[PATCH v3 13/19] RISC-V: Add the RV32 libm-test-ulps

[Joseph Myers]

On Tue, 14 Jul 2020, Maciej W. Rozycki via Libc-alpha wrote:

>  Well, yes.  I just ran `make regen-ulps' consecutively with different 
> `test-wrapper*' variables each time so as to redirect execution either to 
> my HiFive Unleashed board or (user-mode) QEMU.  I have double-checked the 
> logs now and no rebuild was made for subsequent runs, so the very same 
> executables and DSOs were used.

So picking one function and setting its ulps back to the lower value, then 
rerunning the test on whichever of hardware and QEMU gave the higher 
value, should result in a test log showing a specific input to a specific 
function (in a specific rounding mode) for which the results on hardware 
and QEMU differ.  After confirming the difference with a minimal test just 
making that one function call, it should be possible to trace the 
execution of the function, whether in a debugger or inserting printf 
calls, to find the exact instruction for which hardware and QEMU produce 
different results with the same inputs.

-- 
Joseph S. Myers
joseph@codesourcery.com