On Fri, Jan 30, 2015 at 1:57 AM, Alan Modra <amo...@gmail.com> wrote: > On Fri, Jan 16, 2015 at 08:12:27PM +1030, Alan Modra wrote: >> https://lists.ozlabs.org/pipermail/linuxppc-dev/2014-December/123776.html >> shows gcc-5 miscompiling a powerpc64 linux kernel. The executive >> summary is that the rs6000 backend has a bug in its RTL description of >> indirect calls. We specify a parallel containing both the actual call >> and an action that happens after the call, the restore of r2. The >> restore is simply a memory load: >> (set (reg:DI 2 2) >> (mem/v/c:DI (plus:DI (reg/f:DI 1 1) >> (const_int 40 [0x28])) [0 S8 A8])) >> This leads to cprop concluding that it is valid to replace the >> reference to r1 with another register having the same value before the >> call. Unfortunately, sometimes a call-clobbered register is chosen. > > This is the rs6000 backend fix. Bootstrapped etc. powerpc64-linux. > OK to apply? > > gcc/ > * config/rs6000/rs6000.c (rs6000_call_aix): Use unspec rather > than mem for toc_restore. > * config/rs6000/rs6000.md (UNSPEC_TOCSLOT): Define.
Please insert UNSPEC_TOCSLOT in the UNSPEC list after UNSPEC_TOCPTR and UNSPEC_TOC and add a short comment like the other two. > (call_indirect_aix, call_value_indirect_aix): Adjust to suit. > (call_indirect_elfv2, call_value_indirect_elfv2): Likewise. > gcc/testsuite/ > * gcc.target/powerpc/cprophard.c: New. Okay with that change. Thanks, David
