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. -- H.J.
