On Tue, Apr 15, 2014 at 1:53 PM, Richard Sandiford <rdsandif...@googlemail.com> wrote: > As Robert pointed out here: > > http://gcc.gnu.org/ml/gcc-patches/2014-04/msg00416.html > > we're a bit too eager when folding stuff into an 'X' constraint. > The value at expand time is sensible, but after that asm_operand_ok > allows arbitrary rtx expressions, including any number of registers > as well as MEMs with unchecked addresses. > > This is a target-independent problem, as shown by the testcase below. > Reload would give bogus "impossible constraint in asm" errors > while LRA ICEs. > > Tested on x86_64-linux-gnu. OK to install?
AARCH64 ran into something similar and we did a similar patch though rejecting only mems which are invalid: http://gcc.gnu.org/ml/gcc-patches/2012-12/msg00765.html (http://gcc.gnu.org/ml/gcc-patches/2013-01/msg01128.html) Thanks, Andrew Pinski > > Thanks, > Richard > > > gcc/ > * recog.c (asm_operand_ok): Tighten MEM validity for 'X'. > > gcc/testsuite/ > * gcc.dg/torture/asm-x-constraint-1.c: New test. > > Index: gcc/recog.c > =================================================================== > --- gcc/recog.c 2014-04-12 22:43:54.729854903 +0100 > +++ gcc/recog.c 2014-04-15 21:47:32.139873570 +0100 > @@ -1840,7 +1840,17 @@ asm_operand_ok (rtx op, const char *cons > break; > > case 'X': > - result = 1; > + /* Although the asm itself doesn't impose any restrictions on > + the operand, we still need to restrict it to something that > + can be reloaded and printed. > + > + MEM operands are always reloaded to make them legitimate, > + regardless of the constraint, so we need to handle them > + in the same way as for 'm' and 'g'. Since 'X' is not treated > + as an address constraint, the only other valid operand types > + are constants and registers. */ > + result = (CONSTANT_P (op) > + || general_operand (op, VOIDmode)); > break; > > case 'g': > Index: gcc/testsuite/gcc.dg/torture/asm-x-constraint-1.c > =================================================================== > --- /dev/null 2014-04-15 08:10:27.294524132 +0100 > +++ gcc/testsuite/gcc.dg/torture/asm-x-constraint-1.c 2014-04-15 > 19:11:29.830962008 +0100 > @@ -0,0 +1,27 @@ > +void > +noprop1 (int **x, int y, int z) > +{ > + int *ptr = *x + y * z / 11; > + __asm__ __volatile__ ("noprop1 %0" : : "X" (*ptr)); > +} > + > +void > +noprop2 (int **x, int y, int z) > +{ > + int *ptr = *x + y * z / 11; > + __asm__ __volatile__ ("noprop2 %0" : : "X" (ptr)); > +} > + > +int *global_var; > + > +void > +const1 (void) > +{ > + __asm__ __volatile__ ("const1 %0" : : "X" (global_var)); > +} > + > +void > +const2 (void) > +{ > + __asm__ __volatile__ ("const2 %0" : : "X" (*global_var)); > +}
