Skip to content

[SCEV] Use context instruction for SCEVUnknowns in getConstantMultiple. #163260

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Oct 14, 2025
+25 −15
Merged

[SCEV] Use context instruction for SCEVUnknowns in getConstantMultiple. #163260

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
0e94868
[SCEV] Use context instruction for SCEVUnknowns in getConstantMultiple.
fhahn Oct 8, 2025
d3f1bc2
Merge branch 'main' into scev-more-ctx-for-scevunknown
fhahn Oct 14, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
12 changes: 11 additions & 1 deletion llvm/lib/Analysis/ScalarEvolution.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6417,8 +6417,18 @@ APInt ScalarEvolution::getConstantMultipleImpl(const SCEV *S,
case scSequentialUMinExpr:
return GetGCDMultiple(cast<SCEVNAryExpr>(S));
case scUnknown: {
// ask ValueTracking for known bits
// Ask ValueTracking for known bits. SCEVUnknown only become available at
// the point their underlying IR instruction has been defined. If CtxI was
// not provided, use:
// * the first instruction in the entry block if it is an argument
// * the instruction itself otherwise.
const SCEVUnknown *U = cast<SCEVUnknown>(S);
if (!CtxI) {
if (isa<Argument>(U->getValue()))
CtxI = &*F.getEntryBlock().begin();
else if (auto *I = dyn_cast<Instruction>(U->getValue()))
CtxI = I;
}
unsigned Known =
computeKnownBits(U->getValue(), getDataLayout(), &AC, CtxI, &DT)
.countMinTrailingZeros();
Expand Down
28 changes: 14 additions & 14 deletions llvm/test/Analysis/ScalarEvolution/trip-multiple-guard-info.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -578,22 +578,22 @@ define void @test_ptr_aligned_by_2_and_4_via_assumption(ptr %start, ptr %end) {
; CHECK-LABEL: 'test_ptr_aligned_by_2_and_4_via_assumption'
; CHECK-NEXT: Classifying expressions for: @test_ptr_aligned_by_2_and_4_via_assumption
; CHECK-NEXT: %iv = phi ptr [ %start, %entry ], [ %iv.next, %loop ]
; CHECK-NEXT: --> {%start,+,4}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: --> {%start,+,4}<%loop> U: [0,-1) S: [-9223372036854775808,9223372036854775807) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.next = getelementptr i8, ptr %iv, i64 4
; CHECK-NEXT: --> {(4 + %start),+,4}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: --> {(4 + %start),+,4}<%loop> U: [0,-1) S: [-9223372036854775808,9223372036854775807) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: Determining loop execution counts for: @test_ptr_aligned_by_2_and_4_via_assumption
; 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 %loop: Predicated backedge-taken count is ((-4 + (-1 * (ptrtoint ptr %start to i64)) + (ptrtoint ptr %end to i64)) /u 4)
; CHECK-NEXT: Predicates:
; CHECK-NEXT: Equal predicate: (zext i2 ((trunc i64 (ptrtoint ptr %end to i64) to i2) + (-1 * (trunc i64 (ptrtoint ptr %start to i64) to i2))) to i64) == 0
; CHECK-NEXT: Equal predicate: (zext i2 (-1 * (trunc i64 (ptrtoint ptr %start to i64) to i2)) to i64) == 0
; CHECK-NEXT: Loop %loop: Predicated constant max backedge-taken count is i64 4611686018427387903
; CHECK-NEXT: Predicates:
; CHECK-NEXT: Equal predicate: (zext i2 ((trunc i64 (ptrtoint ptr %end to i64) to i2) + (-1 * (trunc i64 (ptrtoint ptr %start to i64) to i2))) to i64) == 0
; CHECK-NEXT: Equal predicate: (zext i2 (-1 * (trunc i64 (ptrtoint ptr %start to i64) to i2)) to i64) == 0
; CHECK-NEXT: Loop %loop: Predicated symbolic max backedge-taken count is ((-4 + (-1 * (ptrtoint ptr %start to i64)) + (ptrtoint ptr %end to i64)) /u 4)
; CHECK-NEXT: Predicates:
; CHECK-NEXT: Equal predicate: (zext i2 ((trunc i64 (ptrtoint ptr %end to i64) to i2) + (-1 * (trunc i64 (ptrtoint ptr %start to i64) to i2))) to i64) == 0
; CHECK-NEXT: Equal predicate: (zext i2 (-1 * (trunc i64 (ptrtoint ptr %start to i64) to i2)) to i64) == 0
;
entry:
call void @llvm.assume(i1 true) [ "align"(ptr %start, i64 2) ]
Expand All @@ -615,9 +615,9 @@ define void @test_ptrs_aligned_by_4_via_assumption(ptr %start, ptr %end) {
; CHECK-LABEL: 'test_ptrs_aligned_by_4_via_assumption'
; CHECK-NEXT: Classifying expressions for: @test_ptrs_aligned_by_4_via_assumption
; CHECK-NEXT: %iv = phi ptr [ %start, %entry ], [ %iv.next, %loop ]
; CHECK-NEXT: --> {%start,+,4}<%loop> U: full-set S: full-set Exits: ((4 * ((-4 + (-1 * (ptrtoint ptr %start to i64)) + (ptrtoint ptr %end to i64)) /u 4))<nuw> + %start) LoopDispositions: { %loop: Computable }
; CHECK-NEXT: --> {%start,+,4}<%loop> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: (-4 + (-1 * (ptrtoint ptr %start to i64)) + (ptrtoint ptr %end to i64) + %start) LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.next = getelementptr i8, ptr %iv, i64 4
