Skip to content

[LV] Return Invalid from getLegacyCost when instruction cost forced. #154543

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 4 commits into from
Aug 26, 2025
Merged

[LV] Return Invalid from getLegacyCost when instruction cost forced. #154543

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
f1e98a6
[LV] Return Invalid from getLegacyCost when instruction cost forced.
kmclaughlin-arm Aug 20, 2025
e9ccb54
- Replace getNumOccurrences() with ForceTargetInstructionCost
kmclaughlin-arm Aug 20, 2025
4b4d4a5
- Moved new test into force-target-instruction-cost.ll
kmclaughlin-arm Aug 20, 2025
2f14b65
- Use -force-target-instruction-cost=10
kmclaughlin-arm Aug 26, 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
7 changes: 4 additions & 3 deletions llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6760,9 +6760,10 @@ void LoopVectorizationPlanner::plan(ElementCount UserVF, unsigned UserIC) {

InstructionCost VPCostContext::getLegacyCost(Instruction *UI,
ElementCount VF) const {
if (ForceTargetInstructionCost.getNumOccurrences())
return InstructionCost(ForceTargetInstructionCost.getNumOccurrences());
return CM.getInstructionCost(UI, VF);
Copy link
Contributor

@david-arm david-arm Aug 20, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This is not a fault with your patch, but it looks like it was already broken due to this:

  return InstructionCost(ForceTargetInstructionCost.getNumOccurrences());

I'm pretty sure it should be:

  return InstructionCost(ForceTargetInstructionCost);

similar to LoopVectorizationCostModel::expectedCost

Copy link
Contributor Author

@kmclaughlin-arm kmclaughlin-arm Aug 20, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I think you're right, it should be ForceTargetInstructionCost. I've updated this in the latest commit.

Copy link
Contributor

@fhahn fhahn Aug 20, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Yes, to test this we need a test that passes a large value, e.g. -force-target-instruction-cost=100 in llvm/test/Transforms/LoopVectorize/AArch64/force-target-instruction-cost.ll would do it

InstructionCost Cost = CM.getInstructionCost(UI, VF);
if (Cost.isValid() && ForceTargetInstructionCost.getNumOccurrences())
return InstructionCost(ForceTargetInstructionCost);
return Cost;
}

bool VPCostContext::isLegacyUniformAfterVectorization(Instruction *I,
Expand Down
69 changes: 63 additions & 6 deletions llvm/test/Transforms/LoopVectorize/AArch64/force-target-instruction-cost.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -p loop-vectorize -force-target-instruction-cost=1 -S %s | FileCheck %s
; RUN: opt -p loop-vectorize -force-target-instruction-cost=10 -S %s | FileCheck %s

target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128-Fn32"
target triple = "arm64-apple-macosx14.0.0"
Expand Down Expand Up @@ -65,19 +65,17 @@ define void @test_iv_cost(ptr %ptr.start, i8 %a, i64 %b) {
; CHECK-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[START]], 4
; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label %[[VEC_EPILOG_SCALAR_PH:.*]], label %[[VECTOR_MAIN_LOOP_ITER_CHECK:.*]]
; CHECK: [[VECTOR_MAIN_LOOP_ITER_CHECK]]:
; CHECK-NEXT: [[MIN_ITERS_CHECK1:%.*]] = icmp ult i64 [[START]], 32
; CHECK-NEXT: [[MIN_ITERS_CHECK1:%.*]] = icmp ult i64 [[START]], 16
; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK1]], label %[[VEC_EPILOG_PH:.*]], label %[[VECTOR_PH:.*]]
; CHECK: [[VECTOR_PH]]:
; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[START]], 32
; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[START]], 16
; CHECK-NEXT: [[N_VEC:%.*]] = sub i64 [[START]], [[N_MOD_VF]]
; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
; CHECK: [[VECTOR_BODY]]:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
; CHECK-NEXT: [[NEXT_GEP1:%.*]] = getelementptr i8, ptr [[PTR_START]], i64 [[INDEX]]
; CHECK-NEXT: [[TMP3:%.*]] = getelementptr i8, ptr [[NEXT_GEP1]], i32 16
; CHECK-NEXT: store <16 x i8> zeroinitializer, ptr [[NEXT_GEP1]], align 1
; CHECK-NEXT: store <16 x i8> zeroinitializer, ptr [[TMP3]], align 1
; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 32
; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 16
; CHECK-NEXT: [[TMP4:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
; CHECK-NEXT: br i1 [[TMP4]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP4:![0-9]+]]
; CHECK: [[MIDDLE_BLOCK]]:
Expand Down Expand Up @@ -366,6 +364,63 @@ exit:
ret void
}

