Thanks to visit codestin.com
Credit goes to github.com

Skip to content

[LoopInterchange] Ignore the cost-model, force interchange if legal #148858

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
sjoerdmeijer merged 10 commits into from
Jul 18, 2025
Merged

[LoopInterchange] Ignore the cost-model, force interchange if legal #148858

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
10 commits
Select commit Hold shift + click to select a range
db9c37e
[LoopInterchange] Ignore the cost-model, force interchange if legal
sjoerdmeijer Jul 15, 2025
fe979ea
Add an ignore value to the existing profitability option.
sjoerdmeijer Jul 16, 2025
5bb2158
Remove the old option, we don't need that anymore, left it accidentally
sjoerdmeijer Jul 17, 2025
1e8e667
Fix formatting.
sjoerdmeijer Jul 17, 2025
6a3b3f0
Update llvm/test/Transforms/LoopInterchange/force-interchange.ll
sjoerdmeijer Jul 17, 2025
82a3043
Addressed review comments
sjoerdmeijer Jul 17, 2025
58a6efb
Debug message when ignore has no effect.
sjoerdmeijer Jul 17, 2025
057d32b
noDuplicateRulesAndIgnore: assert that ignore doesn't appear in a list.
sjoerdmeijer Jul 18, 2025
b5bc6d1
Renamed test case labels and variables.
sjoerdmeijer Jul 18, 2025
1736f1f
Added llvm_unreachable
sjoerdmeijer Jul 18, 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
Next Next commit
[LoopInterchange] Ignore the cost-model, force interchange if legal 
This is useful for testing purposes, to get more test coverage.
  • Loading branch information
@sjoerdmeijer
sjoerdmeijer committed Jul 15, 2025
commit db9c37e08f5fbb4458ea87f539eae41c275a8a2e
7 changes: 6 additions & 1 deletion llvm/lib/Transforms/Scalar/LoopInterchange.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,10 @@ static cl::opt<unsigned int> MaxMemInstrCount(
"in the dependency matrix. Higher value may lead to more interchanges "
"at the cost of compile-time"));

static cl::opt<bool> ForceLoopInterchange(
"loop-interchange-force", cl::init(false), cl::Hidden,
cl::desc("Ignore the cost model, and force interchange if it is legal"));

Copy link
Copy Markdown
Contributor

@madhur13490 madhur13490 Jul 15, 2025

Choose a reason for hiding this comment

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

Would it be better if we call it -loop-interchange-ignore-cost-model? -force seems it covers wider scenarios.

namespace {

using LoopVector = SmallVector<Loop *, 8>;
Expand Down Expand Up @@ -599,7 +603,8 @@ struct LoopInterchange {
}
LLVM_DEBUG(dbgs() << "Loops are legal to interchange\n");
LoopInterchangeProfitability LIP(OuterLoop, InnerLoop, SE, ORE);
if (!LIP.isProfitable(InnerLoop, OuterLoop, InnerLoopId, OuterLoopId,
if (!ForceLoopInterchange &&
!LIP.isProfitable(InnerLoop, OuterLoop, InnerLoopId, OuterLoopId,
DependencyMatrix, CCM)) {
LLVM_DEBUG(dbgs() << "Interchanging loops not profitable.\n");
return false;
Expand Down
4 changes: 4 additions & 0 deletions llvm/test/Transforms/LoopInterchange/profitability-vectorization.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,10 @@
; RUN: -pass-remarks-output=%t -disable-output
; RUN: FileCheck -input-file %t --check-prefix=PROFIT-CACHE %s

; RUN: opt < %s -passes=loop-interchange -cache-line-size=64 \
; RUN: -pass-remarks-output=%t -disable-output -loop-interchange-force=true
; RUN: FileCheck -input-file %t --check-prefix=PROFIT-VEC %s
Copy link
Copy Markdown
Contributor

@kasuga-fj kasuga-fj Jul 15, 2025

Choose a reason for hiding this comment

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

Could you please add another test case? Interchanging the loops in this test would be beneficial in perspective of vectorizatoin (i.e., isProfitableForVectorization returns true in this case) because it makes the innermost loop vectorizable. It would be ideal to add a case where interchanging is definitely unprofitable.


; RUN: opt < %s -passes=loop-interchange -cache-line-size=64 \
; RUN: -pass-remarks-output=%t -disable-output -loop-interchange-profitabilities=vectorize,cache,instorder
; RUN: FileCheck -input-file %t --check-prefix=PROFIT-VEC %s
Expand Down
Loading