; CHECK-NEXT: --> {(4 + %start),+,4}<%loop> U: full-set S: full-set Exits: (4 + (4 * ((-4 + (-1 * (ptrtoint ptr %start to i64)) + (ptrtoint ptr %end to i64)) /u 4))<nuw> + %start) LoopDispositions: { %loop: Computable }
; CHECK-NEXT: --> {(4 + %start),+,4}<%loop> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: ((-1 * (ptrtoint ptr %start to i64)) + (ptrtoint ptr %end to i64) + %start) LoopDispositions: { %loop: Computable }
; CHECK-NEXT: Determining loop execution counts for: @test_ptrs_aligned_by_4_via_assumption
; CHECK-NEXT: Loop %loop: backedge-taken count is ((-4 + (-1 * (ptrtoint ptr %start to i64)) + (ptrtoint ptr %end to i64)) /u 4)
; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 4611686018427387903
Expand All @@ -644,9 +644,9 @@ define void @test_ptrs_aligned_by_8_via_assumption(ptr %start, ptr %end) {
; CHECK-LABEL: 'test_ptrs_aligned_by_8_via_assumption'
; CHECK-NEXT: Classifying expressions for: @test_ptrs_aligned_by_8_via_assumption
; CHECK-NEXT: %iv = phi ptr [ %start, %entry ], [ %iv.next, %loop ]
; CHECK-NEXT: --> {%start,+,4}<%loop> U: full-set S: full-set Exits: ((4 * ((-4 + (-1 * (ptrtoint ptr %start to i64)) + (ptrtoint ptr %end to i64)) /u 4))<nuw> + %start) LoopDispositions: { %loop: Computable }
; CHECK-NEXT: --> {%start,+,4}<%loop> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: (-4 + (-1 * (ptrtoint ptr %start to i64)) + (ptrtoint ptr %end to i64) + %start) LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.next = getelementptr i8, ptr %iv, i64 4
; CHECK-NEXT: --> {(4 + %start),+,4}<%loop> U: full-set S: full-set Exits: (4 + (4 * ((-4 + (-1 * (ptrtoint ptr %start to i64)) + (ptrtoint ptr %end to i64)) /u 4))<nuw> + %start) LoopDispositions: { %loop: Computable }
; CHECK-NEXT: --> {(4 + %start)<nuw><nsw>,+,4}<%loop> U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: ((-1 * (ptrtoint ptr %start to i64)) + (ptrtoint ptr %end to i64) + %start) LoopDispositions: { %loop: Computable }
; CHECK-NEXT: Determining loop execution counts for: @test_ptrs_aligned_by_8_via_assumption
; CHECK-NEXT: Loop %loop: backedge-taken count is ((-4 + (-1 * (ptrtoint ptr %start to i64)) + (ptrtoint ptr %end to i64)) /u 4)
; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 4611686018427387903
Expand Down Expand Up @@ -677,22 +677,22 @@ define void @test_ptr_aligned_by_4_via_assumption_multiple_loop_predecessors(ptr
; CHECK-NEXT: %c = call i1 @cond()
; CHECK-NEXT: --> %c U: full-set S: full-set
; CHECK-NEXT: %iv = phi ptr [ %start, %then ], [ %start, %else ], [ %iv.next, %loop ]
; CHECK-NEXT: --> {%start,+,4}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: --> {%start,+,4}<%loop> U: [0,-1) S: [-9223372036854775808,9223372036854775807) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.next = getelementptr i8, ptr %iv, i64 4
; CHECK-NEXT: --> {(4 + %start),+,4}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: --> {(4 + %start),+,4}<%loop> U: [0,-1) S: [-9223372036854775808,9223372036854775807) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: Determining loop execution counts for: @test_ptr_aligned_by_4_via_assumption_multiple_loop_predecessors
; 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 %loop: Predicated backedge-taken count is ((-4 + (-1 * (ptrtoint ptr %start to i64)) + (ptrtoint ptr %end to i64)) /u 4)
; CHECK-NEXT: Predicates:
; CHECK-NEXT: Equal predicate: (zext i2 ((trunc i64 (ptrtoint ptr %end to i64) to i2) + (-1 * (trunc i64 (ptrtoint ptr %start to i64) to i2))) to i64) == 0
; CHECK-NEXT: Equal predicate: (zext i2 (-1 * (trunc i64 (ptrtoint ptr %start to i64) to i2)) to i64) == 0
; CHECK-NEXT: Loop %loop: Predicated constant max backedge-taken count is i64 4611686018427387903
; CHECK-NEXT: Predicates:
; CHECK-NEXT: Equal predicate: (zext i2 ((trunc i64 (ptrtoint ptr %end to i64) to i2) + (-1 * (trunc i64 (ptrtoint ptr %start to i64) to i2))) to i64) == 0
; CHECK-NEXT: Equal predicate: (zext i2 (-1 * (trunc i64 (ptrtoint ptr %start to i64) to i2)) to i64) == 0
; CHECK-NEXT: Loop %loop: Predicated symbolic max backedge-taken count is ((-4 + (-1 * (ptrtoint ptr %start to i64)) + (ptrtoint ptr %end to i64)) /u 4)
; CHECK-NEXT: Predicates:
; CHECK-NEXT: Equal predicate: (zext i2 ((trunc i64 (ptrtoint ptr %end to i64) to i2) + (-1 * (trunc i64 (ptrtoint ptr %start to i64) to i2))) to i64) == 0
; CHECK-NEXT: Equal predicate: (zext i2 (-1 * (trunc i64 (ptrtoint ptr %start to i64) to i2)) to i64) == 0
;
entry:
call void @llvm.assume(i1 true) [ "align"(ptr %start, i64 2) ]
Expand Down
Loading