Hi,

seen in a segfault running the tests in the coinor-osi package, https://launchpad.net/bugs/1263576, both in saucy and trusty, version 0.106.4 and 0.106.5. Version 0.103 doesn't show the issue.

both the 4.7 and 4.8 linaro branches show this behaviour, and trunk 20131121 (didn't build a newer one yet).

William Grant tracked that down to a bug with very negative vcall_offsets in aarch64 multiple inheritance thunks. The example below has two consecutive thunks, with the second adding 263 instead of subtracting 264. aarch64_build_constant seems to not handle negative integers. He tried a quick gcc patch to avoid using aarch64_build_constant, and the coinor-osi tests succeed.

0000000000401ca4 <_ZTv0_n256_N1C2adEv>: 401ca4: f9400010 ldr x16, [x0] 401ca8: f8500211 ldr x17, [x16,#-256] 401cac: 8b110000 add x0, x0, x17 401cb0: 17fffff9 b 401c94 <_ZN1C2adEv>

[...]

0000000000401cc4 <_ZTv0_n264_N1C2aeEv>: 401cc4: f9400010 ldr x16, [x0] 401cc8: d28020f1 mov x17, #0x107 // #263 401ccc: f8716a11 ldr x17, [x16,x17] 401cd0: 8b110000 add x0, x0, x17 401cd4: 17fffff8 b 401cb4 <_ZN1C2aeEv>

Any chance for a quick 2013 review?

Thanks, Matthias

--- a/gcc/config/aarch64/aarch64.c +++ b/gcc/config/aarch64/aarch64.c @@ -2540,8 +2540,8 @@ addr = plus_constant (Pmode, temp0, vcall_offset); else { - aarch64_build_constant (IP1_REGNUM, vcall_offset); - addr = gen_rtx_PLUS (Pmode, temp0, temp1); + aarch64_add_constant (IP0_REGNUM, IP1_REGNUM, vcall_offset); + addr = temp0; }

aarch64_emit_move (temp1, gen_rtx_MEM (Pmode,addr));