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[InstCombine] Drop samesign flags in foldLogOpOfMaskedICmps_NotAllZeros_BMask_Mixed #120373

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Merged
merged 3 commits into from
Dec 18, 2024
Merged

[InstCombine] Drop samesign flags in foldLogOpOfMaskedICmps_NotAllZeros_BMask_Mixed #120373

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0ce089b
[InstCombine] Add pre-commit tests. NFC.
dtcxzyw Dec 18, 2024
05d929e
[InstCombine] Drop samesign flags in `foldLogOpOfMaskedICmps_NotAllZe…
dtcxzyw Dec 18, 2024
32ef1af
[InstCombine] Drop samesign flags in `foldLogOpOfMaskedICmps_NotAllZe…
dtcxzyw Dec 18, 2024
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10 changes: 8 additions & 2 deletions llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -455,14 +455,20 @@ static Value *foldLogOpOfMaskedICmps_NotAllZeros_BMask_Mixed(
// RHS. For example,
// (icmp ne (A & 255), 0) & (icmp eq (A & 15), 8) -> (icmp eq (A & 15), 8).
// (icmp ne (A & 15), 0) & (icmp eq (A & 15), 8) -> (icmp eq (A & 15), 8).
if (IsSuperSetOrEqual(BCst, DCst))
if (IsSuperSetOrEqual(BCst, DCst)) {
// We can't guarantee that samesign hold after this fold.
RHS->setSameSign(false);
return RHS;
}
// Otherwise, B is a subset of D. If B and E have a common bit set,
// ie. (B & E) != 0, then LHS is subsumed by RHS. For example.
// (icmp ne (A & 12), 0) & (icmp eq (A & 15), 8) -> (icmp eq (A & 15), 8).
assert(IsSubSetOrEqual(BCst, DCst) && "Precondition due to above code");
if ((*BCst & ECst) != 0)
if ((*BCst & ECst) != 0) {
// We can't guarantee that samesign hold after this fold.
RHS->setSameSign(false);
return RHS;
}
// Otherwise, LHS and RHS contradict and the whole expression becomes false
// (or true if negated.) For example,
// (icmp ne (A & 7), 0) & (icmp eq (A & 15), 8) -> false.
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25 changes: 25 additions & 0 deletions llvm/test/Transforms/InstCombine/icmp-logical.ll
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Expand Up @@ -1900,3 +1900,28 @@ define i1 @masked_icmps_bmask_notmixed_not_subset_notoptimized(i32 %A) {
%res = and i1 %tst1, %tst2
ret i1 %res
}

define i1 @pr120361(i8 %x, i8 %y) {
; CHECK-LABEL: @pr120361(
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i8 [[X:%.*]], -1
; CHECK-NEXT: ret i1 [[CMP1]]
;
%cmp1 = icmp samesign eq i8 %x, -1
%cmp2 = icmp ne i8 %x, 0
%result = select i1 %cmp2, i1 %cmp1, i1 false
ret i1 %result
}

define i1 @pr120361_v2(i32 %x) {
; CHECK-LABEL: @pr120361_v2(
; CHECK-NEXT: [[AND2:%.*]] = and i32 [[X:%.*]], -113
; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[AND2]], 15
; CHECK-NEXT: ret i1 [[CMP2]]
;
%and1 = and i32 %x, 15
%cmp1 = icmp ne i32 %and1, 0
%and2 = and i32 %x, -113
%cmp2 = icmp samesign eq i32 %and2, 15
%and = select i1 %cmp1, i1 %cmp2, i1 false
ret i1 %and
}
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