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Re: clang .code16 with -Os producing larger code that it needs to

From: David Woodhouse
Subject: Re: clang .code16 with -Os producing larger code that it needs to
Date: Fri, 20 Feb 2015 16:05:08 +0000

On Fri, 2015-02-20 at 16:46 +0100, Vladimir 'φ-coder/phcoder' Serbinenko
> All labels are local to the source file. If I use %eax instead of %ebx
> in first example I get the short code. For the second example how does
> clang detect that offset fits into one byte for issuing EB XX sequence
> which is issued in resulting file in several places. Can we use the
> same mechanism to detect when issuing 16-bit reference and keep 32-bit
> one for external references?

It's been a while since I looked at this... but I think for the short
jumps we just emit the 8-bit version and there's a fixup which can go
back and re-emit the instruction in 32-bit mode if it finds it doesn't

Do we just need to support a similar fixup for promoting 16-bit to
32-bit relocations?


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