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[ConstraintElimination] Support add with precondition. 

If we can prove that an addition without wrap flags won't wrap, decompse
the operation.

Issue #48253
This commit is contained in:
Florian Hahn 2022-02-11 20:26:25 +00:00
parent f9f78a2c40
commit 66400fc2dd
No known key found for this signature in database
GPG Key ID: CF59919C6547A668
2 changed files with 10 additions and 4 deletions
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6
llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
View File

@ -229,6 +229,12 @@ decompose(Value *V, SmallVector<PreconditionTy, 4> &Preconditions,
ConstantInt *CI;
if (match(V, m_NUWAdd(m_Value(Op0), m_ConstantInt(CI))))
return {{CI->getSExtValue(), nullptr}, {1, Op0}};
if (match(V, m_Add(m_Value(Op0), m_ConstantInt(CI))) && CI->isNegative()) {
Preconditions.emplace_back(
CmpInst::ICMP_UGE, Op0,
ConstantInt::get(Op0->getType(), CI->getSExtValue() * -1));
return {{CI->getSExtValue(), nullptr}, {1, Op0}};
}
if (match(V, m_NUWAdd(m_Value(Op0), m_Value(Op1))))
return {{0, nullptr}, {1, Op0}, {1, Op1}};

8
llvm/test/Transforms/ConstraintElimination/wrapping-math.ll
View File

@ -22,7 +22,7 @@ define i1 @wrapping_add_known_1(i8 %a) {
; CHECK: then:
; CHECK-NEXT: [[SUB_1:%.*]] = add i8 [[A]], -1
; CHECK-NEXT: [[C_1:%.*]] = icmp eq i8 [[SUB_1]], 0
; CHECK-NEXT: ret i1 [[C_1]]
; CHECK-NEXT: ret i1 true
; CHECK: else:
; CHECK-NEXT: [[SUB_2:%.*]] = add i8 [[A]], -1
; CHECK-NEXT: [[C_2:%.*]] = icmp eq i8 [[SUB_2]], 0
@ -85,7 +85,7 @@ define i1 @test_48253_eq_ne(i8 %a, i8 %b) {
; CHECK-NEXT: [[T_1:%.*]] = icmp ult i8 [[SUB_1]], [[A]]
; CHECK-NEXT: [[SUB_2:%.*]] = add i8 [[B]], -2
; CHECK-NEXT: [[C_2:%.*]] = icmp ult i8 [[SUB_2]], [[A]]
; CHECK-NEXT: [[XOR_1:%.*]] = xor i1 [[T_1]], [[C_2]]
; CHECK-NEXT: [[XOR_1:%.*]] = xor i1 true, [[C_2]]
; CHECK-NEXT: ret i1 [[XOR_1]]
; CHECK: exit.1:
; CHECK-NEXT: [[SUB_3:%.*]] = add i8 [[B]], -1
@ -133,9 +133,9 @@ define i1 @test_ult(i8 %a, i8 %b) {
; CHECK: if.end:
; CHECK-NEXT: [[T_1:%.*]] = icmp ult i8 [[SUB_1]], [[B]]
; CHECK-NEXT: [[T_2:%.*]] = icmp ult i8 [[SUB_2]], [[B]]
; CHECK-NEXT: [[XOR_1:%.*]] = xor i1 [[T_1]], [[T_2]]
; CHECK-NEXT: [[XOR_1:%.*]] = xor i1 true, true
; CHECK-NEXT: [[T_3:%.*]] = icmp ult i8 [[SUB_3]], [[B]]
; CHECK-NEXT: [[XOR_2:%.*]] = xor i1 [[XOR_1]], [[T_3]]
; CHECK-NEXT: [[XOR_2:%.*]] = xor i1 [[XOR_1]], true
; CHECK-NEXT: [[C_1:%.*]] = icmp ult i8 [[SUB_4]], [[B]]
; CHECK-NEXT: [[XOR_3:%.*]] = xor i1 [[XOR_2]], [[C_1]]
; CHECK-NEXT: [[C_2:%.*]] = icmp ult i8 [[ADD_1]], [[B]]