When compiling a testbench program using -O2 optimization, the GCC MIPS cross-compiler generates an incorrect instruction sequence (a store before a load to the same memory location) which leads to a memory corruption problem and crashes the program. If the -O1 or -O0 switches are used, this problem does not occur. The output of the gcc -v -save-temps command is included below and the test.i file is attached. I am also including, below, the portion of assembly code that contains the erroneous instruction sequence (see arrows). /mnt/disk/home/tools/mipsel/bin/mipsel-linux-gcc -v -save-temps -O2 -static -DSPEC_CPU_LINUX_IA32 test.o -lm -o perlbench Using built-in specs. Target: mipsel-linux Configured with: ../../src/gcc-4.4.3/configure --target=mipsel-linux --prefix=/mnt/disk/home/tools/mipsel --with-sysroot=/mnt/disk/home/tools/mipsel --disable-libssp --disable-libgomp --disable-libmudflap --disable-nls --enable-languages=c,c++,fortran Thread model: posix gcc version 4.4.3 (GCC) COMPILER_PATH=/mnt/disk/home/tools/mipsel/libexec/gcc/mipsel-linux/4.4.3/:/mnt/disk/home/tools/mipsel/libexec/gcc/mipsel-linux/4.4.3/:/mnt/disk/home/tools/mipsel/libexec/gcc/mipsel-linux/:/mnt/disk/home/tools/mipsel/lib/gcc/mipsel-linux/4.4.3/:/mnt/disk/home/tools/mipsel/lib/gcc/mipsel-linux/:/mnt/disk/home/tools/mipsel/lib/gcc/mipsel-linux/4.4.3/../../../../mipsel-linux/bin/ LIBRARY_PATH=/mnt/disk/home/tools/mipsel/lib/gcc/mipsel-linux/4.4.3/:/mnt/disk/home/tools/mipsel/lib/gcc/mipsel-linux/4.4.3/../../../../mipsel-linux/lib/:/mnt/disk/home/tools/mipsel/lib/:/mnt/disk/home/tools/mipsel/usr/lib/ COLLECT_GCC_OPTIONS='-v' '-save-temps' '-O2' '-static' '-DSPEC_CPU_LINUX_IA32' '-o' 'perlbench' '-mllsc' '-mno-shared' /mnt/disk/home/tools/mipsel/libexec/gcc/mipsel-linux/4.4.3/collect2 --sysroot=/mnt/disk/home/tools/mipsel -EL -static -o perlbench /mnt/disk/home/tools/mipsel/usr/lib/crt1.o /mnt/disk/home/tools/mipsel/usr/lib/crti.o /mnt/disk/home/tools/mipsel/lib/gcc/mipsel-linux/4.4.3/crtbeginT.o -L/mnt/disk/home/tools/mipsel/lib/gcc/mipsel-linux/4.4.3 -L/mnt/disk/home/tools/mipsel/lib/gcc/mipsel-linux/4.4.3/../../../../mipsel-linux/lib -L/mnt/disk/home/tools/mipsel/lib -L/mnt/disk/home/tools/mipsel/usr/lib test.o -lm --start-group -lgcc -lgcc_eh -lc --end-group /mnt/disk/home/tools/mipsel/lib/gcc/mipsel-linux/4.4.3/crtend.o /mnt/disk/home/tools/mipsel/usr/lib/crtn.o /mnt/disk/home/tools/mipsel/usr/lib/crt1.o: In function `__start': >>>>>>>>>>>>>>>>>>>>>>> assembly code >>>>>>>>>>>>>>>>>>>> $L100: lw $3,%got(PL_xiv_root)($28) lw $2,0($16) lw $5,0($3) addiu $4,$2,12 >>>> sw $5,12($2) >>>> lw $19,12($2) li $2,2 # 0x2 beq $17,$2,$L184 sw $4,0($3) beq $18,$0,$L111 nop move $20,$0 move $21,$0 move $18,$0
Created attachment 24384 [details] preprocessed file
Created attachment 24385 [details] assembly language file
I think you have an aliasing problem in your code.
(In reply to comment #3) > I think you have an aliasing problem in your code. The code I am compiling is the Perlbench benchmark from SPEC-CPU2006. If I compile the code for an Intel machine using -O2 there is no problem. This problem only appears when I use the GCC MIPS cross-compiler with the -O2 switch. I also traced through the code and the sequence of these two instructions should be reversed.
(In reply to hanib from comment #4) > (In reply to comment #3) > > I think you have an aliasing problem in your code. > > The code I am compiling is the Perlbench benchmark from SPEC-CPU2006. If I > compile the code for an Intel machine using -O2 there is no problem. This > problem only appears when I use the GCC MIPS cross-compiler with the -O2 > switch. I also traced through the code and the sequence of these two > instructions should be reversed. Perl in SPEC CPU 2006 has known aliasing bugs in it; just use -fno-strict-aliasing.