Re: toolchain/52660 (gcc on sparc crashes when optimizing)

[Michael <macallan%netbsd.org@localhost>]

The following reply was made to PR toolchain/52660; it has been noted by GNATS.

From: Michael <macallan%netbsd.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: toolchain/52660 (gcc on sparc crashes when optimizing)
Date: Wed, 20 Jun 2018 18:41:39 -0400

 Here's what I get with a userland from a few days ago:
 
 /home/work/benchmarks/flops/work> gcc -DUNIX -O2 -wrapper gdb,--args -o flops flops.c -lm
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 Reading symbols from /usr/libexec/cc1...(no debugging symbols found)...done.
 (gdb) run
 Starting program: /usr/libexec/cc1 -quiet -D UNIX flops.c -quiet -dumpbase flops.c -mcpu=v7 -auxbase flops -O2 -o /var/tmp//ccbu0R7N.s
 flops.c: In function 'main':
 flops.c:226:4: warning: implicit declaration of function 'dtime' [-Wimplicit-function-declaration]
     dtime(TimeArray);
     ^~~~~
 flops.c:641:4: warning: implicit declaration of function 'exit' [-Wimplicit-function-declaration]
     exit(0);
     ^~~~
 flops.c:641:4: warning: incompatible implicit declaration of built-in function 'exit'
 flops.c:641:4: note: include '<stdlib.h>' or provide a declaration of 'exit'
 flops.c: At top level:
 flops.c:719:1: warning: return type defaults to 'int' [-Wimplicit-int]
  dtime(p)
  ^~~~~
 
 Program received signal SIGFPE, Arithmetic exception.
 0xedd059b0 in __divdi3 () from /usr/lib/libgcc_s.so.1
 (gdb) bt
 #0  0xedd059b0 in __divdi3 () from /usr/lib/libgcc_s.so.1
 #1  0x003d2cf0 in sreal::operator/(sreal const&) const ()
 #2  0x00263e4c in estimate_bb_frequencies(bool) ()
 #3  0x00265ea0 in tree_estimate_probability() ()
 #4  0x0026698c in ?? ()
 Backtrace stopped: previous frame identical to this frame (corrupt stack?)
 (gdb) disassemble __divdi3
 Dump of assembler code for function __divdi3:
 ...
    0xedd059a8 <+336>:   nop 
    0xedd059ac <+340>:   udiv  %g1, 0, %g2
 => 0xedd059b0 <+344>:   clr  %g1
    0xedd059b4 <+348>:   wr  %g1, %y
    0xedd059b8 <+352>:   nop 
 ... err, what?
 Ok, my userland was built with -mcpu=hypersparc, so udiv is allowed.
 But that's an explicit division by 0 if I read that correctly.
 How on earth did it get there?
 
 have fun
 Michael