[PATCH]: Expand isinf() as x87 asm

[Uros Bizjak]

Hello!

This patch expands isinf() into inline x87 asm.

Following testcase:
--cut here--
int test(double a)
{
        return isinf(a + 2.0);
}
--cut here--

compiles to (gcc -O2 -fomit-frame-pointer):
test:
        flds    .LC0
        faddl   4(%esp)
        fxam
        fnstsw  %ax
        fstp    %st(0)
        andb    $69, %ah
        cmpb    $5, %ah
        sete    %al
        movzbl  %al, %eax
        ret

Patch was regression tested on i686-pc-linux-gnu for all default languages.

OK for SVN? (Patch needs middle-end approval.)

2007-01-31  Uros Bizjak  <ubizjak@gmail.com>

	* optabs.h (enum optab_index): Add new OTI_isinf.
	(isinf_optab): Define corresponding macro.
	* optabs.c (init_optabs): Initialize isinf_optab.
	* genopinit.c (optabs): Implement isinf_optab using isinf?f2
	patterns.
	* builtins.c (mathfn_built_in): Handle BUILT_IN_ISINF{,F,L}.
	(expand_builtin_interclass_mathfn): Expand BUILT_IN_ISINF{,F,L}
	using isinf_optab.
	(expand_builtin): Expand BUILT_IN_ISINF{,F,L} using
	expand_builtin_interclass_mathfn.
	* reg_stack.c (subst_stack_regs_pat): Handle UNSPEC_FXAM.
	* config/i386/i386.md (UNSPEC_FXAM): New constant.
	(fxam<mode>2_i387): New insn pattern.
	(isinf<mode>2) New expander to implement isinf, isinff and isinfl
	built-in functions as x87 inline asm.

testsuite/ChangeLog:

2007-01-31  Uros Bizjak  <ubizjak@gmail.com>

	* gcc.dg/builtins-64.c: New test.


BTW: I'm almost sure that Richard G. or Jan hardly wait to implement
this expansion also for SSE ;)

Uros.
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