[Bug target/98140] Reused register by xsmincdp leads to wrong NaN propagation on Power9
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98140 --- Comment #3 from Jiu Fu Guo --- (In reply to Jiu Fu Guo from comment #2) > (In reply to Alexander Grund from comment #1) > > It looks like this was fixed in 10.1 by this commit > > https://github.com/gcc-mirror/gcc/commit/ > > 37e0df8a9be5a8232f4ccb73cdadb02121ba523f > ... > > `HONOR_NANS (compare_mode)` case. However it still ignores signed zeros. > > 'xsmincdp' may be fine for zeros, it seems '!HONOR_SIGNED_ZEROS' is not > needed. > > > Maybe xsmindp would be a better fit as it preserves the signed zeros. Only > > downside I see is that it converts sNan to qNan which may be an issue. Oh, sorry. for -0 and +0, xsmincdp returns the 2nd operand, xsmindp returns -0.
[Bug target/98140] Reused register by xsmincdp leads to wrong NaN propagation on Power9
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98140 Jiu Fu Guo changed: What|Removed |Added CC||guojiufu at gcc dot gnu.org --- Comment #2 from Jiu Fu Guo --- (In reply to Alexander Grund from comment #1) > It looks like this was fixed in 10.1 by this commit > https://github.com/gcc-mirror/gcc/commit/ > 37e0df8a9be5a8232f4ccb73cdadb02121ba523f ... > `HONOR_NANS (compare_mode)` case. However it still ignores signed zeros. 'xsmincdp' may be fine for zeros, it seems '!HONOR_SIGNED_ZEROS' is not needed. > Maybe xsmindp would be a better fit as it preserves the signed zeros. Only > downside I see is that it converts sNan to qNan which may be an issue.
[Bug target/98140] Reused register by xsmincdp leads to wrong NaN propagation on Power9
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98140 --- Comment #1 from Alexander Grund --- It looks like this was fixed in 10.1 by this commit https://github.com/gcc-mirror/gcc/commit/37e0df8a9be5a8232f4ccb73cdadb02121ba523f However the codegen looks worse: 390: 20 00 9e c3 lfs f28,32(r30) 394: 00 e0 9e ff fcmpu cr7,f30,f28 398: 10 00 9c 41 blt cr7,3a8 39c: 40 00 9e c3 lfs f28,64(r30) 3a0: 58 e0 1e f0 xscmpgtdp vs0,vs30,vs28 3a4: 30 e0 9e f3 xxsel vs28,vs30,vs28,vs0 When switching an (a > b) ? b : a to an xsmincdp, the arguments must be swapped to honor the NaN rules. This would allow this to be used for the `HONOR_NANS (compare_mode)` case. However it still ignores signed zeros. Maybe xsmindp would be a better fit as it preserves the signed zeros. Only downside I see is that it converts sNan to qNan which may be an issue.
