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[LoopPeel] Handle non-local instructions/arguments when updating exiting values #142993

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Merged
dtcxzyw merged 2 commits into from
Jun 6, 2025
Merged

[LoopPeel] Handle non-local instructions/arguments when updating exiting values #142993

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d057a97
[LoopPeel] Handle non-local instructions/arguments when updating exit…
dtcxzyw Jun 5, 2025
e1c5475
[LoopPeel] Update tests. NFC.
dtcxzyw Jun 5, 2025
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6 changes: 5 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 @@ -1257,7 +1257,11 @@ bool llvm::peelLoop(Loop *L, unsigned PeelCount, bool PeelLast, LoopInfo *LI,
// Now adjust users of the original exit values by replacing them with the
// exit value from the peeled iteration and remove them.
for (const auto &[P, E] : ExitValues) {
P->replaceAllUsesWith(isa<Constant>(E) ? E : &*VMap.lookup(E));
Instruction *ExitInst = dyn_cast<Instruction>(E);
if (ExitInst && L->contains(ExitInst))
P->replaceAllUsesWith(&*VMap[ExitInst]);
else
P->replaceAllUsesWith(E);
P->eraseFromParent();
}
formLCSSA(*L, DT, LI, SE);
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98 changes: 98 additions & 0 deletions llvm/test/Transforms/LoopUnroll/unroll-and-peel-last-iteration.ll
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Expand Up @@ -71,8 +71,106 @@ exit:
ret i32 %1
}

; Test case for https://github.com/llvm/llvm-project/issues/142895.

define i32 @pr142895_exit_value_is_arg(i32 %arg) {
; CHECK-LABEL: define i32 @pr142895_exit_value_is_arg(
; CHECK-SAME: i32 [[ARG:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: br label %[[LOOP:.*]]
; CHECK: [[LOOP]]:
; CHECK-NEXT: [[INDVAR:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[INC:%.*]], %[[LOOP]] ]
; CHECK-NEXT: [[INC]] = add nuw nsw i32 [[INDVAR]], 1
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i32 [[INC]], 32
; CHECK-NEXT: br i1 [[EXITCOND]], label %[[LOOP]], label %[[EXIT_PEEL_BEGIN:.*]], !llvm.loop [[LOOP2:![0-9]+]]
; CHECK: [[EXIT_PEEL_BEGIN]]:
; CHECK-NEXT: [[TMP0:%.*]] = phi i32 [ [[INC]], %[[LOOP]] ]
; CHECK-NEXT: br label %[[LOOP_PEEL:.*]]
; CHECK: [[LOOP_PEEL]]:
; CHECK-NEXT: [[CMP1_PEEL:%.*]] = icmp eq i32 [[TMP0]], 32
; CHECK-NEXT: [[SEL_PEEL:%.*]] = select i1 [[CMP1_PEEL]], i32 0, i32 0
; CHECK-NEXT: [[SUB_PEEL:%.*]] = sub i32 0, 0
; CHECK-NEXT: [[XOR_PEEL:%.*]] = xor i32 0, 0
; CHECK-NEXT: [[INC_PEEL:%.*]] = add i32 [[TMP0]], 1
; CHECK-NEXT: [[EXITCOND_PEEL:%.*]] = icmp ne i32 [[INC_PEEL]], 33
; CHECK-NEXT: br i1 [[EXITCOND_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: ret i32 [[ARG]]
;
entry:
br label %loop

loop:
%indvar = phi i32 [ 0, %entry ], [ %inc, %loop ]
%cmp1 = icmp eq i32 %indvar, 32
%sel = select i1 %cmp1, i32 0, i32 0
%sub = sub i32 0, 0
%xor = xor i32 0, 0
%inc = add i32 %indvar, 1
%exitcond = icmp ne i32 %inc, 33
br i1 %exitcond, label %loop, label %exit

exit:
%exit.lcssa = phi i32 [ %arg, %loop ]
ret i32 %exit.lcssa
}

define i32 @pr142895_exit_value_is_inst(i32 %arg) {
; CHECK-LABEL: define i32 @pr142895_exit_value_is_inst(
; CHECK-SAME: i32 [[ARG:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: [[MUL:%.*]] = mul i32 [[ARG]], 7
; CHECK-NEXT: br label %[[LOOP:.*]]
; CHECK: [[LOOP]]:
; CHECK-NEXT: [[INDVAR:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[INC:%.*]], %[[LOOP]] ]
; CHECK-NEXT: [[INC]] = add nuw nsw i32 [[INDVAR]], 1
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i32 [[INC]], 32
; CHECK-NEXT: br i1 [[EXITCOND]], label %[[LOOP]], label %[[EXIT_PEEL_BEGIN:.*]], !llvm.loop [[LOOP3:![0-9]+]]
; CHECK: [[EXIT_PEEL_BEGIN]]:
; CHECK-NEXT: [[TMP0:%.*]] = phi i32 [ [[INC]], %[[LOOP]] ]
; CHECK-NEXT: br label %[[LOOP_PEEL:.*]]
; CHECK: [[LOOP_PEEL]]:
; CHECK-NEXT: [[CMP1_PEEL:%.*]] = icmp eq i32 [[TMP0]], 32
; CHECK-NEXT: [[SEL_PEEL:%.*]] = select i1 [[CMP1_PEEL]], i32 0, i32 0
; CHECK-NEXT: [[SUB_PEEL:%.*]] = sub i32 0, 0
; CHECK-NEXT: [[XOR_PEEL:%.*]] = xor i32 0, 0
; CHECK-NEXT: [[INC_PEEL:%.*]] = add i32 [[TMP0]], 1
; CHECK-NEXT: [[EXITCOND_PEEL:%.*]] = icmp ne i32 [[INC_PEEL]], 33
; CHECK-NEXT: br i1 [[EXITCOND_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: ret i32 [[MUL]]
;
entry:
%mul = mul i32 %arg, 7
br label %loop

loop:
%indvar = phi i32 [ 0, %entry ], [ %inc, %loop ]
%cmp1 = icmp eq i32 %indvar, 32
%sel = select i1 %cmp1, i32 0, i32 0
%sub = sub i32 0, 0
%xor = xor i32 0, 0
%inc = add i32 %indvar, 1
%exitcond = icmp ne i32 %inc, 33
br i1 %exitcond, label %loop, label %exit

exit:
%exit.lcssa = phi i32 [ %mul, %loop ]
ret i32 %exit.lcssa
}

declare void @foo(i32)
;.
; 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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