Hi, I wrote a compiler for brainfuck to x86. The result is quite fast but I was curious if I could tune it even more. So I ran it in callgrind but this resulted in:
folkert@snsv ~/Projects/bf-compiler (master)$ valgrind --tool=callgrind ./test ==77043== Callgrind, a call-graph generating cache profiler ==77043== Copyright (C) 2002-2017, and GNU GPL'd, by Josef Weidendorfer et al. ==77043== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info ==77043== Command: ./test ==77043== ==77043== For interactive control, run 'callgrind_control -h'. vex amd64->IR: unhandled instruction bytes: 0xCD 0x80 0xC3 0x67 0x80 0x3E 0x0 0x74 0x5 0x83 vex amd64->IR: REX=0 REX.W=0 REX.R=0 REX.X=0 REX.B=0 vex amd64->IR: VEX=0 VEX.L=0 VEX.nVVVV=0x0 ESC=NONE vex amd64->IR: PFX.66=0 PFX.F2=0 PFX.F3=0 ==77043== valgrind: Unrecognised instruction at address 0x40274e. ==77043== at 0x40274E: ??? (in /home/folkert/Projects/bf-compiler/test) ==77043== by 0x4020EE: ??? (in /home/folkert/Projects/bf-compiler/test) ==77043== Your program just tried to execute an instruction that Valgrind ==77043== did not recognise. There are two possible reasons for this. ==77043== 1. Your program has a bug and erroneously jumped to a non-code ==77043== location. If you are running Memcheck and you just saw a ==77043== warning about a bad jump, it's probably your program's fault. ==77043== 2. The instruction is legitimate but Valgrind doesn't handle it, ==77043== i.e. it's Valgrind's fault. If you think this is the case or ==77043== you are not sure, please let us know and we'll try to fix it. ==77043== Either way, Valgrind will now raise a SIGILL signal which will ==77043== probably kill your program. ==77043== ==77043== Process terminating with default action of signal 4 (SIGILL) ==77043== Illegal opcode at address 0x40274E ==77043== at 0x40274E: ??? (in /home/folkert/Projects/bf-compiler/test) ==77043== by 0x4020EE: ??? (in /home/folkert/Projects/bf-compiler/test) ==77043== ==77043== Events : Ir ==77043== Collected : 28836 ==77043== ==77043== I refs: 28,836 Illegal instruction (core dumped) If you're curious what is going wrong here, the source assembly and the x86 binary can be retrieved from https://vanheusden.com/permshare/callgrind-error.tar.xz Oh and if you would like to assemble the assembly yourself: as -g mandelbrot.s ld -g a.out -o test ./test then results in the mandelbrot-fractal. Regards, Folkert van Heusden _______________________________________________ Valgrind-users mailing list Valgrind-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/valgrind-users
