From: Joseph Myers <jos...@codesourcery.com> The math-emu macros _FP_TO_INT and _FP_TO_INT_ROUND are supposed to saturate their results for out-of-range arguments, except in the case rsigned == 2 (when instead the low bits of the result are taken). However, in the case rsigned == 0 (converting to unsigned integers), they mistakenly produce 0 for positive results and the maximum unsigned integer for negative results, the opposite of correct unsigned saturation. This patch fixes the logic.
Signed-off-by: Joseph Myers <jos...@codesourcery.com> --- Previous submission: <http://lkml.org/lkml/2013/10/8/694>. I have made the corresponding changes to the glibc/libgcc copy of this code, given that it would be desirable to resync the Linux and glibc/libgcc copies (the latter has had many enhancements and bug fixes since it was copied into Linux), although strictly this incorrect saturation is only a bug when trying to emulate particular instruction semantics, not when used in userspace to implement C operations where the results of out-of-range conversions are unspecified or undefined. diff --git a/include/math-emu/op-common.h b/include/math-emu/op-common.h index 9696a5e..70fe5e9 100644 --- a/include/math-emu/op-common.h +++ b/include/math-emu/op-common.h @@ -685,7 +685,7 @@ do { \ else \ { \ r = 0; \ - if (X##_s) \ + if (!X##_s) \ r = ~r; \ } \ FP_SET_EXCEPTION(FP_EX_INVALID); \ @@ -762,7 +762,7 @@ do { \ if (!rsigned) \ { \ r = 0; \ - if (X##_s) \ + if (!X##_s) \ r = ~r; \ } \ else if (rsigned != 2) \ -- Joseph S. Myers jos...@codesourcery.com _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
