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[InstCombine] (Y + ~X) + 1 --> Y - X fold (PR42459)
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Summary:
To be noted, this pattern is not unhandled by instcombine per-se,
it is somehow does end up being folded when one runs opt -O3,
but not if it's just -instcombine. Regardless, that fold is
indirect, depends on some other folds, and is thus blind
when there are extra uses.

This does address the regression being exposed in D63992.

https://godbolt.org/z/7DGltU
https://rise4fun.com/Alive/EPO0

Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=42459 | PR42459 ]]

Reviewers: spatel, nikic, huihuiz

Reviewed By: spatel

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63993

llvm-svn: 364792
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@LebedevRI
LebedevRI committed Jul 1, 2019
1 parent 72b8d41 commit 04d3d3b
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Showing 3 changed files with 16 additions and 28 deletions.
5 changes: 4 additions & 1 deletion llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
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Expand Up @@ -1202,7 +1202,10 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {

// (A + 1) + ~B --> A - B
// ~B + (A + 1) --> A - B
if (match(&I, m_c_BinOp(m_Add(m_Value(A), m_One()), m_Not(m_Value(B)))))
// (~B + A) + 1 --> A - B
// (A + ~B) + 1 --> A - B
if (match(&I, m_c_BinOp(m_Add(m_Value(A), m_One()), m_Not(m_Value(B)))) ||
match(&I, m_BinOp(m_c_Add(m_Not(m_Value(B)), m_Value(A)), m_One())))
return BinaryOperator::CreateSub(A, B);

// X % C0 + (( X / C0 ) % C1) * C0 => X % (C0 * C1)
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10 changes: 3 additions & 7 deletions llvm/test/Transforms/InstCombine/add.ll
View file
Expand Up @@ -951,9 +951,7 @@ define i32 @add_not_increment_commuted(i32 %A, i32 %B) {
define i32 @add_to_sub(i32 %M, i32 %B) {
; CHECK-LABEL: @add_to_sub(
; CHECK-NEXT: [[A:%.*]] = mul i32 [[M:%.*]], 42
; CHECK-NEXT: [[C:%.*]] = xor i32 [[B:%.*]], -1
; CHECK-NEXT: [[D:%.*]] = add i32 [[A]], [[C]]
; CHECK-NEXT: [[E:%.*]] = add i32 [[D]], 1
; CHECK-NEXT: [[E:%.*]] = sub i32 [[A]], [[B:%.*]]
; CHECK-NEXT: ret i32 [[E]]
;
%A = mul i32 %M, 42 ; thwart complexity-based ordering
Expand All @@ -966,10 +964,8 @@ define i32 @add_to_sub(i32 %M, i32 %B) {
; E = (~B + A) + 1 = A - B
define i32 @add_to_sub2(i32 %A, i32 %M) {
; CHECK-LABEL: @add_to_sub2(
; CHECK-NEXT: [[B:%.*]] = mul i32 [[M:%.*]], 42
; CHECK-NEXT: [[C:%.*]] = xor i32 [[B]], -1
; CHECK-NEXT: [[D:%.*]] = add i32 [[C]], [[A:%.*]]
; CHECK-NEXT: [[E:%.*]] = add i32 [[D]], 1
; CHECK-NEXT: [[TMP1:%.*]] = mul i32 [[M:%.*]], -42
; CHECK-NEXT: [[E:%.*]] = add i32 [[TMP1]], [[A:%.*]]
; CHECK-NEXT: ret i32 [[E]]
;
%B = mul i32 %M, 42 ; thwart complexity-based ordering
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29 changes: 9 additions & 20 deletions llvm/test/Transforms/InstCombine/fold-inc-of-add-of-not-x-and-y-to-sub-x-from-y.ll
View file
Expand Up @@ -12,9 +12,7 @@

define i32 @t0(i32 %x, i32 %y) {
; CHECK-LABEL: @t0(
; CHECK-NEXT: [[T0:%.*]] = xor i32 [[X:%.*]], -1
; CHECK-NEXT: [[T1:%.*]] = add i32 [[T0]], [[Y:%.*]]
; CHECK-NEXT: [[T2:%.*]] = add i32 [[T1]], 1
; CHECK-NEXT: [[T2:%.*]] = sub i32 [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: ret i32 [[T2]]
;
%t0 = xor i32 %x, -1
Expand All @@ -29,9 +27,7 @@ define i32 @t0(i32 %x, i32 %y) {

define <4 x i32> @t1_vec_splat(<4 x i32> %x, <4 x i32> %y) {
; CHECK-LABEL: @t1_vec_splat(
; CHECK-NEXT: [[T0:%.*]] = xor <4 x i32> [[X:%.*]], <i32 -1, i32 -1, i32 -1, i32 -1>
; CHECK-NEXT: [[T1:%.*]] = add <4 x i32> [[T0]], [[Y:%.*]]
; CHECK-NEXT: [[T2:%.*]] = add <4 x i32> [[T1]], <i32 1, i32 1, i32 1, i32 1>
; CHECK-NEXT: [[T2:%.*]] = sub <4 x i32> [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: ret <4 x i32> [[T2]]
;
%t0 = xor <4 x i32> %x, <i32 -1, i32 -1, i32 -1, i32 -1>
Expand All @@ -42,9 +38,7 @@ define <4 x i32> @t1_vec_splat(<4 x i32> %x, <4 x i32> %y) {

