Fix powerpc-nofpu complex long double functions spurious "invalid" exception (bug 22687) [committed]

Message ID alpine.DEB.2.20.1801092235160.21425@digraph.polyomino.org.uk
State New
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  • Fix powerpc-nofpu complex long double functions spurious "invalid" exception (bug 22687) [committed]
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Commit Message

Joseph Myers Jan. 9, 2018, 10:35 p.m.
For soft-float powerpc, various _Complex long double functions
generate spurious "invalid" exceptions, even with a compiler with GCC
bug 64811 fixed.

The problem is GCC's built-in fabsl expansion.  Various files are
already built with -fno-builtin-fabsl because in this case (IBM long
double, for soft-float or e500v1) a fallback fabsl expansion based on
comparisons is used, which can produce the wrong sign of a zero
result.  Those comparisons can also produce spurious exceptions for
NaN arguments.  Furthermore, __builtin_fpclassify implemently uses
__builtin_fabsl, and is unaffected by -fno-builtin-fabsl, and the
fpclassify macro uses __builtin_fpclassify in the absence of
-fsignaling-nans.  Thus, this patch arranges for the problem files
using fpclassify to be built with -fsignaling-nans in this case, to
avoid spurious exceptions from fpclassify.

Tested for powerpc (soft-float).  Committed.

2018-01-09  Joseph Myers  <joseph@codesourcery.com>

	[BZ #22687]
	* sysdeps/powerpc/nofpu/Makefile (CFLAGS-s_cacosl.c): New
	variable.
	(CFLAGS-s_cacoshl.c): Likewise.
	(CFLAGS-s_casinhl.c): Likewise.
	(CFLAGS-s_catanl.c): Likewise.
	(CFLAGS-s_catanhl.c): Likewise.
	(CFLAGS-s_cexpl.c): Likewise.
	(CFLAGS-s_ccoshl.c): Add -fsignaling-nans.
	(CFLAGS-s_csinhl.c): Likewise.
	(CFLAGS-s_clogl.c): Likewise.
	(CFLAGS-s_clog10l.c): Likewise.
	(CFLAGS-s_csinl.c): Likewise.
	(CFLAGS-s_csqrtl.c): Likewise.

Patch

diff --git a/sysdeps/powerpc/nofpu/Makefile b/sysdeps/powerpc/nofpu/Makefile
index ed16321..09ecdf1 100644
--- a/sysdeps/powerpc/nofpu/Makefile
+++ b/sysdeps/powerpc/nofpu/Makefile
@@ -15,15 +15,29 @@  CPPFLAGS += -I../soft-fp/
 # gcc-4.1.1 and may be too late for gcc-4.2.  So we need these flags
 # until the fix in a gcc release and glibc drops support for earlier
 # versions of gcc.
+#
+# This bug can cause wrong signs of zero results from fabsl, and
+# spurious "invalid" exceptions from comparisons with NaN in the
+# default code sequence generated.  The fpclassify expansion used by
+# __builtin_fpclassify, which is used in the absence of
+# -fsignaling-nans, uses __builtin_fabsl, and is not affected by
+# -fno-builtin-fabsl, so requiring -fsignaling-nans for some affected
+# source files.
 CFLAGS-e_atan2l.c += -fno-builtin-fabsl
 CFLAGS-e_hypotl.c += -fno-builtin-fabsl
 CFLAGS-e_powl.c += -fno-builtin-fabsl
-CFLAGS-s_ccoshl.c += -fno-builtin-fabsl
-CFLAGS-s_csinhl.c += -fno-builtin-fabsl
-CFLAGS-s_clogl.c += -fno-builtin-fabsl
-CFLAGS-s_clog10l.c += -fno-builtin-fabsl
-CFLAGS-s_csinl.c += -fno-builtin-fabsl
-CFLAGS-s_csqrtl.c += -fno-builtin-fabsl
+CFLAGS-s_cacosl.c += -fsignaling-nans
+CFLAGS-s_cacoshl.c += -fsignaling-nans
+CFLAGS-s_casinhl.c += -fsignaling-nans
+CFLAGS-s_catanl.c += -fsignaling-nans
+CFLAGS-s_catanhl.c += -fsignaling-nans
+CFLAGS-s_ccoshl.c += -fno-builtin-fabsl -fsignaling-nans
+CFLAGS-s_cexpl.c += -fsignaling-nans
+CFLAGS-s_csinhl.c += -fno-builtin-fabsl -fsignaling-nans
+CFLAGS-s_clogl.c += -fno-builtin-fabsl -fsignaling-nans
+CFLAGS-s_clog10l.c += -fno-builtin-fabsl -fsignaling-nans
+CFLAGS-s_csinl.c += -fno-builtin-fabsl -fsignaling-nans
+CFLAGS-s_csqrtl.c += -fno-builtin-fabsl -fsignaling-nans
 CFLAGS-w_acosl_compat.c += -fno-builtin-fabsl
 CFLAGS-w_asinl_compat.c += -fno-builtin-fabsl
 CFLAGS-w_atanhl_compat.c += -fno-builtin-fabsl