Messages in this thread | | | Date | Wed, 10 Nov 2021 06:14:28 -0600 | From | Segher Boessenkool <> | Subject | Re: [PATCH 20/22] x86,word-at-a-time: Remove .fixup usage |
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Hi!
On Tue, Nov 09, 2021 at 10:07:36PM +0100, Peter Zijlstra wrote: > On Tue, Nov 09, 2021 at 11:22:44AM -0800, Nick Desaulniers wrote: > > I think the use of this feature (label-attributes) here isn't > > necessary though; because of the use of outputs, the "fallthrough" > > basic block needs to be placed immediately after the basic block > > terminated by the asm goto, at least in LLVM. Was different ordering > > of basic blocks observed with GCC without this label attribute? > > GCC does the same, but I wanted to have the exception stuff be in > .text.cold, but alas it doesn't do that. I left the attribute because of > it's descriptive value. > > > Unless the cold attribute is helping move > > ("shrink-wrap"?)
Shrink-wrapping is something else entirely.
>> the basic block to a whole other section > > (.text.cold.)? > > I was hoping it would do that, but it doesn't on gcc-11.
A cold basic block can never dominate a non-cold basic block. GCC will fix things up when it notices this property is violated, so marking random blocks as "cold" will not be very effective.
Segher
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