[LVI] Handle implication from icmp of trunc (PR51867)

Similar to the existing urem code, if we have (trunc X) >= C,
then also X >= C.

Proof: https://alive2.llvm.org/ce/z/RF4YR2

Fixes https://github.com/llvm/llvm-project/issues/51867.
This commit is contained in:
Nikita Popov 2022-01-18 10:54:06 +01:00
parent b7bf96a258
commit 3ec7f46e99
2 changed files with 8 additions and 10 deletions

View File

@ -1132,14 +1132,16 @@ static ValueLatticeElement getValueFromICmpCondition(Value *Val, ICmpInst *ICI,
}
// If (X urem Modulus) >= C, then X >= C.
// If trunc X >= C, then X >= C.
// TODO: An upper bound could be computed as well.
if (match(LHS, m_URem(m_Specific(Val), m_Value())) &&
if (match(LHS, m_CombineOr(m_URem(m_Specific(Val), m_Value()),
m_Trunc(m_Specific(Val)))) &&
match(RHS, m_APInt(C))) {
// Use the icmp region so we don't have to deal with different predicates.
ConstantRange CR = ConstantRange::makeExactICmpRegion(EdgePred, *C);
if (!CR.isEmptySet())
return ValueLatticeElement::getRange(ConstantRange::getNonEmpty(
CR.getUnsignedMin(), APInt(BitWidth, 0)));
CR.getUnsignedMin().zextOrSelf(BitWidth), APInt(BitWidth, 0)));
}
return ValueLatticeElement::getOverdefined();

View File

@ -1131,14 +1131,12 @@ define void @trunc_icmp_ule(i32 %x, i1* %p) {
; CHECK-NEXT: [[C:%.*]] = icmp uge i8 [[T]], 5
; CHECK-NEXT: br i1 [[C]], label [[TRUE:%.*]], label [[FALSE:%.*]]
; CHECK: true:
; CHECK-NEXT: [[C1:%.*]] = icmp uge i32 [[X]], 5
; CHECK-NEXT: store i1 [[C1]], i1* [[P:%.*]], align 1
; CHECK-NEXT: store i1 true, i1* [[P:%.*]], align 1
; CHECK-NEXT: [[C2:%.*]] = icmp ugt i32 [[X]], 5
; CHECK-NEXT: store i1 [[C2]], i1* [[P]], align 1
; CHECK-NEXT: [[C3:%.*]] = icmp ule i32 [[X]], 5
; CHECK-NEXT: store i1 [[C3]], i1* [[P]], align 1
; CHECK-NEXT: [[C4:%.*]] = icmp ult i32 [[X]], 5
; CHECK-NEXT: store i1 [[C4]], i1* [[P]], align 1
; CHECK-NEXT: store i1 false, i1* [[P]], align 1
; CHECK-NEXT: ret void
; CHECK: false:
; CHECK-NEXT: [[C1_2:%.*]] = icmp uge i32 [[X]], 5
@ -1184,14 +1182,12 @@ define void @trunc_icmp_eq(i32 %x, i1* %p) {
; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[T]], 5
; CHECK-NEXT: br i1 [[C]], label [[TRUE:%.*]], label [[FALSE:%.*]]
; CHECK: true:
; CHECK-NEXT: [[C1:%.*]] = icmp uge i32 [[X]], 5
; CHECK-NEXT: store i1 [[C1]], i1* [[P:%.*]], align 1
; CHECK-NEXT: store i1 true, i1* [[P:%.*]], align 1
; CHECK-NEXT: [[C2:%.*]] = icmp ugt i32 [[X]], 5
; CHECK-NEXT: store i1 [[C2]], i1* [[P]], align 1
; CHECK-NEXT: [[C3:%.*]] = icmp ule i32 [[X]], 5
; CHECK-NEXT: store i1 [[C3]], i1* [[P]], align 1
; CHECK-NEXT: [[C4:%.*]] = icmp ult i32 [[X]], 5
; CHECK-NEXT: store i1 [[C4]], i1* [[P]], align 1
; CHECK-NEXT: store i1 false, i1* [[P]], align 1
; CHECK-NEXT: ret void
; CHECK: false:
; CHECK-NEXT: [[C1_2:%.*]] = icmp uge i32 [[X]], 5