[NFC][InstCombine] Tests for ((~x) + y) + 1 -> y - x fold fold (PR42459)

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.

https://bugs.llvm.org/show_bug.cgi?id=42459
https://rise4fun.com/Alive/EPO0

llvm-svn: 364749

1 files changed, 184 insertions, 0 deletions

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
new file mode 100644
index 00000000000..54e3b87df8b
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/fold-inc-of-add-of-not-x-and-y-to-sub-x-from-y.ll
@@ -0,0 +1,184 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -instcombine -S < %s | FileCheck %s
+
+; Given:
+;   add (add (xor %x, -1), %y), 1
+; Transform it to:
+;   sub %y, %x
+
+;------------------------------------------------------------------------------;
+; Scalar tests
+;------------------------------------------------------------------------------;
+
+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:    ret i32 [[T2]]
+;
+  %t0 = xor i32 %x, -1
+  %t1 = add i32 %t0, %y
+  %t2 = add i32 %t1, 1
+  ret i32 %t2
+}
+
+;------------------------------------------------------------------------------;
+; Vector tests
+;------------------------------------------------------------------------------;
+
+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:    ret <4 x i32> [[T2]]
+;
+  %t0 = xor <4 x i32> %x, <i32 -1, i32 -1, i32 -1, i32 -1>
+  %t1 = add <4 x i32> %t0, %y
+  %t2 = add <4 x i32> %t1, <i32 1, i32 1, i32 1, i32 1>
+  ret <4 x i32> %t2
+}
+
+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:    ret <4 x i32> [[T2]]
+;
+  %t0 = xor <4 x i32> %x, <i32 -1, i32 -1, i32 undef, i32 -1>
+  %t1 = add <4 x i32> %t0, %y
+  %t2 = add <4 x i32> %t1, <i32 1, i32 1, i32 1, i32 1>
+  ret <4 x i32> %t2
+}
+
+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:    ret <4 x i32> [[T2]]
+;
+  %t0 = xor <4 x i32> %x, <i32 -1, i32 -1, i32 -1, i32 -1>
+  %t1 = add <4 x i32> %t0, %y
+  %t2 = add <4 x i32> %t1, <i32 1, i32 1, i32 undef, i32 1>
+  ret <4 x i32> %t2
+}
+
+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:    ret <4 x i32> [[T2]]
+;
+  %t0 = xor <4 x i32> %x, <i32 -1, i32 -1, i32 undef, i32 -1>
+  %t1 = add <4 x i32> %t0, %y
+  %t2 = add <4 x i32> %t1, <i32 1, i32 1, i32 undef, i32 1>
+  ret <4 x i32> %t2
+}
+
+;------------------------------------------------------------------------------;
+; One-use tests
+;------------------------------------------------------------------------------;
+
+declare void @use32(i32)
+
+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:    ret i32 [[T2]]
+;
+  %t0 = xor i32 %x, -1
+  call void @use32(i32 %t0)
+  %t1 = add i32 %t0, %y
+  %t2 = add i32 %t1, 1
+  ret i32 %t2
+}
+
+define i32 @t6(i32 %x, i32 %y) {
+; CHECK-LABEL: @t6(
+; 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:    ret i32 [[T2]]
+;
+  %t0 = xor i32 %x, -1
+  %t1 = add i32 %t0, %y
+  call void @use32(i32 %t1)
+  %t2 = add i32 %t1, 1
+  ret i32 %t2
+}
+
+define i32 @t7(i32 %x, i32 %y) {
+; CHECK-LABEL: @t7(
+; CHECK-NEXT:    [[T0:%.*]] = xor i32 [[X:%.*]], -1
+; 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:    ret i32 [[T2]]
+;
+  %t0 = xor i32 %x, -1
+  call void @use32(i32 %t0)
+  %t1 = add i32 %t0, %y
+  call void @use32(i32 %t1)
+  %t2 = add i32 %t1, 1
+  ret i32 %t2
+}
+
+;------------------------------------------------------------------------------;
+; Commutativity
+;------------------------------------------------------------------------------;
+
+declare i32 @gen32()
+
+define i32 @t8_commutative(i32 %x) {
+; CHECK-LABEL: @t8_commutative(
+; CHECK-NEXT:    [[Y:%.*]] = call i32 @gen32()
+; CHECK-NEXT:    [[T0:%.*]] = xor i32 [[X:%.*]], -1
+; CHECK-NEXT:    [[T1:%.*]] = add i32 [[Y]], [[T0]]
+; CHECK-NEXT:    [[T2:%.*]] = add i32 [[T1]], 1
+; CHECK-NEXT:    ret i32 [[T2]]
+;
+  %y = call i32 @gen32()
+  %t0 = xor i32 %x, -1
+  %t1 = add i32 %y, %t0 ; swapped
+  %t2 = add i32 %t1, 1
+  ret i32 %t2
+}
+
+;------------------------------------------------------------------------------;
+; Basic negative tests
+;------------------------------------------------------------------------------;
+
+define i32 @n9(i32 %x, i32 %y) {
+; CHECK-LABEL: @n9(
+; CHECK-NEXT:    [[T0:%.*]] = xor i32 [[X:%.*]], 2147483647
+; CHECK-NEXT:    [[T1:%.*]] = add i32 [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    [[T2:%.*]] = add i32 [[T1]], 1
+; CHECK-NEXT:    ret i32 [[T2]]
+;
+  %t0 = xor i32 %x, 2147483647 ; not -1
+  %t1 = add i32 %t0, %y
+  %t2 = add i32 %t1, 1
+  ret i32 %t2
+}
+
+define i32 @n10(i32 %x, i32 %y) {
+; CHECK-LABEL: @n10(
+; CHECK-NEXT:    [[T0:%.*]] = xor i32 [[X:%.*]], -1
+; CHECK-NEXT:    [[T1:%.*]] = add i32 [[T0]], [[Y:%.*]]
+; CHECK-NEXT:    [[T2:%.*]] = add i32 [[T1]], 2
+; CHECK-NEXT:    ret i32 [[T2]]
+;
+  %t0 = xor i32 %x, -1
+  %t1 = add i32 %t0, %y
+  %t2 = add i32 %t1, 2 ; not +1
+  ret i32 %t2
+}