[PATCH] D123043: [X86] Add XOR(X, MIN_SIGNED_VALUE) -> ADD(X, MIN_SIGNED_VALUE) isel patterns (PR52267)

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


================
Comment at: llvm/lib/Target/X86/X86InstrCompiler.td:1529
+
+let AddedComplexity = 5 in {
+def : Pat<(xor_is_add GR8:$src1, imm:$src2),
----------------
craig.topper wrote:
> It occurs to me you could avoid the AddedComplexity by writing
> 
> ```
> def : Pat<(xor GR8:$src1, 128),
>           (ADD8ri GR8:$src1, 128)>;
> def : Pat<(xor GR16:$src1, 32768),
>           (ADD16ri GR16:$src1, 32768)>;
> def : Pat<(xor GR32:$src1, 2147483648),
>           (ADD32ri GR32:$src1, 2147483648)>;
> ```
Those might need to be negative constants.


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https://reviews.llvm.org/D123043