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[LoopPeel] Allow bidirection condition change for last iteration peeling #143562

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[LoopPeel] Allow bidirection condition change for last iteration peeling #143562

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14 changes: 8 additions & 6 deletions llvm/lib/Transforms/Utils/LoopPeel.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -357,9 +357,9 @@ bool llvm::canPeelLastIteration(const Loop &L, ScalarEvolution &SE) {
m_scev_AffineAddRec(m_SCEV(), m_scev_One(), m_SpecificLoop(&L)));
}

/// Returns true if the last iteration can be peeled off and the condition (Pred
/// LeftAR, RightSCEV) is known at the last iteration and the inverse condition
/// is known at the second-to-last.
/// Returns true if the last iteration can be peeled off because the known
/// monotonic condition (Pred LeftAR, RightSCEV) changes value on the last
/// iteration.
static bool shouldPeelLastIteration(Loop &L, CmpPredicate Pred,
const SCEVAddRecExpr *LeftAR,
const SCEV *RightSCEV, ScalarEvolution &SE,
Expand All @@ -378,9 +378,11 @@ static bool shouldPeelLastIteration(Loop &L, CmpPredicate Pred,
const SCEV *ValAtSecondToLastIter = LeftAR->evaluateAtIteration(
SE.getMinusSCEV(BTC, SE.getOne(BTC->getType())), SE);

return SE.isKnownPredicate(ICmpInst::getInversePredicate(Pred), ValAtLastIter,
RightSCEV) &&
SE.isKnownPredicate(Pred, ValAtSecondToLastIter, RightSCEV);
CmpPredicate InvPred = ICmpInst::getInversePredicate(Pred);
return (SE.isKnownPredicate(InvPred, ValAtLastIter, RightSCEV) &&
SE.isKnownPredicate(Pred, ValAtSecondToLastIter, RightSCEV)) ||
(SE.isKnownPredicate(Pred, ValAtLastIter, RightSCEV) &&
SE.isKnownPredicate(InvPred, ValAtSecondToLastIter, RightSCEV));
}

// Return the number of iterations to peel off from the beginning and end of the
Expand Down
32 changes: 27 additions & 5 deletions llvm/test/Transforms/LoopUnroll/peel-last-iteration-with-variable-trip-count.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -139,17 +139,38 @@ define i32 @peel_last_with_trip_count_check_lcssa_phi_cmp_not_invar(i32 %n) {
; CHECK-SAME: i32 [[N:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: [[SUB:%.*]] = add i32 [[N]], -2
; CHECK-NEXT: [[TMP0:%.*]] = add i32 [[N]], -1
; CHECK-NEXT: [[TMP1:%.*]] = icmp ne i32 [[TMP0]], 0
; CHECK-NEXT: br i1 [[TMP1]], label %[[ENTRY_SPLIT:.*]], label %[[EXIT_PEEL_BEGIN:.*]]
; CHECK: [[ENTRY_SPLIT]]:
; CHECK-NEXT: br label %[[LOOP:.*]]
; CHECK: [[LOOP]]:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[IV_NEXT:%.*]], %[[LOOP]] ]
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, %[[ENTRY_SPLIT]] ], [ [[IV_NEXT1:%.*]], %[[LOOP]] ]
; CHECK-NEXT: [[C:%.*]] = icmp eq i32 [[IV]], [[SUB]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[C]], i32 1, i32 2
; CHECK-NEXT: call void @foo(i32 [[SEL]])
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: [[IV_NEXT1]] = add nuw i32 [[IV]], 1
; CHECK-NEXT: [[TMP2:%.*]] = sub i32 [[N]], 1
; CHECK-NEXT: [[EC1:%.*]] = icmp ne i32 [[IV_NEXT1]], [[TMP2]]
; CHECK-NEXT: br i1 [[EC1]], label %[[LOOP]], label %[[EXIT_PEEL_BEGIN_LOOPEXIT:.*]], !llvm.loop [[LOOP2:![0-9]+]]
; CHECK: [[EXIT_PEEL_BEGIN_LOOPEXIT]]:
; CHECK-NEXT: [[DOTPH:%.*]] = phi i32 [ [[IV_NEXT1]], %[[LOOP]] ]
; CHECK-NEXT: br label %[[EXIT_PEEL_BEGIN]]
; CHECK: [[EXIT_PEEL_BEGIN]]:
; CHECK-NEXT: [[TMP3:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[DOTPH]], %[[EXIT_PEEL_BEGIN_LOOPEXIT]] ]
; CHECK-NEXT: br label %[[LOOP_PEEL:.*]]
; CHECK: [[LOOP_PEEL]]:
; CHECK-NEXT: [[C_PEEL:%.*]] = icmp eq i32 [[TMP3]], [[SUB]]
; CHECK-NEXT: [[SEL_LCSSA:%.*]] = select i1 [[C_PEEL]], i32 1, i32 2
; CHECK-NEXT: call void @foo(i32 [[SEL_LCSSA]])
; CHECK-NEXT: [[IV_NEXT:%.*]] = add i32 [[TMP3]], 1
; CHECK-NEXT: [[EC:%.*]] = icmp ne i32 [[IV_NEXT]], [[N]]
; CHECK-NEXT: br i1 [[EC]], label %[[LOOP]], label %[[EXIT:.*]]
; CHECK-NEXT: br i1 [[EC]], 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: [[SEL_LCSSA:%.*]] = phi i32 [ [[SEL]], %[[LOOP]] ]
; CHECK-NEXT: ret i32 [[SEL_LCSSA]]
;
entry:
Expand Down Expand Up @@ -214,7 +235,7 @@ define void @peel_last_with_trip_count_check_nested_loop(i32 %n) {
; CHECK-NEXT: [[IV_NEXT1]] = add nuw i32 [[IV1]], 1
; CHECK-NEXT: [[TMP2:%.*]] = sub i32 [[N]], 1
; CHECK-NEXT: [[EXITCOND_NOT1:%.*]] = icmp eq i32 [[IV_NEXT1]], [[TMP2]]
; CHECK-NEXT: br i1 [[EXITCOND_NOT1]], label %[[OUTER_HEADER_LOOPEXIT_PEEL_BEGIN_LOOPEXIT]], label %[[INNER_HEADER]], !llvm.loop [[LOOP2:![0-9]+]]
; CHECK-NEXT: br i1 [[EXITCOND_NOT1]], label %[[OUTER_HEADER_LOOPEXIT_PEEL_BEGIN_LOOPEXIT]], label %[[INNER_HEADER]], !llvm.loop [[LOOP3:![0-9]+]]
;
entry:
%sub = add i32 %n, -1
Expand Down Expand Up @@ -242,4 +263,5 @@ inner.latch:
; CHECK: [[LOOP0]] = distinct !{[[LOOP0]], [[META1:![0-9]+]]}
; CHECK: [[META1]] = !{!"llvm.loop.peeled.count", i32 1}
; CHECK: [[LOOP2]] = distinct !{[[LOOP2]], [[META1]]}
; CHECK: [[LOOP3]] = distinct !{[[LOOP3]], [[META1]]}
;.
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