[llvm] [SCEV] Fix non-NFC parts of getOrCreateUDiv patch (PR #217428)
Ramkumar Ramachandra via llvm-commits
llvm-commits at lists.llvm.org
Wed Aug 19 11:38:31 PDT 2026
https://github.com/artagnon created https://github.com/llvm/llvm-project/pull/217428
Follow up on db04516 ([SCEV] Introduce getOrCreateUDivExpr, #216832) to fix its non-NFC parts.
>From afa315504f9d4ffa2dc7246bb7ffcbff3e7a136e Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <artagnon at tenstorrent.com>
Date: Wed, 19 Aug 2026 19:34:23 +0100
Subject: [PATCH 1/2] [SCEV] Pre-commit test
---
llvm/test/Analysis/ScalarEvolution/udiv.ll | 64 ++++++++++++++++++++++
1 file changed, 64 insertions(+)
diff --git a/llvm/test/Analysis/ScalarEvolution/udiv.ll b/llvm/test/Analysis/ScalarEvolution/udiv.ll
index 7defe258b29de..6a5dff3f99e33 100644
--- a/llvm/test/Analysis/ScalarEvolution/udiv.ll
+++ b/llvm/test/Analysis/ScalarEvolution/udiv.ll
@@ -123,3 +123,67 @@ define i8 @udiv_mul_by_factor_not_nuw(i8 %x, i8 %y) {
%div = udiv i8 %mul, %y
ret i8 %div
}
+
+declare i1 @cond()
+
+define void @get_or_create(i64 %n, ptr %p, ptr noalias %q) {
+; CHECK-LABEL: 'get_or_create'
+; CHECK-NEXT: Classifying expressions for: @get_or_create
+; CHECK-NEXT: %k = phi i64 [ 0, %entry ], [ %k.next, %outer.latch ]
+; CHECK-NEXT: --> {0,+,1}<%outer.header> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %outer.header: Computable, %loop: Invariant }
+; CHECK-NEXT: %aligned = shl i64 %k, 4
+; CHECK-NEXT: --> {0,+,16}<%outer.header> U: [0,-15) S: [-9223372036854775808,9223372036854775793) Exits: <<Unknown>> LoopDispositions: { %outer.header: Computable, %loop: Invariant }
+; CHECK-NEXT: %start = add i64 %aligned, 1
+; CHECK-NEXT: --> {1,+,16}<%outer.header> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %outer.header: Computable, %loop: Invariant }
+; CHECK-NEXT: %iv = phi i64 [ %start, %outer.header ], [ %iv.next, %loop ]
+; CHECK-NEXT: --> {{\{\{}}1,+,16}<%outer.header>,+,4}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable, %outer.header: Variant }
+; CHECK-NEXT: %j = phi i64 [ %aligned, %outer.header ], [ %j.next, %loop ]
+; CHECK-NEXT: --> {{\{\{}}0,+,16}<%outer.header>,+,4}<nuw><%loop> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: <<Unknown>> LoopDispositions: { %loop: Computable, %outer.header: Variant }
+; CHECK-NEXT: %div = udiv i64 %iv, 4
+; CHECK-NEXT: --> {({0,+,16}<%outer.header> /u 4),+,1}<nw><%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable, %outer.header: Variant }
+; CHECK-NEXT: %iv.next = add i64 %iv, 4
+; CHECK-NEXT: --> {{\{\{}}5,+,16}<%outer.header>,+,4}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable, %outer.header: Variant }
+; CHECK-NEXT: %j.next = add nuw i64 %j, 4
+; CHECK-NEXT: --> {{\{\{}}4,+,16}<%outer.header>,+,4}<nw><%loop> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: <<Unknown>> LoopDispositions: { %loop: Computable, %outer.header: Variant }
+; CHECK-NEXT: %c = call i1 @cond()
+; CHECK-NEXT: --> %c U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant, %outer.header: Variant }
+; CHECK-NEXT: %k.next = add i64 %k, 1
+; CHECK-NEXT: --> {1,+,1}<%outer.header> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %outer.header: Computable, %loop: Invariant }
+; CHECK-NEXT: %ec = call i1 @cond()
+; CHECK-NEXT: --> %ec U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %outer.header: Variant, %loop: Invariant }
+; CHECK-NEXT: Determining loop execution counts for: @get_or_create
+; CHECK-NEXT: Loop %loop: Unpredictable backedge-taken count.
