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[ValueTracking] Infer X u<= X +nuw Y for any Y #75524

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Merged
merged 3 commits into from
Dec 15, 2023
Merged

[ValueTracking] Infer X u<= X +nuw Y for any Y #75524

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41b120e
[ValueTracking] Add pre-commit tests from PR70374. NFC.
dtcxzyw Dec 14, 2023
c29fa5a
[ValueTracking] Infer `X u<= X +nuw Y` for any Y
dtcxzyw Dec 14, 2023
310fdf2
[ValueTracking] Add a commuted add test. NFC.
dtcxzyw Dec 15, 2023
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7 changes: 3 additions & 4 deletions llvm/lib/Analysis/ValueTracking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8102,10 +8102,9 @@ static bool isTruePredicate(CmpInst::Predicate Pred, const Value *LHS,
}

case CmpInst::ICMP_ULE: {
const APInt *C;

// LHS u<= LHS +_{nuw} C for any C
if (match(RHS, m_NUWAdd(m_Specific(LHS), m_APInt(C))))
// LHS u<= LHS +_{nuw} V for any V
if (match(RHS, m_c_Add(m_Specific(LHS), m_Value())) &&
cast<OverflowingBinaryOperator>(RHS)->hasNoUnsignedWrap())
return true;

// RHS >> V u<= RHS for any V
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38 changes: 38 additions & 0 deletions llvm/test/Transforms/InstSimplify/implies.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -316,6 +316,44 @@ define i1 @test_uge_icmp(i32 %length.i, i32 %i) {
ret i1 %res
}

; Test from PR70374
define i1 @pr70374(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @pr70374(
; CHECK-NEXT: [[ADD:%.*]] = add nuw i32 [[Y:%.*]], [[Z:%.*]]
; CHECK-NEXT: [[CMP1:%.*]] = icmp ule i32 [[ADD]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[CMP1]]
;
%add = add nuw i32 %y, %z
%cmp1 = icmp ule i32 %add, %x
%cmp2 = icmp uge i32 %x, %y
%res = and i1 %cmp2, %cmp1
ret i1 %res
}

define i1 @pr70374_commuted_add(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @pr70374_commuted_add(
; CHECK-NEXT: [[ADD:%.*]] = add nuw i32 [[Z:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[CMP1:%.*]] = icmp ule i32 [[ADD]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[CMP1]]
;
%add = add nuw i32 %z, %y
%cmp1 = icmp ule i32 %add, %x
%cmp2 = icmp uge i32 %x, %y
%res = and i1 %cmp2, %cmp1
ret i1 %res
}

define i1 @test_uge_icmp_value(i32 %length.i, i32 %i, i32 %j) {
; CHECK-LABEL: @test_uge_icmp_value(
; CHECK-NEXT: ret i1 true
;
%iplusj = add nuw i32 %i, %j
%var29 = icmp uge i32 %length.i, %i
%var30 = icmp uge i32 %length.i, %iplusj
%res = icmp ule i1 %var30, %var29
ret i1 %res
}

; negative case, X + 1 <(s) Y !==> X <(s) Y (X = 0x7fffffff, Y = 0x7fbfffff)
define i1 @test_sgt_icmp_no_nsw(i32 %length.i, i32 %i) {
; CHECK-LABEL: @test_sgt_icmp_no_nsw(
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