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From: | Alex Bennée |
Subject: | Re: [PATCH v3 41/48] tcg/optimize: Sink commutative operand swapping into fold functions |
Date: | Wed, 27 Oct 2021 14:22:24 +0100 |
User-agent: | mu4e 1.7.4; emacs 28.0.60 |
Richard Henderson <richard.henderson@linaro.org> writes: > On 10/26/21 9:27 AM, Alex Bennée wrote: >> I find this a bit magical. I couldn't find anything about TCGArg except >> it's type: >> typedef tcg_target_ulong TCGArg; > > For an argument that contains a temp, > > static inline TCGArg temp_arg(TCGTemp *ts) > { > return (uintptr_t)ts; > } > > static inline TCGTemp *arg_temp(TCGArg a) > { > return (TCGTemp *)(uintptr_t)a; > } > > i.e. the TCGArg is in fact a pointer. > >> so I'm not sure what to make of -1 in this case. I guess it just means >> we never have a (sum == 0 && dest == a2) leg but it's not obvious >> reading the fold code. > > Indeed. The use of -1 goes back quite a ways. How about > > #define NO_DEST temp_arg(NULL) > > which will also fail to match in that expression? Sounds good to me. It would be nice to document the details of what TCGArg can be in another patch. -- Alex Bennée
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