On Tue, 28 Jan 2014, Uros Bizjak wrote: > On Mon, Jan 27, 2014 at 8:44 PM, H.J. Lu <hongjiu...@intel.com> wrote: > > > The .code16gcc directive was added to binutils back in 1999: > > > > --- > > '.code16gcc' provides experimental support for generating 16-bit code > > from gcc, and differs from '.code16' in that 'call', 'ret', 'enter', > > 'leave', 'push', 'pop', 'pusha', 'popa', 'pushf', and 'popf' > > instructions default to 32-bit size. This is so that the stack pointer > > is manipulated in the same way over function calls, allowing access to > > function parameters at the same stack offsets as in 32-bit mode. > > '.code16gcc' also automatically adds address size prefixes where > > necessary to use the 32-bit addressing modes that gcc generates. > > --- > > > > It encodes 32-bit assembly instructions generated by GCC in 16-bit format > > so that GCC can be used to generate 16-bit instructions. To do that, the > > .code16gcc directive may be placed at the very beginning of the assembly > > code. This patch adds -m16 to x86 backend by: > > > > 1. Add -m16 and make it mutually exclusive with -m32, -m64 and -mx32. > > 2. Treat -m16 like -m32 so that --32 is passed to assembler. > > 3. Output .code16gcc at the very beginning of the assembly code. > > 4. Turn off 64-bit ISA when -m16 is used. > > > > Tested on Linux/x86 and Linux/x86-64. OK for trunk? > > > > Thanks. > > > > H.J. > > --- > > PR target/59672 > > * config/i386/gnu-user64.h (SPEC_32): Add "m16|" to "m32". > > (SPEC_X32): Likewise. > > (SPEC_64): Likewise. > > * config/i386/i386.c (ix86_option_override_internal): Turn off > > OPTION_MASK_ISA_64BIT, OPTION_MASK_ABI_X32 and OPTION_MASK_ABI_64 > > for TARGET_16BIT. > > (x86_file_start): Output .code16gcc for TARGET_16BIT. > > * config/i386/i386.h (TARGET_16BIT): New macro. > > (TARGET_16BIT_P): Likewise. > > * config/i386/i386.opt: Add m16. > > * doc/invoke.texi: Document -m16. > > OK for mainline, needs OK from RMs for a backport.
I don't think this is suitable for the branch. Unless there is tremendous need for it somewhere ...? I like the suggested addition of a --code16gcc assembler flag. Please make sure to document the minimum required binutils to make this work. Richard.