+; CHECK-NEXT: Loop %loop: Unpredictable constant max backedge-taken count.
+; CHECK-NEXT: Loop %loop: Unpredictable symbolic max backedge-taken count.
+; CHECK-NEXT: Loop %outer.header: Unpredictable backedge-taken count.
+; CHECK-NEXT: Loop %outer.header: Unpredictable constant max backedge-taken count.
+; CHECK-NEXT: Loop %outer.header: Unpredictable symbolic max backedge-taken count.
+;
+entry:
+ br label %outer.header
+
+outer.header:
+ %k = phi i64 [ 0, %entry ], [ %k.next, %outer.latch ]
+ %aligned = shl i64 %k, 4
+ %start = add i64 %aligned, 1
+ br label %loop
+
+loop:
+ %iv = phi i64 [ %start, %outer.header ], [ %iv.next, %loop ]
+ %j = phi i64 [ %aligned, %outer.header ], [ %j.next, %loop ]
+ %div = udiv i64 %iv, 4
+ store volatile i64 %div, ptr %p
+ store volatile i64 %j, ptr %q
+ %iv.next = add i64 %iv, 4
+ %j.next = add nuw i64 %j, 4
+ %c = call i1 @cond()
+ br i1 %c, label %loop, label %outer.latch
+
+outer.latch:
+ %k.next = add i64 %k, 1
+ %ec = call i1 @cond()
+ br i1 %ec, label %outer.header, label %exit
+
+exit:
+ ret void
+}
>From a06d954a00dadeebdc92c29069867de0c9dc0db4 Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <artagnon at tenstorrent.com>
Date: Wed, 19 Aug 2026 19:35:22 +0100
Subject: [PATCH 2/2] [SCEV] Fix non-NFC parts of getOrCreateUDiv patch
Follow up on db04516 ([SCEV] Introduce getOrCreateUDivExpr, #216832) to
fix its non-NFC parts.
---
llvm/lib/Analysis/ScalarEvolution.cpp | 4 +++-
llvm/test/Analysis/ScalarEvolution/udiv.ll | 2 +-
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 52a03d2cad62d..cef4f6cadeb61 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -3573,7 +3573,9 @@ const SCEV *ScalarEvolution::getUDivExpr(SCEVUse LHS, SCEVUse RHS) {
getAddRecExpr(NewStart, Step, AR->getLoop(),
NoWrap ? SCEV::FlagNW : SCEV::FlagAnyWrap);
if (LHS != NewLHS)
- return getUDivExpr(NewLHS, RHS);
+ if (auto *S = findExistingSCEVInCache(
+ scUDivExpr, ArrayRef<SCEVUse>{NewLHS, RHS}))
+ return S;
}
}
}
diff --git a/llvm/test/Analysis/ScalarEvolution/udiv.ll b/llvm/test/Analysis/ScalarEvolution/udiv.ll
index 6a5dff3f99e33..200ff52aada0a 100644
--- a/llvm/test/Analysis/ScalarEvolution/udiv.ll
+++ b/llvm/test/Analysis/ScalarEvolution/udiv.ll
@@ -140,7 +140,7 @@ define void @get_or_create(i64 %n, ptr %p, ptr noalias %q) {
; CHECK-NEXT: %j = phi i64 [ %aligned, %outer.header ], [ %j.next, %loop ]
; CHECK-NEXT: --> {{\{\{}}0,+,16}<%outer.header>,+,4}<nuw><%loop> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: <<Unknown>> LoopDispositions: { %loop: Computable, %outer.header: Variant }
; CHECK-NEXT: %div = udiv i64 %iv, 4
-; CHECK-NEXT: --> {({0,+,16}<%outer.header> /u 4),+,1}<nw><%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable, %outer.header: Variant }
+; CHECK-NEXT: --> ({{\{\{}}1,+,16}<%outer.header>,+,4}<%loop> /u 4) U: [0,4611686018427387904) S: [0,4611686018427387904) Exits: <<Unknown>> LoopDispositions: { %loop: Computable, %outer.header: Variant }
; CHECK-NEXT: %iv.next = add i64 %iv, 4
; CHECK-NEXT: --> {{\{\{}}5,+,16}<%outer.header>,+,4}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable, %outer.header: Variant }
; CHECK-NEXT: %j.next = add nuw i64 %j, 4
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