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| author | Joseph Myers <joseph@codesourcery.com> | 2014-10-09 01:00:41 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2014-10-09 01:00:41 +0000 |
| commit | 43059f42dbd6dd3926c33ee0cbc7583f0c3e84b9 (patch) | |
| tree | 49c139b7c42576c9b0a4fb3b25424761f37ed8c6 /ChangeLog | |
| parent | 2d6a47ba4ca899746db7fb5ba75a82f2cda93a91 (diff) | |
| download | glibc-43059f42dbd6dd3926c33ee0cbc7583f0c3e84b9.tar.gz glibc-43059f42dbd6dd3926c33ee0cbc7583f0c3e84b9.tar.xz glibc-43059f42dbd6dd3926c33ee0cbc7583f0c3e84b9.zip | |
soft-fp: Make extensions of subnormals from XFmode to TFmode signal underflow if traps enabled.
This patch fixes a soft-fp corner case I previously noted in <https://sourceware.org/ml/libc-alpha/2013-10/msg00349.html>: when trapping on underflow is enabled, extensions of subnormals from XFmode to TFmode need to signal underflow because the result is tiny (but exact, so the underflow flag is not raised unless trapping is enabled). To avoid any excess initialization or tests for other cases of floating-point extensions, a new FP_INIT_TRAPPING_EXCEPTIONS is added that does the initialization required for this particular case (more than FP_INIT_EXCEPTIONS, less than FP_INIT_ROUNDMODE, in general), and FP_NO_EXACT_UNDERFLOW is added to stub out FP_TRAPPING_EXCEPTIONS tests for those cases of extensions where the test would be dead code, to avoid any uninitialized variable warnings. As the relevant case only applies in libgcc, not to any use of soft-fp in glibc, there is no bug report in Bugzilla and no non-default definitions of FP_INIT_TRAPPING_EXCEPTIONS are added by the patch. A testcase will be added to GCC as part of an update of soft-fp in libgcc once this patch is in libc. Tested for powerpc-nofpu that the disassembly of installed shared libraries is unchanged by this patch. Bootstrapped GCC with updated soft-fp with no regressions on x86_64-unknown-linux-gnu and verified that a test of the relevant case passes where it failed before. * soft-fp/op-common.h (FP_EXTEND): When a subnormal input produces a subnormal result, set the underflow exception if trapping on underflow is enabled. * soft-fp/soft-fp.h (FP_INIT_TRAPPING_EXCEPTIONS): New macro. (FP_INIT_EXCEPTIONS): Default to FP_INIT_TRAPPING_EXCEPTIONS. [FP_NO_EXACT_UNDERFLOW] (FP_TRAPPING_EXCEPTIONS): Undefine and redefine to 0. * soft-fp/extenddftf2.c (FP_NO_EXACT_UNDERFLOW): Define. * soft-fp/extendsfdf2.c (FP_NO_EXACT_UNDERFLOW): Likewise. * soft-fp/extendsftf2.c (FP_NO_EXACT_UNDERFLOW): Likewise. * soft-fp/extendxftf2.c (__extendxftf2): Use FP_INIT_TRAPPING_EXCEPTIONS instead of FP_INIT_ROUNDMODE.
Diffstat (limited to 'ChangeLog')
| -rw-r--r-- | ChangeLog | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/ChangeLog b/ChangeLog index b5faff4fe7..703934d098 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,18 @@ 2014-10-09 Joseph Myers <joseph@codesourcery.com> + * soft-fp/op-common.h (FP_EXTEND): When a subnormal input produces + a subnormal result, set the underflow exception if trapping on + underflow is enabled. + * soft-fp/soft-fp.h (FP_INIT_TRAPPING_EXCEPTIONS): New macro. + (FP_INIT_EXCEPTIONS): Default to FP_INIT_TRAPPING_EXCEPTIONS. + [FP_NO_EXACT_UNDERFLOW] (FP_TRAPPING_EXCEPTIONS): Undefine and + redefine to 0. + * soft-fp/extenddftf2.c (FP_NO_EXACT_UNDERFLOW): Define. + * soft-fp/extendsfdf2.c (FP_NO_EXACT_UNDERFLOW): Likewise. + * soft-fp/extendsftf2.c (FP_NO_EXACT_UNDERFLOW): Likewise. + * soft-fp/extendxftf2.c (__extendxftf2): Use + FP_INIT_TRAPPING_EXCEPTIONS instead of FP_INIT_ROUNDMODE. + * soft-fp/soft-fp.h (FP_CLEAR_EXCEPTIONS): Remove macro. * sysdeps/sparc/sparc32/soft-fp/q_itoq.c: Define FP_NO_EXCEPTIONS. (_Q_itoq): Do not use FP_DECL_EX, FP_CLEAR_EXCEPTIONS or |