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[LVI] Add support for trunc nuw range. #154021

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Merged
merged 2 commits into from
Aug 17, 2025
Merged

[LVI] Add support for trunc nuw range. #154021

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011b0df
[LVI] Add test for trunc nuw range. (NFC)
andjo403 Aug 17, 2025
5584630
[LVI] Add support for trunc nuw range.
andjo403 Aug 17, 2025
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9 changes: 7 additions & 2 deletions llvm/lib/Analysis/LazyValueInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -927,8 +927,13 @@ LazyValueInfoImpl::solveBlockValueCast(CastInst *CI, BasicBlock *BB) {
// NOTE: We're currently limited by the set of operations that ConstantRange
// can evaluate symbolically. Enhancing that set will allows us to analyze
// more definitions.
return ValueLatticeElement::getRange(LHSRange.castOp(CI->getOpcode(),
ResultBitWidth));
ConstantRange Res = ConstantRange::getEmpty(ResultBitWidth);
if (auto *Trunc = dyn_cast<TruncInst>(CI))
Res = LHSRange.truncate(ResultBitWidth, Trunc->getNoWrapKind());
else
Res = LHSRange.castOp(CI->getOpcode(), ResultBitWidth);

return ValueLatticeElement::getRange(Res);
}

std::optional<ValueLatticeElement>
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40 changes: 40 additions & 0 deletions llvm/test/Transforms/CorrelatedValuePropagation/trunc.ll
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Expand Up @@ -106,3 +106,43 @@ define i1 @overdefined_range_negative(i8 %A, i8 %B) {
%trunc = trunc i8 %xor to i1
ret i1 %trunc
}

define i1 @trunc_nuw_infere_false_for_icmp_ne_1(i8 %x) {
; CHECK-LABEL: define i1 @trunc_nuw_infere_false_for_icmp_ne_1(
; CHECK-SAME: i8 [[X:%.*]]) {
; CHECK-NEXT: [[ICMP:%.*]] = icmp ne i8 [[X]], 1
; CHECK-NEXT: br i1 [[ICMP]], label %[[IFTRUE:.*]], label %[[IFFALSE:.*]]
; CHECK: [[IFTRUE]]:
; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw i8 [[X]] to i1
; CHECK-NEXT: ret i1 false
; CHECK: [[IFFALSE]]:
; CHECK-NEXT: ret i1 true
;
%icmp = icmp ne i8 %x, 1
br i1 %icmp, label %iftrue, label %iffalse
iftrue:
%trunc = trunc nuw i8 %x to i1
ret i1 %trunc
iffalse:
ret i1 true
}

define i1 @neg_trunc_do_not_infere_false_for_icmp_ne_1(i8 %x) {
; CHECK-LABEL: define i1 @neg_trunc_do_not_infere_false_for_icmp_ne_1(
; CHECK-SAME: i8 [[X:%.*]]) {
; CHECK-NEXT: [[ICMP:%.*]] = icmp ne i8 [[X]], 1
; CHECK-NEXT: br i1 [[ICMP]], label %[[IFTRUE:.*]], label %[[IFFALSE:.*]]
; CHECK: [[IFTRUE]]:
; CHECK-NEXT: [[TRUNC:%.*]] = trunc i8 [[X]] to i1
; CHECK-NEXT: ret i1 [[TRUNC]]
; CHECK: [[IFFALSE]]:
; CHECK-NEXT: ret i1 true
;
%icmp = icmp ne i8 %x, 1
br i1 %icmp, label %iftrue, label %iffalse
iftrue:
%trunc = trunc i8 %x to i1
ret i1 %trunc
iffalse:
ret i1 true
}