Messages in this thread | | | From | Eugeniy Paltsev <> | Subject | Re: [PATCH 4/9] ARC: mm: do_page_fault refactor #3: tidyup vma access permission code | Date | Fri, 17 May 2019 22:23:40 +0000 |
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Hmmm,
so load the bool variable from memory is converted to such asm code:
----------------->8------------------- ldb r2,[some_bool_address] extb_s r2,r2 ----------------->8-------------------
Could you please describe that the magic is going on there?
This extb_s instruction looks completely useless here, according on the LDB description from PRM: ----------------->8------------------- LD LDH LDW LDB LDD: The size of the requested data is specified by the data size field <.zz> and by default, data is zero extended from the most-significant bit of the data to the most-significant bit of the destination register. ----------------->8-------------------
Am I missing something?
On Thu, 2019-05-16 at 17:37 +0000, Vineet Gupta wrote: > On 5/16/19 10:24 AM, Eugeniy Paltsev wrote: > > > + unsigned int write = 0, exec = 0, mask; > > > > Probably it's better to use 'bool' type for 'write' and 'exec' as we really use them as a boolean variables. > > Right those are semantics, but the generated code for "bool" is not ideal - given > it is inherently a "char" it is promoted first to an int with an additional EXTB > which I really dislike. > Guess it is more of a style thing. > > -Vineet -- Eugeniy Paltsev | |