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[LoopPeel] Support last iteration peeling of min/max intrinsics #143598

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Merged
merged 1 commit into from
Jun 17, 2025
Merged

[LoopPeel] Support last iteration peeling of min/max intrinsics #143598

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5 changes: 4 additions & 1 deletion llvm/lib/Transforms/Utils/LoopPeel.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -545,8 +545,11 @@ countToEliminateCompares(Loop &L, unsigned MaxPeelCount, ScalarEvolution &SE,
const SCEV *IterVal = AddRec->evaluateAtIteration(
SE.getConstant(AddRec->getType(), NewPeelCount), SE);
if (!PeelWhilePredicateIsKnown(NewPeelCount, IterVal, BoundSCEV, Step,
Pred))
Pred)) {
if (shouldPeelLastIteration(L, Pred, AddRec, BoundSCEV, SE, TTI))
DesiredPeelCountLast = 1;
return;
}
DesiredPeelCount = NewPeelCount;
};

Expand Down
48 changes: 38 additions & 10 deletions llvm/test/Transforms/LoopUnroll/peel-last-iteration-minmax.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -41,16 +41,27 @@ define i32 @smin_unit_step() {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: br label %[[LOOP:.*]]
; CHECK: [[LOOP]]:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[IV_NEXT:%.*]], %[[LOOP]] ]
; CHECK-NEXT: [[IV1:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[IV_NEXT1:%.*]], %[[LOOP]] ]
; CHECK-NEXT: call void @foo(i32 1)
; CHECK-NEXT: [[IV_NEXT1]] = add nuw nsw i32 [[IV1]], 1
; CHECK-NEXT: [[EC:%.*]] = icmp ne i32 [[IV_NEXT1]], 1023
; CHECK-NEXT: br i1 [[EC]], label %[[LOOP]], label %[[EXIT_PEEL_BEGIN:.*]], !llvm.loop [[LOOP0:![0-9]+]]
; CHECK: [[EXIT_PEEL_BEGIN]]:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ [[IV_NEXT1]], %[[LOOP]] ]
; CHECK-NEXT: br label %[[LOOP_PEEL:.*]]
; CHECK: [[LOOP_PEEL]]:
; CHECK-NEXT: [[SUB:%.*]] = sub i32 1024, [[IV]]
; CHECK-NEXT: [[MINMAX:%.*]] = call i32 @llvm.smin.i32(i32 [[SUB]], i32 1)
; CHECK-NEXT: call void @foo(i32 [[MINMAX]])
; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i32 [[IV]], 1
; CHECK-NEXT: [[IV_NEXT:%.*]] = add nuw nsw i32 [[IV]], 1
; CHECK-NEXT: [[EC_PEEL:%.*]] = icmp ne i32 [[IV_NEXT]], 1024
; CHECK-NEXT: br i1 [[EC_PEEL]], label %[[LOOP]], label %[[EXIT:.*]]
; CHECK-NEXT: br i1 [[EC_PEEL]], label %[[EXIT_PEEL_NEXT:.*]], label %[[EXIT_PEEL_NEXT]]
; CHECK: [[EXIT_PEEL_NEXT]]:
; CHECK-NEXT: br label %[[LOOP_PEEL_NEXT:.*]]
; CHECK: [[LOOP_PEEL_NEXT]]:
; CHECK-NEXT: br label %[[EXIT:.*]]
; CHECK: [[EXIT]]:
; CHECK-NEXT: [[MINMAX_LCSSA:%.*]] = phi i32 [ [[MINMAX]], %[[LOOP]] ]
; CHECK-NEXT: ret i32 [[MINMAX_LCSSA]]
; CHECK-NEXT: ret i32 [[MINMAX]]
;
entry:
br label %loop
Expand All @@ -74,16 +85,28 @@ define i32 @smax_unit_step() {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: br label %[[LOOP:.*]]
; CHECK: [[LOOP]]:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[IV_NEXT:%.*]], %[[LOOP]] ]
; CHECK-NEXT: [[IV1:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[IV_NEXT1:%.*]], %[[LOOP]] ]
; CHECK-NEXT: [[SUB1:%.*]] = sub nuw nsw i32 1024, [[IV1]]
; CHECK-NEXT: call void @foo(i32 [[SUB1]])
; CHECK-NEXT: [[IV_NEXT1]] = add nuw nsw i32 [[IV1]], 1
; CHECK-NEXT: [[EC:%.*]] = icmp ne i32 [[IV_NEXT1]], 1023
; CHECK-NEXT: br i1 [[EC]], label %[[LOOP]], label %[[EXIT_PEEL_BEGIN:.*]], !llvm.loop [[LOOP2:![0-9]+]]
; CHECK: [[EXIT_PEEL_BEGIN]]:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ [[IV_NEXT1]], %[[LOOP]] ]
; CHECK-NEXT: br label %[[LOOP_PEEL:.*]]
; CHECK: [[LOOP_PEEL]]:
; CHECK-NEXT: [[SUB:%.*]] = sub i32 1024, [[IV]]
; CHECK-NEXT: [[MINMAX:%.*]] = call i32 @llvm.smax.i32(i32 [[SUB]], i32 1)
; CHECK-NEXT: call void @foo(i32 [[MINMAX]])
; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i32 [[IV]], 1
; CHECK-NEXT: [[IV_NEXT:%.*]] = add nuw nsw i32 [[IV]], 1
; CHECK-NEXT: [[EC_PEEL:%.*]] = icmp ne i32 [[IV_NEXT]], 1024
; CHECK-NEXT: br i1 [[EC_PEEL]], label %[[LOOP]], label %[[EXIT:.*]]
; CHECK-NEXT: br i1 [[EC_PEEL]], label %[[EXIT_PEEL_NEXT:.*]], label %[[EXIT_PEEL_NEXT]]
; CHECK: [[EXIT_PEEL_NEXT]]:
; CHECK-NEXT: br label %[[LOOP_PEEL_NEXT:.*]]
; CHECK: [[LOOP_PEEL_NEXT]]:
; CHECK-NEXT: br label %[[EXIT:.*]]
; CHECK: [[EXIT]]:
; CHECK-NEXT: [[MINMAX_LCSSA:%.*]] = phi i32 [ [[MINMAX]], %[[LOOP]] ]
; CHECK-NEXT: ret i32 [[MINMAX_LCSSA]]
; CHECK-NEXT: ret i32 [[MINMAX]]
;
entry:
br label %loop
Expand Down Expand Up @@ -135,3 +158,8 @@ exit:
ret i32 %minmax.lcssa
}

;.
; CHECK: [[LOOP0]] = distinct !{[[LOOP0]], [[META1:![0-9]+]]}
; CHECK: [[META1]] = !{!"llvm.loop.peeled.count", i32 1}
; CHECK: [[LOOP2]] = distinct !{[[LOOP2]], [[META1]]}
;.
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