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[LoopUnroll][NFCI] Clean up remainder followup metadata handling #165272

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Merged
merged 2 commits into from
Oct 30, 2025
Merged

[LoopUnroll][NFCI] Clean up remainder followup metadata handling #165272

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7263e8e
[LoopUnroll][NFC] Clean up remainder followup metadata handling
jdenny-ornl Oct 27, 2025
964bb35
Merge branch 'main' into unroll-cleanup-remainder-followup
jdenny-ornl Oct 29, 2025
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19 changes: 2 additions & 17 deletions llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -460,25 +460,10 @@ CloneLoopBlocks(Loop *L, Value *NewIter, const bool UseEpilogRemainder,

Loop *NewLoop = NewLoops[L];
assert(NewLoop && "L should have been cloned");
MDNode *LoopID = NewLoop->getLoopID();

// Only add loop metadata if the loop is not going to be completely
// unrolled.
if (UnrollRemainder)
return NewLoop;

std::optional<MDNode *> NewLoopID = makeFollowupLoopID(
LoopID, {LLVMLoopUnrollFollowupAll, LLVMLoopUnrollFollowupRemainder});
if (NewLoopID) {
NewLoop->setLoopID(*NewLoopID);

// Do not setLoopAlreadyUnrolled if loop attributes have been defined
// explicitly.
return NewLoop;
}

// Add unroll disable metadata to disable future unrolling for this loop.
NewLoop->setLoopAlreadyUnrolled();
if (!UnrollRemainder)
NewLoop->setLoopAlreadyUnrolled();
return NewLoop;
}

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35 changes: 25 additions & 10 deletions llvm/test/Transforms/LoopUnroll/followup.ll
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Original file line number Diff line number Diff line change
@@ -1,9 +1,20 @@
; RUN: opt < %s -S -passes=loop-unroll -unroll-count=2 | FileCheck %s -check-prefixes=COUNT,COMMON
; RUN: opt < %s -S -passes=loop-unroll -unroll-runtime=true -unroll-runtime-epilog=true | FileCheck %s -check-prefixes=EPILOG,COMMON
; RUN: opt < %s -S -passes=loop-unroll -unroll-runtime=true -unroll-runtime-epilog=false | FileCheck %s -check-prefixes=PROLOG,COMMON
;
; Check that followup-attributes are applied after LoopUnroll.
; Check that followup attributes are applied after LoopUnroll.
;
; We choose -unroll-count=3 because it produces partial unrolling of remainder
; loops. Complete unrolling would leave no remainder loop to which to copy
; followup attributes.

; DEFINE: %{unroll} = opt < %s -S -passes=loop-unroll -unroll-count=3
; DEFINE: %{epilog} = %{unroll} -unroll-runtime -unroll-runtime-epilog=true
; DEFINE: %{prolog} = %{unroll} -unroll-runtime -unroll-runtime-epilog=false
; DEFINE: %{fc} = FileCheck %s -check-prefixes

; RUN: %{unroll} | %{fc} COMMON,COUNT
; RUN: %{epilog} | %{fc} COMMON,EPILOG,EPILOG-NO-UNROLL
; RUN: %{prolog} | %{fc} COMMON,PROLOG,PROLOG-NO-UNROLL
; RUN: %{epilog} -unroll-remainder | %{fc} COMMON,EPILOG,EPILOG-UNROLL
; RUN: %{prolog} -unroll-remainder | %{fc} COMMON,PROLOG,PROLOG-UNROLL

target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"

define i32 @test(ptr nocapture %a, i32 %n) nounwind uwtable readonly {
Expand Down Expand Up @@ -36,15 +47,17 @@ for.end: ; preds = %for.body, %entry
; COMMON-LABEL: @test(


; COUNT: br i1 %exitcond.1, label %for.end.loopexit, label %for.body, !llvm.loop ![[LOOP:[0-9]+]]
; COUNT: br i1 %exitcond.2, label %for.end.loopexit, label %for.body, !llvm.loop ![[LOOP:[0-9]+]]

; COUNT: ![[FOLLOWUP_ALL:[0-9]+]] = !{!"FollowupAll"}
; COUNT: ![[FOLLOWUP_UNROLLED:[0-9]+]] = !{!"FollowupUnrolled"}
; COUNT: ![[LOOP]] = distinct !{![[LOOP]], ![[FOLLOWUP_ALL]], ![[FOLLOWUP_UNROLLED]]}


; EPILOG: br i1 %niter.ncmp.7, label %for.end.loopexit.unr-lcssa, label %for.body, !llvm.loop ![[LOOP_0:[0-9]+]]
; EPILOG: br i1 %epil.iter.cmp, label %for.body.epil, label %for.end.loopexit.epilog-lcssa, !llvm.loop ![[LOOP_2:[0-9]+]]
; EPILOG: br i1 %niter.ncmp.2, label %for.end.loopexit.unr-lcssa, label %for.body, !llvm.loop ![[LOOP_0:[0-9]+]]
; EPILOG-NO-UNROLL: br i1 %epil.iter.cmp, label %for.body.epil, label %for.end.loopexit.epilog-lcssa, !llvm.loop ![[LOOP_2:[0-9]+]]
; EPILOG-UNROLL: br i1 %epil.iter.cmp, label %for.body.epil.1, label %for.end.loopexit.epilog-lcssa
; EPILOG-UNROLL: br i1 %epil.iter.cmp.1, label %for.body.epil, label %for.end.loopexit.epilog-lcssa, !llvm.loop ![[LOOP_2:[0-9]+]]

; EPILOG: ![[LOOP_0]] = distinct !{![[LOOP_0]], ![[FOLLOWUP_ALL:[0-9]+]], ![[FOLLOWUP_UNROLLED:[0-9]+]]}
; EPILOG: ![[FOLLOWUP_ALL]] = !{!"FollowupAll"}
Expand All @@ -53,8 +66,10 @@ for.end: ; preds = %for.body, %entry
; EPILOG: ![[FOLLOWUP_REMAINDER]] = !{!"FollowupRemainder"}


; PROLOG: br i1 %prol.iter.cmp, label %for.body.prol, label %for.body.prol.loopexit.unr-lcssa, !llvm.loop ![[LOOP_0:[0-9]+]]
; PROLOG: br i1 %exitcond.7, label %for.end.loopexit.unr-lcssa, label %for.body, !llvm.loop ![[LOOP_2:[0-9]+]]
; PROLOG-UNROLL: br i1 %prol.iter.cmp, label %for.body.prol.1, label %for.body.prol.loopexit.unr-lcssa
; PROLOG-UNROLL: br i1 %prol.iter.cmp.1, label %for.body.prol, label %for.body.prol.loopexit.unr-lcssa, !llvm.loop ![[LOOP_0:[0-9]+]]
; PROLOG-NO-UNROLL: br i1 %prol.iter.cmp, label %for.body.prol, label %for.body.prol.loopexit.unr-lcssa, !llvm.loop ![[LOOP_0:[0-9]+]]
; PROLOG: br i1 %exitcond.2, label %for.end.loopexit.unr-lcssa, label %for.body, !llvm.loop ![[LOOP_2:[0-9]+]]

; PROLOG: ![[LOOP_0]] = distinct !{![[LOOP_0]], ![[FOLLOWUP_ALL:[0-9]+]], ![[FOLLOWUP_REMAINDER:[0-9]+]]}
; PROLOG: ![[FOLLOWUP_ALL]] = !{!"FollowupAll"}
Expand Down