[NFC][InstCombine] Add tests for (~x) a>> y --> ~(x a>> y) fold (PR48995)

See https://bugs.llvm.org/show_bug.cgi?id=48995

diff --git a/llvm/test/Transforms/InstCombine/hoist-not-from-ashr-operand.ll b/llvm/test/Transforms/InstCombine/hoist-not-from-ashr-operand.ll
new file mode 100644 (file)
index 0000000..2504800
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/hoist-not-from-ashr-operand.ll
@@ -0,0 +1,68 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; Transform
+;   (~x) a>> y
+; into:
+;   ~(x a>> y)
+
+declare void @use8(i8)
+
+; Most basic positive test
+define i8 @t0(i8 %x, i8 %y) {
+; CHECK-LABEL: @t0(
+; CHECK-NEXT:    [[NOT_X:%.*]] = xor i8 [[X:%.*]], -1
+; CHECK-NEXT:    [[ASHR:%.*]] = ashr i8 [[NOT_X]], [[Y:%.*]]
+; CHECK-NEXT:    ret i8 [[ASHR]]
+;
+  %not_x = xor i8 %x, -1
+  %ashr = ashr i8 %not_x, %y
+  ret i8 %ashr
+}
+; 'exact'-ness isn't preserved!
+define i8 @t1(i8 %x, i8 %y) {
+; CHECK-LABEL: @t1(
+; CHECK-NEXT:    [[NOT_X:%.*]] = xor i8 [[X:%.*]], -1
+; CHECK-NEXT:    [[ASHR:%.*]] = ashr exact i8 [[NOT_X]], [[Y:%.*]]
+; CHECK-NEXT:    ret i8 [[ASHR]]
+;
+  %not_x = xor i8 %x, -1
+  %ashr = ashr exact i8 %not_x, %y
+  ret i8 %ashr
+}
+; Basic vector test
+define <2 x i8> @t2_vec(<2 x i8> %x, <2 x i8> %y) {
+; CHECK-LABEL: @t2_vec(
+; CHECK-NEXT:    [[NOT_X:%.*]] = xor <2 x i8> [[X:%.*]], <i8 -1, i8 -1>
+; CHECK-NEXT:    [[ASHR:%.*]] = ashr <2 x i8> [[NOT_X]], [[Y:%.*]]
+; CHECK-NEXT:    ret <2 x i8> [[ASHR]]
+;
+  %not_x = xor <2 x i8> %x, <i8 -1, i8 -1>
+  %ashr = ashr <2 x i8> %not_x, %y
+  ret <2 x i8> %ashr
+}
+; Note that we must sanitize undef elts of -1 constant to -1 or 0.
+define <2 x i8> @t3_vec_undef(<2 x i8> %x, <2 x i8> %y) {
+; CHECK-LABEL: @t3_vec_undef(
+; CHECK-NEXT:    [[NOT_X:%.*]] = xor <2 x i8> [[X:%.*]], <i8 -1, i8 undef>
+; CHECK-NEXT:    [[ASHR:%.*]] = ashr <2 x i8> [[NOT_X]], [[Y:%.*]]
+; CHECK-NEXT:    ret <2 x i8> [[ASHR]]
+;
+  %not_x = xor <2 x i8> %x, <i8 -1, i8 undef>
+  %ashr = ashr <2 x i8> %not_x, %y
+  ret <2 x i8> %ashr
+}
+
+; Extra use prevents the fold.
+define i8 @n4(i8 %x, i8 %y) {
+; CHECK-LABEL: @n4(
+; CHECK-NEXT:    [[NOT_X:%.*]] = xor i8 [[X:%.*]], -1
+; CHECK-NEXT:    call void @use8(i8 [[NOT_X]])
+; CHECK-NEXT:    [[ASHR:%.*]] = ashr i8 [[NOT_X]], [[Y:%.*]]
+; CHECK-NEXT:    ret i8 [[ASHR]]
+;
+  %not_x = xor i8 %x, -1
+  call void @use8(i8 %not_x)
+  %ashr = ashr i8 %not_x, %y
+  ret i8 %ashr
+}