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Re: PATCH: Add OPTION_MASK_ISA_X86_64 and support TARGET_BI_ARCH == 2


Hi H.J.

On 31 Mar 2012, at 20:24, Jack Howarth wrote:

The latest gcc-pr52784-2.patch patch also allows current gcc trunk to
bootstrap on i386-apple-darwin10.

Despite the fact that bootstrap is restored, there remain problems with this patch and some more work is needed.


(a) [trivial] the option 'mx32' is in i386.opt, which means it is exposed to all sub-targets, even if they don't support it.

$ ./gcc/xgcc -Bgcc ../tests/hello.c -mx32 -o hc
/var/folders/OW/OW-PGOtgHbKakssxFpJpkU++-0E/-Tmp-//ccIP9e4Z.s:10:bad register name `%rbp'
/var/folders/OW/OW-PGOtgHbKakssxFpJpkU++-0E/-Tmp-//ccIP9e4Z.s:14:bad register name `%rsi'
etc. etc.


(b) [serious] the m64 ObjC multi-lib is broken on i?86-darwin* (and likely there are other more subtle effects).

This is because the code in config/darwin.c that Joseph pointed out (earlier in this thread) is called for SUBSUBTARGET_OVERRIDE_OPTIONS.

That code sets defaults for, and checks errors for, flags that apply to *-*-darwin* (and are needed for LTO as well as c-family).

In the case of the ObjC ABI (fobjc-abi-version=) we need to default it to "2" @ m64 (and default it to 0 or 1 depending on the darwin version @ m32).

I accept that some of this could possibly be done in driver-self- specs; however, we allow m32/m64 to be unspecified on the c/l and to default for the target. I'm also not yet sure whether %:version- compare() would be applicable to fobjc-abi-version.

Thus, the current trunk implementation is broken by your patch and we need to address that pending other solutions (I'm also very short of free time for Darwin right now - to experiment with the specs solution).

=--=

It is possible that there is an options handling issue, (although I might also have misunderstood) viz:

=========
(current) i386.opt:

;; ISA support

m32
Target RejectNegative Negative(m64) Report InverseMask(ISA_64BIT) Var(ix86_isa_flags) Save
Generate 32bit i386 code


m64
Target RejectNegative Negative(mx32) Report Mask(ABI_64) Var(ix86_isa_flags) Save
Generate 64bit x86-64 code


mx32
Target RejectNegative Negative(m32) Report Mask(ABI_X32) Var(ix86_isa_flags) Save
Generate 32bit x86-64 code


=======
from gccint.pdf (section 8.2):

Negative(othername )
The option will turn oï another option othername, which is the option name
with the leading â-â removed. This chain action will propagate through the
Negative property of the option to be turned oï.
As a consequence, if you have a group of mutually-exclusive options, their
Negative properties should form a circular chain. For example, if options
â-a â, â-b â and â-c â are mutually exclusive, their respective Negative properties
should be âNegative(b )â, âNegative(c )â and âNegative(a )â.


======

I read this as "if the User specifies -a on the command line the inverse of -b *and* the inverse of -c will be applied".

so that when -m64 is issued, the *inverse* of Mask(ABI_X32) should be applied and then the *inverse* of InverseMask(ISA_64BIT) - which would (correctly, for the case we're considering) set MASK_ISA_64BIT.

However, in the example above this does NOT happen - if I set a breakpoint at the entry of x86_internal_override_options - ISA_64BIT ends up as 0 when -m64 is specified on the c/l for i?86-darwin*.

The x86_isa_explicit stuff doesn't appear to get set either, although global_options_set.x_x86_isa... does, which I've used in the attached patch.

so is this an options bug or misunderstanding on my part?

=====

An interim solution to the current scenario (tested by the chaps across the darwin range) is attached.

Is that OK for trunk?

NOTE: I can't apply any patch at present, unless it's considered to be trivial, since my personal FSF (c) assignment is in the process of being transferred to my new employer.

cheers
Iain

Attachment: 186156-x86-darwin-option-fixes.txt
Description: Text document





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