[InstCombine] (Y + ~X) + 1 --> Y - X fold (PR42459)

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

2 files changed, 12 insertions, 27 deletions

diff --git a/llvm/test/Transforms/InstCombine/add.ll b/llvm/test/Transforms/InstCombine/add.ll
index a2f35cc4359..c31c74020fa 100644
--- a/llvm/test/Transforms/InstCombine/add.ll
+++ b/llvm/test/Transforms/InstCombine/add.ll
@@ -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
@@ -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
diff --git a/llvm/test/Transforms/InstCombine/fold-inc-of-add-of-not-x-and-y-to-sub-x-from-y.ll b/llvm/test/Transforms/InstCombine/fold-inc-of-add-of-not-x-and-y-to-sub-x-from-y.ll
index b47863650c3..ae24b923b5d 100644
--- a/llvm/test/Transforms/InstCombine/fold-inc-of-add-of-not-x-and-y-to-sub-x-from-y.ll
+++ b/llvm/test/Transforms/InstCombine/fold-inc-of-add-of-not-x-and-y-to-sub-x-from-y.ll
@@ -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
@@ -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>
@@ -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>
@@ -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>
@@ -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>
@@ -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
@@ -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
@@ -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
@@ -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()