http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55145
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|target |middle-end
Summary|[4.8 Regression] [x32] |Different bits for long
|-maddress-mode=long |double constant depending
|miscompiles glibc |ptr_mode
--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> 2012-11-04 08:11:01
UTC ---
GCC i386 and GCC x86-64 generate different bits long double constant
depending ptr_mode:
[hjl@gnu-tools-1 tmp]$ cat y.c
const long double
pio2_hi = 1.5707963267948966192021943710788178805159986950457096099853515625L;
[hjl@gnu-tools-1 tmp]$ /usr/gcc-4.7.3-32bit/bin/gcc -S y.c -o 32.s
[hjl@gnu-tools-1 tmp]$ gcc -S y.c -o 64.s
[hjl@gnu-tools-1 tmp]$ diff -up 64.s 32.s
--- 64.s 2012-11-04 01:06:52.492398183 -0700
+++ 32.s 2012-11-04 01:06:47.685344002 -0700
@@ -3,11 +3,10 @@
.section .rodata
.align 16
.type pio2_hi, @object
- .size pio2_hi, 16
+ .size pio2_hi, 12
pio2_hi:
- .long 560513588
- .long 3373259426
+ .long 560513589
+ .long -921707870
.long 16383
- .long 0
- .ident "GCC: (GNU) 4.7.2 20120921 (Red Hat 4.7.2-2)"
+ .ident "GCC: (GNU) 4.7.3 20121024 (prerelease)"
.section .note.GNU-stack,"",@progbits
[hjl@gnu-tools-1 tmp]$ gcc -c 32.s 64.s
[hjl@gnu-tools-1 tmp]$ objdump -s -j .rodata 32.o > 32
[hjl@gnu-tools-1 tmp]$ objdump -s -j .rodata 64.o > 64
[hjl@gnu-tools-1 tmp]$ diff -up 32 64
--- 32 2012-11-04 01:07:37.341913094 -0700
+++ 64 2012-11-04 01:07:42.192979572 -0700
@@ -1,5 +1,5 @@
-32.o: file format elf64-x86-64
+64.o: file format elf64-x86-64
Contents of section .rodata:
- 0000 35c26821 a2da0fc9 ff3f0000 5.h!.....?..
+ 0000 34c26821 a2da0fc9 ff3f0000 00000000 4.h!.....?......
[hjl@gnu-tools-1 tmp]$
Ignore padding, i386 GCC generates 35c26821 and
x86-64 generates 34c26821.
