NEXT: [[TMP10:%.*]] = or i1 [[TMP8]], [[TMP9]]
+; CHECK-NEXT: br i1 [[TMP10]], label %[[MIDDLE_SPLIT:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP9:![0-9]+]]
+; CHECK: [[MIDDLE_SPLIT]]:
+; CHECK-NEXT: br i1 [[TMP8]], label %[[VECTOR_EARLY_EXIT:.*]], label %[[MIDDLE_BLOCK:.*]]
+; CHECK: [[MIDDLE_BLOCK]]:
+; CHECK-NEXT: [[CMP_N:%.*]] = icmp eq i64 [[TMP3]], [[N_VEC]]
+; CHECK-NEXT: br i1 [[CMP_N]], label %[[EXIT_LOOPEXIT:.*]], label %[[SCALAR_PH]]
+; CHECK: [[VECTOR_EARLY_EXIT]]:
+; CHECK-NEXT: [[TMP11:%.*]] = call i64 @llvm.experimental.cttz.elts.i64.v4i1(<4 x i1> [[TMP6]], i1 true)
+; CHECK-NEXT: [[TMP12:%.*]] = add i64 [[INDEX]], [[TMP11]]
+; CHECK-NEXT: [[TMP13:%.*]] = mul i64 [[TMP12]], 2
+; CHECK-NEXT: [[TMP14:%.*]] = getelementptr i8, ptr [[FIRST]], i64 [[TMP13]]
+; CHECK-NEXT: br label %[[EXIT_LOOPEXIT]]
+; CHECK: [[SCALAR_PH]]:
+; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi ptr [ [[TMP5]], %[[MIDDLE_BLOCK]] ], [ [[FIRST]], %[[LOOP_HEADER_PREHEADER]] ]
; CHECK-NEXT: br label %[[LOOP_HEADER:.*]]
; CHECK: [[LOOP_HEADER]]:
-; CHECK-NEXT: [[IV:%.*]] = phi ptr [ [[IV_NEXT:%.*]], %[[LOOP_LATCH:.*]] ], [ [[FIRST]], %[[LOOP_HEADER_PREHEADER]] ]
+; CHECK-NEXT: [[IV:%.*]] = phi ptr [ [[IV_NEXT:%.*]], %[[LOOP_LATCH:.*]] ], [ [[BC_RESUME_VAL]], %[[SCALAR_PH]] ]
; CHECK-NEXT: [[L:%.*]] = load i16, ptr [[IV]], align 2
; CHECK-NEXT: [[C_1:%.*]] = icmp eq i16 [[L]], 1
-; CHECK-NEXT: br i1 [[C_1]], label %[[EXIT_LOOPEXIT:.*]], label %[[LOOP_LATCH]]
+; CHECK-NEXT: br i1 [[C_1]], label %[[EXIT_LOOPEXIT]], label %[[LOOP_LATCH]]
; CHECK: [[LOOP_LATCH]]:
; CHECK-NEXT: [[IV_NEXT]] = getelementptr inbounds nuw i8, ptr [[IV]], i64 2
; CHECK-NEXT: [[C_2:%.*]] = icmp eq ptr [[IV_NEXT]], [[LAST]]
-; CHECK-NEXT: br i1 [[C_2]], label %[[EXIT_LOOPEXIT]], label %[[LOOP_HEADER]]
+; CHECK-NEXT: br i1 [[C_2]], label %[[EXIT_LOOPEXIT]], label %[[LOOP_HEADER]], !llvm.loop [[LOOP10:![0-9]+]]
; CHECK: [[EXIT_LOOPEXIT]]:
-; CHECK-NEXT: [[FIRST_ADDR_0_LCSSA_I_PH:%.*]] = phi ptr [ [[IV_NEXT]], %[[LOOP_LATCH]] ], [ [[IV]], %[[LOOP_HEADER]] ]
+; CHECK-NEXT: [[FIRST_ADDR_0_LCSSA_I_PH:%.*]] = phi ptr [ [[IV_NEXT]], %[[LOOP_LATCH]] ], [ [[IV]], %[[LOOP_HEADER]] ], [ [[TMP5]], %[[MIDDLE_BLOCK]] ], [ [[TMP14]], %[[VECTOR_EARLY_EXIT]] ]
; CHECK-NEXT: br label %[[EXIT]]
; CHECK: [[EXIT]]:
; CHECK-NEXT: [[FIRST_ADDR_0_LCSSA_I:%.*]] = phi ptr [ [[FIRST]], %[[ENTRY]] ], [ [[FIRST_ADDR_0_LCSSA_I_PH]], %[[EXIT_LOOPEXIT]] ]
@@ -522,7 +596,7 @@ define i64 @early_exit_alignment_and_deref_known_via_assumption_with_constant_si
; CHECK-NEXT: [[TMP4:%.*]] = call i1 @llvm.vector.reduce.or.v4i1(<4 x i1> [[TMP3]])
; CHECK-NEXT: [[TMP5:%.*]] = icmp eq i64 [[INDEX_NEXT3]], 1024
; CHECK-NEXT: [[TMP6:%.*]] = or i1 [[TMP4]], [[TMP5]]
-; CHECK-NEXT: br i1 [[TMP6]], label %[[MIDDLE_SPLIT:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP7:![0-9]+]]
+; CHECK-NEXT: br i1 [[TMP6]], label %[[MIDDLE_SPLIT:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP11:![0-9]+]]
; CHECK: [[MIDDLE_SPLIT]]:
; CHECK-NEXT: br i1 [[TMP4]], label %[[VECTOR_EARLY_EXIT:.*]], label %[[MIDDLE_BLOCK:.*]]
; CHECK: [[MIDDLE_BLOCK]]:
>From 7af447d04f0eb10713f9b377f592979cdfc850b8 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Sun, 19 Oct 2025 19:22:37 +0100
Subject: [PATCH 2/3] !fixup fix formatting
---
llvm/lib/Analysis/ScalarEvolution.cpp | 35 ++++++++++++++-------------
1 file changed, 18 insertions(+), 17 deletions(-)
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index af413ecbf49bf..c4eb83868582c 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -15473,21 +15473,22 @@ void ScalarEvolution::LoopGuards::collectFromPHI(
}
}
- // Return a new SCEV that modifies \p Expr to the closest number divides by
- // \p Divisor and greater or equal than Expr. For now, only handle constant
- // Expr.
