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
