[Qemu-devel] target-alpha: An approach to fp insn qualifiers

[Richard Henderson]

One of the other folks here (I'm sorry, I've forgotten who as I 
misplaced the mail) passed me a preliminary patch to tackle the missing 
fp rounding mode support.  That patch added helpers to change the 
rounding mode, and injected them before and after every fp insn that 
forced a rounding mode.

After some thought I decided not to pursue this method for the simple 
reason that TCG does not have native floating point code generation. 
Given that we have to call one helper routine to perform the operation, 
we might as well arrange for that same routine to handle the rounding 
mode manipulation.

Indeed, the patch below doesn't just pass the rounding mode to the 
helper, but all of the qualifier fields.  Thus we can avoid a large 
explosion of helper routines for addt{,/u,/su,sui}{,/c,/m,/d}.

To complete the patch I should add some symbolic defines for /s, /u, etc 
to avoid magic constants cluttering the code.  I should figure out what 
I should pass to helper_excp for each arithmetic exception.  I should 
actually implement the arithmetic exceptions.

That said, these two patches are enough to pass the gcc testsuite with 
no regressions over native hardware.

Comments?


r~

commit-fpu-1
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commit-fpu-2
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