On 2/7/20 8:34 AM, Rogerio Alves wrote:
This patch refactor fenviline.h replaces some statements for
builtins.
---
* Changes in v2: Per Adhemerval review: don not redefine _buitins use a
macro instead. Use of __builtin_popcount allows do eliminate the
if (e == 0) test. __builtin_popcount(e) == 1 for e = 0 validate false
while (e & (e - 1)) == 0 validate true if e = 0. Appended a comment
about the weird asm constrain i#*X. The warning only appear at GCC
versions 3 and below. If we even stops to support GCC 3 for installed
headers we may replace that for plain `i`.
sysdeps/powerpc/bits/fenvinline.h | 30 +++++++++++++++++-------------
1 file changed, 17 insertions(+), 13 deletions(-)
diff --git a/sysdeps/powerpc/bits/fenvinline.h b/sysdeps/powerpc/bits/fenvinline.h
index 70689664e2..7b2b75e5ef 100644
--- a/sysdeps/powerpc/bits/fenvinline.h
+++ b/sysdeps/powerpc/bits/fenvinline.h
@@ -51,9 +51,19 @@
# define fegetround() __fegetround ()
# ifndef __NO_MATH_INLINES
+
+/* Builtins to mtfsb0 and mtfsb1 was introduced on GCC 9. */
+# if !__GNUC_PREREQ(9, 0)
/* The weird 'i#*X' constraints on the following suppress a gcc
warning when __excepts is not a constant. Otherwise, they mean the
- same as just plain 'i'. */
+ same as just plain 'i'. This warning only happens in old GCC
+ versions (gcc 3 or less). Otherwise plain 'i' works fine. */
+# define __mtfsb0(__b) __asm__ __volatile__ ("mtfsb0 %0" : : "i#*X" (__b))
+# define __mtfsb1(__b) __asm__ __volatile__ ("mtfsb1 %0" : : "i#*X" (__b))
+# else
+# define __mtfsb0(__b) __builtin_mtfsb0 (__b)
+# define __mtfsb1(__b) __builtin_mtfsb1 (__b)
+# endif
These names actually conflict with XL compiler builtins which serve the same purpose. https://www.ibm.com/support/knowledgecenter/SSXVZZ_16.1.1/com.ibm.xlcpp1611.lelinux.doc/compiler_ref/bifs_fpscr.html
Maybe all caps? __MTFSB0/__MTFSB1 ?
Of course, I don't think XL currently provides the __builtin versions, so the chances of an actual collision are vanishingly small. I would be nice to plan for better compatibility in the future, though. :-)
PC