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[InstCombine] simplify average of lsb #95684

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Merged
merged 7 commits into from
Jun 17, 2024
Merged

[InstCombine] simplify average of lsb #95684

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3734ce9
simplify average of lsb
c8ef Jun 16, 2024
3530da3
Fold ((X % 2) + (Y % 2)) / 2 --> (X & Y & 1) iff (X u<= 1) && (Y u<= 1)
c8ef Jun 16, 2024
c076cc6
fix comment
c8ef Jun 16, 2024
0979c62
remove unused include
c8ef Jun 16, 2024
6369dec
regen test
c8ef Jun 16, 2024
84f1948
x & y
c8ef Jun 16, 2024
1531c6b
style change
c8ef Jun 17, 2024
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6 changes: 6 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1284,6 +1284,12 @@ Instruction *InstCombinerImpl::visitLShr(BinaryOperator &I) {
return NewSub;
}

// Fold (X + Y) / 2 --> (X & Y) iff (X u<= 1) && (Y u<= 1)
if (match(Op0, m_Add(m_Value(X), m_Value(Y))) && match(Op1, m_One()) &&
computeKnownBits(X, /*Depth=*/0, &I).countMaxActiveBits() <= 1 &&
computeKnownBits(Y, /*Depth=*/0, &I).countMaxActiveBits() <= 1)
return BinaryOperator::CreateAnd(X, Y);

// (sub nuw X, (Y << nuw Z)) >>u exact Z --> (X >>u exact Z) sub nuw Y
if (I.isExact() &&
match(Op0, m_OneUse(m_NUWSub(m_Value(X),
Expand Down
46 changes: 46 additions & 0 deletions llvm/test/Transforms/InstCombine/avg-lsb.ll
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@@ -0,0 +1,46 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
; RUN: opt < %s -passes=instcombine -S | FileCheck %s

define i8 @avg_lsb(i8 %a, i8 %b) {
; CHECK-LABEL: define i8 @avg_lsb(
; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
; CHECK-NEXT: [[REM:%.*]] = and i8 [[A]], 1
; CHECK-NEXT: [[DIV2:%.*]] = and i8 [[REM]], [[B]]
; CHECK-NEXT: ret i8 [[DIV2]]
;
%rem = and i8 %a, 1
%rem1 = and i8 %b, 1
%add = add nuw nsw i8 %rem1, %rem
%div2 = lshr i8 %add, 1
ret i8 %div2
}

define i8 @avg_lsb_mismatch(i8 %a, i8 %b) {
; CHECK-LABEL: define i8 @avg_lsb_mismatch(
; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
; CHECK-NEXT: [[REM:%.*]] = and i8 [[A]], 1
; CHECK-NEXT: [[REM1:%.*]] = and i8 [[B]], 3
; CHECK-NEXT: [[ADD:%.*]] = add nuw nsw i8 [[REM1]], [[REM]]
; CHECK-NEXT: [[DIV2:%.*]] = lshr i8 [[ADD]], 1
; CHECK-NEXT: ret i8 [[DIV2]]
;
%rem = and i8 %a, 1
%rem1 = and i8 %b, 3
%add = add nuw nsw i8 %rem1, %rem
%div2 = lshr i8 %add, 1
ret i8 %div2
}

define <2 x i8> @avg_lsb_vector(<2 x i8> %a, <2 x i8> %b) {
; CHECK-LABEL: define <2 x i8> @avg_lsb_vector(
; CHECK-SAME: <2 x i8> [[A:%.*]], <2 x i8> [[B:%.*]]) {
; CHECK-NEXT: [[REM:%.*]] = and <2 x i8> [[A]], <i8 1, i8 1>
; CHECK-NEXT: [[DIV2:%.*]] = and <2 x i8> [[REM]], [[B]]
; CHECK-NEXT: ret <2 x i8> [[DIV2]]
;
%rem = and <2 x i8> %a, <i8 1, i8 1>
%rem1 = and <2 x i8> %b, <i8 1, i8 1>
%add = add nuw nsw <2 x i8> %rem1, %rem
%div2 = lshr <2 x i8> %add, <i8 1, i8 1>
ret <2 x i8> %div2
}
16 changes: 7 additions & 9 deletions llvm/test/Transforms/InstCombine/lshr.ll
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Expand Up @@ -1390,8 +1390,8 @@ define i8 @not_signbit_trunc(i16 %x) {

