On Mon, Jan 02, 2017 at 03:47:43PM +0100, Georg-Johann Lay wrote:
> This fixes PR78883 which is a problem in reload revealed by a
> change to combine.c. The fix is as proposed by Segher: implement
> CANNOT_CHANGE_MODE_CLASS.
>
> Ok for trunk?
>
> Johann
>
>
> gcc/
> PR target/78883
> * config/avr/avr.h (CANNOT_CHANGE_MODE_CLASS): New define.
> * config/avr/avr-protos.h (avr_cannot_change_mode_class): New proto.
> * config/avr/avr.c (avr_cannot_change_mode_class): New function.
>
> gcc/testsuite/
> PR target/78883
> * gcc.c-torture/compile/pr78883.c: New test.
> Index: config/avr/avr-protos.h
> ===================================================================
> --- config/avr/avr-protos.h (revision 244001)
> +++ config/avr/avr-protos.h (working copy)
> @@ -111,7 +111,7 @@ extern int _reg_unused_after (rtx_insn *
> extern int avr_jump_mode (rtx x, rtx_insn *insn);
> extern int test_hard_reg_class (enum reg_class rclass, rtx x);
> extern int jump_over_one_insn_p (rtx_insn *insn, rtx dest);
> -
> +extern int avr_cannot_change_mode_class (machine_mode, machine_mode, enum
> reg_class);
> extern int avr_hard_regno_mode_ok (int regno, machine_mode mode);
> extern void avr_final_prescan_insn (rtx_insn *insn, rtx *operand,
> int num_operands);
> Index: config/avr/avr.c
> ===================================================================
> --- config/avr/avr.c (revision 244001)
> +++ config/avr/avr.c (working copy)
> @@ -11833,6 +11833,21 @@ jump_over_one_insn_p (rtx_insn *insn, rt
> }
>
>
> +/* Worker function for `CANNOT_CHANGE_MODE_CLASS'. */
> +
> +int
> +avr_cannot_change_mode_class (machine_mode from, machine_mode to,
> + enum reg_class /* rclass */)
> +{
> + /* We cannot access a hard register in a wider mode, for example we
> + must not access (reg:QI 31) as (reg:HI 31). HARD_REGNO_MODE_OK
> + would avoid such hard regs, but reload would generate it anyway
> + from paradoxical subregs of mem, cf. PR78883. */
> +
> + return GET_MODE_SIZE (to) > GET_MODE_SIZE (from);
I understand how this fixes the ICE, but is it really necessary to
suppress conversions to a wider mode for lower numbered registers?
> +}
> +
> +
> /* Worker function for `HARD_REGNO_MODE_OK'. */
> /* Returns 1 if a value of mode MODE can be stored starting with hard
> register number REGNO. On the enhanced core, anything larger than
> Index: config/avr/avr.h
> ===================================================================
> --- config/avr/avr.h (revision 244001)
> +++ config/avr/avr.h (working copy)
> @@ -216,6 +216,9 @@ These two properties are reflected by bu
>
> #define MODES_TIEABLE_P(MODE1, MODE2) 1
>
> +#define CANNOT_CHANGE_MODE_CLASS(MFROM, MTO, RCLASS) \
> + avr_cannot_change_mode_class (MFROM, MTO, RCLASS)
> +
> enum reg_class {
> NO_REGS,
> R0_REG, /* r0 */
> Index: testsuite/gcc.c-torture/compile/pr78883.c
> ===================================================================
> --- testsuite/gcc.c-torture/compile/pr78883.c (nonexistent)
> +++ testsuite/gcc.c-torture/compile/pr78883.c (working copy)
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +
> +int foo (int *p)
> +{
> + int i;
> + for (i = 0; i < 5; i++)
> + {
> + if (p[i] & 1)
> + return i;
> + }
> + return -1;
> +}
Ciao
Dominik ^_^ ^_^
--
Dominik Vogt
IBM Germany
