[Bug target/56890] invalid fdtox instruction in 64-bit mode with -O2

[windward at gmx dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56890

--- Comment #6 from Martin <windward at gmx dot com> 2013-04-11 09:21:54 UTC ---
Created attachment 29854
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29854
Results of testcase with -O0 to -O3 for gcc 4.7.2 and 4.8.0

Output (stdout+stderr, assembler file) of Rainer's bigger testcase.

Ran a short testcase with gcc 4.7.2 and 4.8.0, each called with -O0 to -O3.
Other parameters were -m64 -save-temps -Wall -Wextra -fno-strict-aliasing
-fwrapv. Assembler was GNU assembler (GNU Binutils) 2.23.1. More details
available if needed.

gcc 4.8.0 compiles fine except for a warning:

test.c: In function 'buggy':
test.c:6:67: warning: 'num16' may be used uninitialized in this function
[-Wmaybe-uninitialized]
         num16 = min + (long) ((double) (max - min + 1.0) * (num16 / (65535 +
1.0)));
                                                                   ^
test.c:10:71: warning: 'number' may be used uninitialized in this function
[-Wmaybe-uninitialized]
         (number) = min + (long) ((double) (max - min + 1.0) * (number /
(4294967295U + 1.0)));
                                                                       ^
gcc 4.7.2 fails for anything but -O0:

::::::::::::::
gcc472_O0_out
::::::::::::::
test.c: In function 'buggy':
test.c:6:67: warning: 'num16' may be used uninitialized in this function
[-Wuninitialized]
test.c:10:71: warning: 'number' may be used uninitialized in this function
[-Wuninitialized]
::::::::::::::
gcc472_O1_out
::::::::::::::
test.c: In function 'buggy':
test.c:6:67: warning: 'num16' may be used uninitialized in this function
[-Wuninitialized]
test.c:10:71: warning: 'number' may be used uninitialized in this function
[-Wuninitialized]
test.c:13:1: error: insn does not satisfy its constraints:
(insn 127 42 43 3 (set (reg:HI 40 %f8 [162])
        (reg:HI 42 %f10)) test.c:6 58 {*movhi_insn}
     (nil))
test.c:13:1: internal compiler error: in reload_cse_simplify_operands, at
postreload.c:403
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.
::::::::::::::
gcc472_O2_out
::::::::::::::
test.c: In function 'buggy':
test.c:6:67: warning: 'num16' may be used uninitialized in this function
[-Wuninitialized]
test.c:10:71: warning: 'number' may be used uninitialized in this function
[-Wuninitialized]
test.s: Assembler messages:
test.s:35: Error: Illegal operands
::::::::::::::
gcc472_O3_out
::::::::::::::
test.c: In function 'buggy':
test.c:6:67: warning: 'num16' may be used uninitialized in this function
[-Wuninitialized]
test.c:10:71: warning: 'number' may be used uninitialized in this function
[-Wuninitialized]
test.s: Assembler messages:
test.s:35: Error: Illegal operands

Hope that helps.

Cheers,

Martin