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[IndVarSimplify] Drop samesign flags after narrowing compares #116263

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Merged
merged 2 commits into from
Nov 15, 2024
Merged

[IndVarSimplify] Drop samesign flags after narrowing compares #116263

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064bfdd
[IndVarSimplify] Add pre-commit tests. NFC.
dtcxzyw Nov 14, 2024
2f587c3
[IndVarSimplify] Drop samesame flags after narrowing compares
dtcxzyw Nov 14, 2024
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2 changes: 2 additions & 0 deletions llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1530,6 +1530,8 @@ bool IndVarSimplify::canonicalizeExitCondition(Loop *L) {
L->getLoopPreheader()->getTerminator()->getIterator());
ICmp->setOperand(Swapped ? 1 : 0, LHSOp);
ICmp->setOperand(Swapped ? 0 : 1, NewRHS);
// Samesign flag cannot be preserved after narrowing the compare.
ICmp->setSameSign(false);
if (LHS->use_empty())
DeadInsts.push_back(LHS);
};
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40 changes: 40 additions & 0 deletions llvm/test/Transforms/IndVarSimplify/finite-exit-comparisons.ll
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Expand Up @@ -1052,3 +1052,43 @@ for.end: ; preds = %for.body, %entry
ret void
}

define i8 @test_drop_icmp_samesign(i1 %cond, i32 range(i32 0, 32) %x) {
; CHECK-LABEL: @test_drop_icmp_samesign(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[COND:%.*]], label [[FOR_BODY_PREHEADER:%.*]], label [[ELSE:%.*]]
; CHECK: for.body.preheader:
; CHECK-NEXT: [[TMP0:%.*]] = trunc i32 [[X:%.*]] to i8
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: else:
; CHECK-NEXT: [[CALL1:%.*]] = call i8 @callee()
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[CALL2:%.*]] = call i8 @callee()
; CHECK-NEXT: [[COND2:%.*]] = icmp ugt i8 [[TMP0]], [[CALL2]]
; CHECK-NEXT: br i1 [[COND2]], label [[FOR_BODY]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK: exit.loopexit:
; CHECK-NEXT: [[CALL2_LCSSA:%.*]] = phi i8 [ [[CALL2]], [[FOR_BODY]] ]
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: [[RES:%.*]] = phi i8 [ [[CALL1]], [[ELSE]] ], [ [[CALL2_LCSSA]], [[EXIT_LOOPEXIT]] ]
; CHECK-NEXT: ret i8 [[RES]]
;
entry:
br i1 %cond, label %for.body, label %else

else:
%call1 = call i8 @callee()
br label %exit

for.body:
%call2 = call i8 @callee()
%ext = zext i8 %call2 to i32
%cond2 = icmp samesign ugt i32 %x, %ext
br i1 %cond2, label %for.body, label %exit

exit:
%res = phi i8 [ %call1, %else ], [ %call2, %for.body ]
ret i8 %res
}

declare i8 @callee()
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