On 10 December 2013 21:51, H.J. Lu <hjl.to...@gmail.com> wrote: > On Tue, Dec 10, 2013 at 1:09 PM, H.J. Lu <hjl.to...@gmail.com> wrote: >> On Tue, Dec 10, 2013 at 12:39 PM, Richard Henderson <r...@redhat.com> wrote: >>> On 12/10/2013 10:44 AM, Richard Sandiford wrote: >>>> Sorry, I don't understand. I never said it was invalid. I said >>>> (subreg:SF (reg:V4SF X) 1) was invalid if (reg:V4SF X) represents >>>> a single register. On a little-endian target, the offset cannot be >>>> anything other than 0 in that case. >>>> >>>> So the CANNOT_CHANGE_MODE_CLASS code above seems to be checking for >>>> something that is always invalid, regardless of the target. That kind >>>> of situation should be rejected by target-independent code instead. >>> >>> But, we want to disable the subreg before we know whether or not (reg:V4SF >>> X) >>> will be allocated to a single hard register. That is something that we >>> can't >>> know in target-independent code before register allocation. >> >> I tried Kirill's patch. But LRA isn't prepared to handle it: >> >> spawn -ignore SIGHUP /export/build/gnu/gcc/build-x86_64-linux/gcc/xgcc >> -B/export/build/gnu/gcc/build-x86_64-linux/gcc/ >> /export/gnu/import/git/gcc/gcc/testsuite/gcc.dg/atomic/c11-atomic-exec-1.c >> -B/export/build/gnu/gcc/build-x86_64-linux/x86_64-unknown-linux-gnu/32/libatomic/ >> -L/export/build/gnu/gcc/build-x86_64-linux/x86_64-unknown-linux-gnu/32/libatomic/.libs >> -latomic -fno-diagnostics-show-caret -fdiagnostics-color=never -O1 >> -std=c11 -pedantic-errors -lm -m32 -o ./c11-atomic-exec-1.exe^M >> /export/gnu/import/git/gcc/gcc/testsuite/gcc.dg/atomic/c11-atomic-exec-1.c: >> In function 'test_simple_assign':^M >> /export/gnu/import/git/gcc/gcc/testsuite/gcc.dg/atomic/c11-atomic-exec-1.c:81:1: >> internal compiler error: Maximum number of LRA constraint passes is >> achieved (30)^M >> ^M >> 0x88ed77 lra_constraints(bool)^M >> /export/gnu/import/git/gcc/gcc/lra-constraints.c:3871^M >> 0x87fe8c lra(_IO_FILE*)^M >> /export/gnu/import/git/gcc/gcc/lra.c:2331^M >> 0x840f76 do_reload^M >> /export/gnu/import/git/gcc/gcc/ira.c:5455^M >> 0x840f76 rest_of_handle_reload^M >> /export/gnu/import/git/gcc/gcc/ira.c:5584^M >> 0x840f76 execute^M >> /export/gnu/import/git/gcc/gcc/ira.c:5613^M >> > > I got several hundred failures like this in GCC > testsuite with -m32 and -m64 on Linux/x86-64. >
I think this is the same as: http://gcc.gnu.org/ml/gcc/2013-12/msg00086.html LRA does not seem to know how to resolve subregs with non-zero offsets that don't map to a full-hardreg. Thanks, Tejas.
