return BinaryOperator::CreateAShr(A, NewShAmt);
}
+ // Splatting a bit of constant-index across a value:
+ // sext (ashr (trunc iN X to iM), M-1) to iN --> ashr (shl X, N-M), N-1
+ // TODO: If the dest type is different, use a cast (adjust use check).
+ if (match(Src, m_OneUse(m_AShr(m_Trunc(m_Value(X)),
+ m_SpecificInt(SrcBitSize - 1)))) &&
+ X->getType() == DestTy) {
+ Constant *ShlAmtC = ConstantInt::get(DestTy, DestBitSize - SrcBitSize);
+ Constant *AshrAmtC = ConstantInt::get(DestTy, DestBitSize - 1);
+ Value *Shl = Builder.CreateShl(X, ShlAmtC);
+ return BinaryOperator::CreateAShr(Shl, AshrAmtC);
+ }
+
if (match(Src, m_VScale(DL))) {
if (CI.getFunction()->hasFnAttribute(Attribute::VScaleRange)) {
unsigned MaxVScale = CI.getFunction()
define i32 @smear_set_bit(i32 %x) {
; CHECK-LABEL: @smear_set_bit(
-; CHECK-NEXT: [[T:%.*]] = trunc i32 [[X:%.*]] to i8
-; CHECK-NEXT: [[A:%.*]] = ashr i8 [[T]], 7
-; CHECK-NEXT: [[S:%.*]] = sext i8 [[A]] to i32
+; CHECK-NEXT: [[TMP1:%.*]] = shl i32 [[X:%.*]], 24
+; CHECK-NEXT: [[S:%.*]] = ashr i32 [[TMP1]], 31
; CHECK-NEXT: ret i32 [[S]]
;
%t = trunc i32 %x to i8
ret i32 %s
}
+; extra use of trunc is ok because we still shorten the use chain
+
define <2 x i32> @smear_set_bit_vec_use1(<2 x i32> %x) {
; CHECK-LABEL: @smear_set_bit_vec_use1(
; CHECK-NEXT: [[T:%.*]] = trunc <2 x i32> [[X:%.*]] to <2 x i5>
; CHECK-NEXT: call void @use_vec(<2 x i5> [[T]])
-; CHECK-NEXT: [[A:%.*]] = ashr <2 x i5> [[T]], <i5 4, i5 4>
-; CHECK-NEXT: [[S:%.*]] = sext <2 x i5> [[A]] to <2 x i32>
+; CHECK-NEXT: [[TMP1:%.*]] = shl <2 x i32> [[X]], <i32 27, i32 27>
+; CHECK-NEXT: [[S:%.*]] = ashr <2 x i32> [[TMP1]], <i32 31, i32 31>
; CHECK-NEXT: ret <2 x i32> [[S]]
;
%t = trunc <2 x i32> %x to <2 x i5>
ret <2 x i32> %s
}
+; negative test - extra use
+
define i32 @smear_set_bit_use2(i32 %x) {
; CHECK-LABEL: @smear_set_bit_use2(
; CHECK-NEXT: [[T:%.*]] = trunc i32 [[X:%.*]] to i8
ret i32 %s
}
+; negative test - must shift all the way across
+
define i32 @smear_set_bit_wrong_shift_amount(i32 %x) {
; CHECK-LABEL: @smear_set_bit_wrong_shift_amount(
; CHECK-NEXT: [[T:%.*]] = trunc i32 [[X:%.*]] to i8
ret i32 %s
}
+; TODO: this could be mask+compare+sext or shifts+trunc
+
define i16 @smear_set_bit_different_dest_type(i32 %x) {
; CHECK-LABEL: @smear_set_bit_different_dest_type(
; CHECK-NEXT: [[T:%.*]] = trunc i32 [[X:%.*]] to i8