define i2 @bool_add_lshr(i1 %a, i1 %b) {
; CHECK-LABEL: @bool_add_lshr(
; CHECK-NEXT: [[TMP1:%.*]] = and i1 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = zext i1 [[TMP1]] to i2
; CHECK-NEXT: [[LSHR1:%.*]] = and i1 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = zext i1 [[LSHR1]] to i2
; CHECK-NEXT: ret i2 [[LSHR]]
;
%zext.a = zext i1 %a to i2
Expand Down Expand Up @@ -1436,8 +1436,8 @@ define i2 @bool_add_ashr(i1 %a, i1 %b) {

define <2 x i8> @bool_add_lshr_vec(<2 x i1> %a, <2 x i1> %b) {
; CHECK-LABEL: @bool_add_lshr_vec(
; CHECK-NEXT: [[TMP1:%.*]] = and <2 x i1> [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = zext <2 x i1> [[TMP1]] to <2 x i8>
; CHECK-NEXT: [[LSHR1:%.*]] = and <2 x i1> [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = zext <2 x i1> [[LSHR1]] to <2 x i8>
; CHECK-NEXT: ret <2 x i8> [[LSHR]]
;
%zext.a = zext <2 x i1> %a to <2 x i8>
Expand All @@ -1453,8 +1453,7 @@ define i32 @bool_add_lshr_uses(i1 %a, i1 %b) {
; CHECK-NEXT: call void @use(i32 [[ZEXT_A]])
; CHECK-NEXT: [[ZEXT_B:%.*]] = zext i1 [[B:%.*]] to i32
; CHECK-NEXT: call void @use(i32 [[ZEXT_B]])
; CHECK-NEXT: [[TMP1:%.*]] = and i1 [[A]], [[B]]
; CHECK-NEXT: [[LSHR:%.*]] = zext i1 [[TMP1]] to i32
; CHECK-NEXT: [[LSHR:%.*]] = and i32 [[ZEXT_A]], [[ZEXT_B]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%zext.a = zext i1 %a to i32
Expand All @@ -1473,8 +1472,7 @@ define i32 @bool_add_lshr_uses2(i1 %a, i1 %b) {
; CHECK-NEXT: call void @use(i32 [[ZEXT_B]])
; CHECK-NEXT: [[ADD:%.*]] = add nuw nsw i32 [[ZEXT_A]], [[ZEXT_B]]
; CHECK-NEXT: call void @use(i32 [[ADD]])
; CHECK-NEXT: [[TMP1:%.*]] = and i1 [[A]], [[B]]
; CHECK-NEXT: [[LSHR:%.*]] = zext i1 [[TMP1]] to i32
; CHECK-NEXT: [[LSHR:%.*]] = and i32 [[ZEXT_A]], [[ZEXT_B]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%zext.a = zext i1 %a to i32
Expand All @@ -1496,7 +1494,7 @@ define i32 @bool_add_lshr_uses3(i1 %a, i1 %b) {
; CHECK-NEXT: call void @use(i32 [[ZEXT_B]])
; CHECK-NEXT: [[ADD:%.*]] = add nuw nsw i32 [[ZEXT_A]], [[ZEXT_B]]
; CHECK-NEXT: call void @use(i32 [[ADD]])
; CHECK-NEXT: [[LSHR:%.*]] = lshr i32 [[ADD]], 1
; CHECK-NEXT: [[LSHR:%.*]] = and i32 [[ZEXT_A]], [[ZEXT_B]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%zext.a = zext i1 %a to i32
Expand Down
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