Messages in this thread | | | Date | Thu, 05 Feb 2015 08:39:19 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [tip:core/types] bitops: Add sign_extend8(), 16 and 64 functions |
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On 02/04/2015 11:17 PM, Ingo Molnar wrote: >>> >>> Even for the 8bit ones? Since we have the *H and *L register >>> we have more 8 bit regs than we have 16/32 bit regs and it >>> might just be worth it. >> >> Fewer, actually. gcc doesn't really use the H registers much, > > Is that true for other compilers as well? >
Probably. It wrecks havoc on register allocation, and it doesn't buy that much, especially on 64 bits where all the registers can be used for 8-bit operations.
-hpa
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