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[InstCombine] improve sub with bool folds 

There's a patchwork of existing transforms trying to handle
these cases, but as seen in the changed test, we weren't
catching them all.

llvm-svn: 333845
This commit is contained in:
Sanjay Patel 2018-06-03 16:35:26 +00:00
parent cc92f5038e
commit 3bd957b7ae
2 changed files with 17 additions and 18 deletions
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27
llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
View File

@ -1571,11 +1571,22 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
return BinaryOperator::CreateSub(Y, X);
if (Constant *C = dyn_cast<Constant>(Op0)) {
bool IsNegate = match(C, m_ZeroInt());
Value *X;
// C - zext(bool) -> bool ? C - 1 : C
if (match(Op1, m_ZExt(m_Value(X))) &&
X->getType()->getScalarSizeInBits() == 1)
if (match(Op1, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)) {
// 0 - (zext bool) --> sext bool
// C - (zext bool) --> bool ? C - 1 : C
if (IsNegate)
return CastInst::CreateSExtOrBitCast(X, I.getType());
return SelectInst::Create(X, SubOne(C), C);
}
if (match(Op1, m_SExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)) {
// 0 - (sext bool) --> zext bool
// C - (sext bool) --> bool ? C + 1 : C
if (IsNegate)
return CastInst::CreateZExtOrBitCast(X, I.getType());
return SelectInst::Create(X, AddOne(C), C);
}
// C - ~X == X + (1+C)
if (match(Op1, m_Not(m_Value(X))))
@ -1595,16 +1606,6 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
Constant *C2;
if (match(Op1, m_Add(m_Value(X), m_Constant(C2))))
return BinaryOperator::CreateSub(ConstantExpr::getSub(C, C2), X);
// Fold (sub 0, (zext bool to B)) --> (sext bool to B)
if (C->isNullValue() && match(Op1, m_ZExt(m_Value(X))))
if (X->getType()->isIntOrIntVectorTy(1))
return CastInst::CreateSExtOrBitCast(X, Op1->getType());
// Fold (sub 0, (sext bool to B)) --> (zext bool to B)
if (C->isNullValue() && match(Op1, m_SExt(m_Value(X))))
if (X->getType()->isIntOrIntVectorTy(1))
return CastInst::CreateZExtOrBitCast(X, Op1->getType());
}
const APInt *Op0C;

8
llvm/test/Transforms/InstCombine/zext-bool-add-sub.ll
View File

@ -214,8 +214,8 @@ define <2 x i64> @sext_negate_vec(<2 x i1> %A) {
define <2 x i64> @sext_negate_vec_undef_elt(<2 x i1> %A) {
; CHECK-LABEL: @sext_negate_vec_undef_elt(
; CHECK-NEXT: [[TMP1:%.*]] = zext <2 x i1> [[A:%.*]] to <2 x i64>
; CHECK-NEXT: ret <2 x i64> [[TMP1]]
; CHECK-NEXT: [[SUB:%.*]] = zext <2 x i1> [[A:%.*]] to <2 x i64>
; CHECK-NEXT: ret <2 x i64> [[SUB]]
;
%ext = sext <2 x i1> %A to <2 x i64>
%sub = sub <2 x i64> <i64 0, i64 undef>, %ext
@ -232,12 +232,10 @@ define i64 @sext_sub_const(i1 %A) {
ret i64 %sub
}
; FIXME: This doesn't correspond to the zext pattern above. We should have a select.
define i64 @sext_sub_const_extra_use(i1 %A) {
; CHECK-LABEL: @sext_sub_const_extra_use(
; CHECK-NEXT: [[EXT:%.*]] = sext i1 [[A:%.*]] to i64
; CHECK-NEXT: [[SUB:%.*]] = sub nsw i64 42, [[EXT]]
; CHECK-NEXT: [[SUB:%.*]] = select i1 [[A]], i64 43, i64 42
; CHECK-NEXT: call void @use(i64 [[EXT]])
; CHECK-NEXT: ret i64 [[SUB]]
;