+// Return a new SCEV that modifies \p Expr to the closest number divides by
+// \p Divisor and greater or equal than Expr. For now, only handle constant
+// Expr.
static const SCEV *getNextSCEVDividesByDivisor(const SCEV *Expr,
- const APInt &DivisorVal, ScalarEvolution &SE) {
- const APInt *ExprVal;
- if (!match(Expr, m_scev_APInt(ExprVal)) || ExprVal->isNegative() ||
- DivisorVal.isNonPositive())
- return Expr;
- APInt Rem = ExprVal->urem(DivisorVal);
- if (Rem.isZero())
- return Expr;
- // return the SCEV: Expr + Divisor - Expr % Divisor
- return SE.getConstant(*ExprVal + DivisorVal - Rem);
- }
+ const APInt &DivisorVal,
+ ScalarEvolution &SE) {
+ const APInt *ExprVal;
+ if (!match(Expr, m_scev_APInt(ExprVal)) || ExprVal->isNegative() ||
+ DivisorVal.isNonPositive())
+ return Expr;
+ APInt Rem = ExprVal->urem(DivisorVal);
+ if (Rem.isZero())
+ return Expr;
+ // return the SCEV: Expr + Divisor - Expr % Divisor
+ return SE.getConstant(*ExprVal + DivisorVal - Rem);
+}
void ScalarEvolution::LoopGuards::collectFromBlock(
ScalarEvolution &SE, ScalarEvolution::LoopGuards &Guards,
@@ -15963,11 +15964,11 @@ const SCEV *ScalarEvolution::LoopGuards::rewrite(const SCEV *Expr) const {
if (MatchBinarySub(S, LHS, RHS)) {
if (LHS > RHS)
std::swap(LHS, RHS);
- if (NotEqual.contains({LHS, RHS})){
+ if (NotEqual.contains({LHS, RHS})) {
const SCEV *OneAlignedUp = getNextSCEVDividesByDivisor(
SE.getOne(S->getType()), SE.getConstantMultiple(S), SE);
- return SE.getUMaxExpr(OneAlignedUp , S);
- }
+ return SE.getUMaxExpr(OneAlignedUp, S);
+ }
}
return nullptr;
};
>From 015e2f890a1dbb2eb8ca738c8a0ce26c57efca67 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Sun, 19 Oct 2025 19:24:24 +0100
Subject: [PATCH 3/3] !fixup drop TODOs from tests.
---
.../LoopVectorize/single-early-exit-deref-assumptions.ll | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/llvm/test/Transforms/LoopVectorize/single-early-exit-deref-assumptions.ll b/llvm/test/Transforms/LoopVectorize/single-early-exit-deref-assumptions.ll
index dfe3f5dc03dc5..5cdde057da1ad 100644
--- a/llvm/test/Transforms/LoopVectorize/single-early-exit-deref-assumptions.ll
+++ b/llvm/test/Transforms/LoopVectorize/single-early-exit-deref-assumptions.ll
@@ -387,7 +387,7 @@ exit:
ret i64 %res
}
-; TODO: The existing assumptions should be strong enough to vectorize this.
+; The existing assumptions is strong enough to vectorize this.
define ptr @find_deref_pointer_distance_align_attribute_argument(ptr align 2 %first, ptr align 2 %last) nofree nosync {
; CHECK-LABEL: define ptr @find_deref_pointer_distance_align_attribute_argument(
; CHECK-SAME: ptr align 2 [[FIRST:%.*]], ptr align 2 [[LAST:%.*]]) #[[ATTR0]] {
@@ -481,7 +481,7 @@ exit:
ret ptr %first.addr.0.lcssa.i
}
-; TODO: The existing assumptions should be strong enough to vectorize this.
+; The existing assumptions is strong enough to vectorize this.
define ptr @find_deref_pointer_distance_align_assumption(ptr %first, ptr %last) nofree nosync {
; CHECK-LABEL: define ptr @find_deref_pointer_distance_align_assumption(
; CHECK-SAME: ptr [[FIRST:%.*]], ptr [[LAST:%.*]]) #[[ATTR0]] {
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