[llvm] [InstCombine] Resolve TODO: Remove one-time check if other logic operand (Y) is constant (PR #77973)

[Nikita Popov via llvm-commits]

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@@ -430,6 +430,21 @@ define i8 @shl_sub(i8 %x, i8 %y) {
   ret i8 %sh1
 }
 
+define i8 @shl_sub_multiuse(i8 %x) {
+; CHECK-LABEL: @shl_sub_multiuse(
+; CHECK-NEXT:    [[SH0:%.*]] = shl i8 [[X:%.*]], 3
+; CHECK-NEXT:    call void @use(i8 [[SH0]])
+; CHECK-NEXT:    [[R:%.*]] = shl i8 [[X]], 5
+; CHECK-NEXT:    [[SH1:%.*]] = add i8 [[R]], 88
+; CHECK-NEXT:    ret i8 [[SH1]]
+;
+  %sh0 = shl i8 %x, 3
+  %r = sub i8 %sh0, 42
+  call void @use(i8 %sh0)
+  %sh1 = shl i8 %r, 2
+  ret i8 %sh1
+}
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nikic wrote:

Please add the variant with a non-constant operand again...

https://github.com/llvm/llvm-project/pull/77973