ia32: floating-point-overflow not signaled on EXP

[rme]

From the test suite:

(EXP (+ (LOG MOST-POSITIVE-SINGLE-FLOAT) 100))
(EXP (+ (LOG MOST-POSITIVE-DOUBLE-FLOAT) 100))

Both should signal floating-point-overflow, but instead return "1E++0" and "2E++0"

[gb]

Hmm. It's not clear why we're looking at mxcsr bits after calling #_expf, unless we're really sure that #_expf is using SSE2 and not the x87.

[gb]

Whoops; didn't mean to steal this ...

[rme]

On Darwin, exp() and expf() appear (from looking at disassembler output) not to use the x87 unit. Probably they are the routines from the msun library as found in FreeBSD. I'd expect the mxcsr bits would tell the true story there.

On Linux (at least with our current compiler flags), exp() and expf() are implemented with x87 instructions.

[rme]

r11110 fixes this for Darwin, whose exp() and expf() don't use the x87.

Some other approach will be needed on Linux.

[gb]

If I read the diagrams correctly, the low 6 ("exception occurred") bits in the MXCSR have the same meaning as the low 6 bits in the x87 status register, so we may be able to get away with just storing the x87 status word in the TCR.

[rme]

Should now work on Linux (at least) as of r11294.