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[PATCH]: Fix __builtin_apply problems with MMX registers

Quoting Richard Henderson <>:

> > For __builtin_apply ()problems, I suggest that called function (for i386)
> > should NOT use MMX registers, and that it is always called in
> FPU_MODE_387.
> I agree.  You planning on working on this I assume?

  In this message, please find a patch that fixes __builtin_apply problems with
MMX registers. The problem was, that regparm MMX registers were blindly passed
to referenced function, and MMX registers were used for return value together
with x87 return registers in function, referenced in __builtin_apply. This is
wrong, as it confuses processor to switch FPU to MMX mode at function entry and
to MMX mode at function exit, clobbering the result in FP registers. (this
switching also confuses mode_exit function of MMX/x87 switching).

  The proposed solution introduces two defines, that overload
FUNCTION_VALUE_REGNO_P and FUNCTION_ARG_REGNO_P defines in builtin_apply.c. With
this change __builtin_apply, __builtin_apply_args and __builtin_return don't
reference MMX registers anymore, while MMX registers can still be used as
function regparms / return registers for other functions.

  This problem is unrelated to MMX/x87 switching patch.

  Patch ware bootstrapped on i686-pc-linux-gnu, regtested for c and c++. With
this patch applied, MMX/x87 switching patch introduces no regressions.

  OK for mainline?

2005-07-14  Uros Bizjak  <>

	to FUNCTION_VALUE_REGNO_P if undefined.
	FUNCTION_ARG_REGNO_P if undefined.
	(apply_args_size): Use FUNCTION_ARG_REGNO_P_APPLY_ARGS.
	(apply_result_size): Use FUNCTION_VALUE_REGNO_P_APPLY_RESULT.

	* config/i386/i386-protos.h (ix86_function_value_regno_p):
	Add new bool argument.
	(ix86_function_arg_regno_p): Add new bool argument.
	* config/i386/i386.h (FUNCTION_VALUE_REGNO_P): Add new
	argument in call to ix86_function_value_regno_p ().
	(FUNCTION_ARG_REGNO_P): Add new argument in call to
	ix86_function_arg_regno_p ().
	* config/i386/i386.c (ix86_function_arg_regno_p): Add new
	from_builtin function argument. Do not return true for MMX
	registers when from_builtin is set.
	(ix86_function_value_regno_p): Add new from_builtin function
	argument. Do not return true for MMX registers when 
	from_builtin is set.


Attachment: apply.diff
Description: Binary data

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