define void @invalid_legacy_cost(i64 %N, ptr %x) #0 {
; CHECK-LABEL: define void @invalid_legacy_cost(
; CHECK-SAME: i64 [[N:%.*]], ptr [[X:%.*]]) #[[ATTR0:[0-9]+]] {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: [[TMP0:%.*]] = add i64 [[N]], 1
; CHECK-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[TMP0]], 2
; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label %[[SCALAR_PH:.*]], label %[[VECTOR_PH:.*]]
; CHECK: [[VECTOR_PH]]:
; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[TMP0]], 2
; CHECK-NEXT: [[N_VEC:%.*]] = sub i64 [[TMP0]], [[N_MOD_VF]]
; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
; CHECK: [[VECTOR_BODY]]:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
; CHECK-NEXT: [[TMP5:%.*]] = alloca i8, i64 0, align 16
; CHECK-NEXT: [[TMP6:%.*]] = alloca i8, i64 0, align 16
; CHECK-NEXT: [[TMP7:%.*]] = insertelement <2 x ptr> poison, ptr [[TMP5]], i32 0
; CHECK-NEXT: [[TMP8:%.*]] = insertelement <2 x ptr> [[TMP7]], ptr [[TMP6]], i32 1
; CHECK-NEXT: [[TMP9:%.*]] = getelementptr ptr, ptr [[X]], i64 [[INDEX]]
; CHECK-NEXT: store <2 x ptr> [[TMP8]], ptr [[TMP9]], align 8
; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 2
; CHECK-NEXT: [[TMP11:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
; CHECK-NEXT: br i1 [[TMP11]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP23:![0-9]+]]
; CHECK: [[MIDDLE_BLOCK]]:
; CHECK-NEXT: [[CMP_N:%.*]] = icmp eq i64 [[TMP0]], [[N_VEC]]
; CHECK-NEXT: br i1 [[CMP_N]], label %[[FOR_END:.*]], label %[[SCALAR_PH]]
; CHECK: [[SCALAR_PH]]:
; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i64 [ [[N_VEC]], %[[MIDDLE_BLOCK]] ], [ 0, %[[ENTRY]] ]
; CHECK-NEXT: br label %[[FOR_BODY:.*]]
; CHECK: [[FOR_BODY]]:
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[BC_RESUME_VAL]], %[[SCALAR_PH]] ], [ [[IV_NEXT:%.*]], %[[FOR_BODY]] ]
; CHECK-NEXT: [[TMP12:%.*]] = alloca i8, i64 0, align 16
; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr ptr, ptr [[X]], i64 [[IV]]
; CHECK-NEXT: store ptr [[TMP12]], ptr [[ARRAYIDX]], align 8
; CHECK-NEXT: [[IV_NEXT]] = add i64 [[IV]], 1
; CHECK-NEXT: [[EXITCOND_NOT:%.*]] = icmp eq i64 [[IV]], [[N]]
; CHECK-NEXT: br i1 [[EXITCOND_NOT]], label %[[FOR_END]], label %[[FOR_BODY]], !llvm.loop [[LOOP24:![0-9]+]]
; CHECK: [[FOR_END]]:
; CHECK-NEXT: ret void
;
entry:
br label %for.body

for.body:
%iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
%0 = alloca i8, i64 0, align 16
%arrayidx = getelementptr ptr, ptr %x, i64 %iv
store ptr %0, ptr %arrayidx, align 8
%iv.next = add i64 %iv, 1
%exitcond.not = icmp eq i64 %iv, %N
br i1 %exitcond.not, label %for.end, label %for.body

for.end:
ret void
}

attributes #0 = { "target-features"="+neon,+sve" vscale_range(1,16) }

declare void @llvm.assume(i1 noundef)
declare i64 @llvm.umin.i64(i64, i64)
;.
Expand All @@ -392,4 +447,6 @@ declare i64 @llvm.umin.i64(i64, i64)
; CHECK: [[META20]] = !{[[META13]]}
; CHECK: [[LOOP21]] = distinct !{[[LOOP21]], [[META1]], [[META2]]}
; CHECK: [[LOOP22]] = distinct !{[[LOOP22]], [[META1]]}
; CHECK: [[LOOP23]] = distinct !{[[LOOP23]], [[META1]], [[META2]]}
; CHECK: [[LOOP24]] = distinct !{[[LOOP24]], [[META2]], [[META1]]}
;.
Loading