On 02/04/2015 11:17 PM, Ingo Molnar wrote:
* H. Peter Anvin <hpa@xxxxxxxxx> wrote:On 01/19/2015 02:04 AM, Peter Zijlstra wrote:On Mon, Jan 19, 2015 at 07:54:22AM +1200, Linus Torvalds wrote:Why? The 8- and 16- bit versions are the same as the 32-bit one. This seems pointless. If you want something where the sign is in bit 3, they all return the same value, just the return type differs, but that's really a *caller* thing, no?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?and instead considers 8-bit values to occupy the whole register, but that means only four are available in 32-bit mode.So where are we with this? Should I consider: 7e9358073d3f ("bitops: Add sign_extend8(), 16 and 64 functions") NAK-ed due to having marginal benefits, or due to having no benefits whatsoever? How about the two patch series from Martin Keppling - that does seem to be both beneficial and correct, agreed?
Do you mean the two patches improving the documentation of sign_extend32 and adding sign_extend64 ? I thought those would be valuable. The discussion resulted in sign_extend32() being used for non-32-bit operations, so that by itself was quite useful. Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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