define <4 x i32> @t2_vec_undef0(<4 x i32> %x, <4 x i32> %y) {
; CHECK-LABEL: @t2_vec_undef0(
; CHECK-NEXT: [[T0:%.*]] = xor <4 x i32> [[X:%.*]], <i32 -1, i32 -1, i32 undef, i32 -1>
; CHECK-NEXT: [[T1:%.*]] = add <4 x i32> [[T0]], [[Y:%.*]]
; CHECK-NEXT: [[T2:%.*]] = add <4 x i32> [[T1]], <i32 1, i32 1, i32 1, i32 1>
; CHECK-NEXT: [[T2:%.*]] = sub <4 x i32> [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: ret <4 x i32> [[T2]]
;
%t0 = xor <4 x i32> %x, <i32 -1, i32 -1, i32 undef, i32 -1>
Expand All @@ -55,9 +49,7 @@ define <4 x i32> @t2_vec_undef0(<4 x i32> %x, <4 x i32> %y) {

define <4 x i32> @t3_vec_undef1(<4 x i32> %x, <4 x i32> %y) {
; CHECK-LABEL: @t3_vec_undef1(
; CHECK-NEXT: [[T0:%.*]] = xor <4 x i32> [[X:%.*]], <i32 -1, i32 -1, i32 -1, i32 -1>
; CHECK-NEXT: [[T1:%.*]] = add <4 x i32> [[T0]], [[Y:%.*]]
; CHECK-NEXT: [[T2:%.*]] = add <4 x i32> [[T1]], <i32 1, i32 1, i32 undef, i32 1>
; CHECK-NEXT: [[T2:%.*]] = sub <4 x i32> [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: ret <4 x i32> [[T2]]
;
%t0 = xor <4 x i32> %x, <i32 -1, i32 -1, i32 -1, i32 -1>
Expand All @@ -68,9 +60,7 @@ define <4 x i32> @t3_vec_undef1(<4 x i32> %x, <4 x i32> %y) {

define <4 x i32> @t4_vec_undef2(<4 x i32> %x, <4 x i32> %y) {
; CHECK-LABEL: @t4_vec_undef2(
; CHECK-NEXT: [[T0:%.*]] = xor <4 x i32> [[X:%.*]], <i32 -1, i32 -1, i32 undef, i32 -1>
; CHECK-NEXT: [[T1:%.*]] = add <4 x i32> [[T0]], [[Y:%.*]]
; CHECK-NEXT: [[T2:%.*]] = add <4 x i32> [[T1]], <i32 1, i32 1, i32 undef, i32 1>
; CHECK-NEXT: [[T2:%.*]] = sub <4 x i32> [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: ret <4 x i32> [[T2]]
;
%t0 = xor <4 x i32> %x, <i32 -1, i32 -1, i32 undef, i32 -1>
Expand All @@ -89,8 +79,7 @@ define i32 @t5(i32 %x, i32 %y) {
; CHECK-LABEL: @t5(
; CHECK-NEXT: [[T0:%.*]] = xor i32 [[X:%.*]], -1
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: [[T1:%.*]] = add i32 [[T0]], [[Y:%.*]]
; CHECK-NEXT: [[T2:%.*]] = add i32 [[T1]], 1
; CHECK-NEXT: [[T2:%.*]] = sub i32 [[Y:%.*]], [[X]]
; CHECK-NEXT: ret i32 [[T2]]
;
%t0 = xor i32 %x, -1
Expand All @@ -105,7 +94,7 @@ define i32 @t6(i32 %x, i32 %y) {
; CHECK-NEXT: [[T0:%.*]] = xor i32 [[X:%.*]], -1
; CHECK-NEXT: [[T1:%.*]] = add i32 [[T0]], [[Y:%.*]]
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: [[T2:%.*]] = add i32 [[T1]], 1
; CHECK-NEXT: [[T2:%.*]] = sub i32 [[Y]], [[X]]
; CHECK-NEXT: ret i32 [[T2]]
;
%t0 = xor i32 %x, -1
Expand All @@ -121,7 +110,7 @@ define i32 @t7(i32 %x, i32 %y) {
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: [[T1:%.*]] = add i32 [[T0]], [[Y:%.*]]
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: [[T2:%.*]] = add i32 [[T1]], 1
; CHECK-NEXT: [[T2:%.*]] = sub i32 [[Y]], [[X]]
; CHECK-NEXT: ret i32 [[T2]]
;
%t0 = xor i32 %x, -1
Expand All @@ -145,7 +134,7 @@ define i32 @t8_commutative0(i32 %x) {
; CHECK-NEXT: call void @use32(i32 [[T0]])
; CHECK-NEXT: [[T1:%.*]] = add i32 [[Y]], [[T0]]
; CHECK-NEXT: call void @use32(i32 [[T1]])
; CHECK-NEXT: [[T2:%.*]] = add i32 [[T1]], 1
; CHECK-NEXT: [[T2:%.*]] = sub i32 [[Y]], [[X]]
; CHECK-NEXT: ret i32 [[T2]]
;
%y = call i32 @gen32()
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