On Tue, Aug 8, 2023 at 5:10 AM Pan Li via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> From: Pan Li <pan2...@intel.com>
>
> In same cases, like gcc/testsuite/gcc.dg/pr78148.c in RISC-V, there will
> be only 1 operand when SET_SRC in create_pre_exit. For example as below.
>
> (insn 13 9 14 2 (clobber (reg/i:TI 10 a0))
> "gcc/testsuite/gcc.dg/pr78148.c":24:1 -1
> (expr_list:REG_UNUSED (reg/i:TI 10 a0)
> (nil)))
>
> Unfortunately, SET_SRC requires at least 2 operands and then Segment
> Fault here. This patch would like to fix this ICE by ignoring the USE
> and CLOBBER insn before SET_SRC.
Note I don't think we're supposed to arrive here and it needs more explanation
as to why this is the correct fix to deal with the CLOBBER arriving
here. Simply
making sure to not ICE can lead to wrong-code.
Earlier in the code we make sure to either have a single_set or a CLOBBER:
/* If the return register is not (in its entirety)
likely spilled, the return copy might be
partially or completely optimized away. */
return_copy_pat = single_set (return_copy);
if (!return_copy_pat)
{
return_copy_pat = PATTERN (return_copy);
if (GET_CODE (return_copy_pat) != CLOBBER)
break;
else if (!optimize)
{
/* This might be (clobber (reg [<result>]))
when not optimizing. Then check if
the previous insn is the clobber for
the return register. */
copy_reg = SET_DEST (return_copy_pat);
...
}
copy_reg = SET_DEST (return_copy_pat);
so it looks "wrong" here already (try to enable RTL checking and extra
checking). Well, we have
#define SET_DEST(RTX) XC2EXP (RTX, 0, SET, CLOBBER)
#define SET_SRC(RTX) XCEXP (RTX, 1, SET)
so SET_DEST is fine for CLOBBER, so I suppose the SH4 code is incorrect.
Please check when that was added and why and how that should be made
more correct.
Richard.
> Signed-off-by: Pan Li <pan2...@intel.com>
>
> gcc/ChangeLog:
>
> * mode-switching.cc (create_pre_exit): Add USE and CLOBBER check.
> * rtl.h (CLOBBER_OR_USE_P): New macro.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/riscv/mode-switch-ice-1.c: New test.
> ---
> gcc/mode-switching.cc | 1 +
> gcc/rtl.h | 4 ++++
> .../gcc.target/riscv/mode-switch-ice-1.c | 22 +++++++++++++++++++
> 3 files changed, 27 insertions(+)
> create mode 100644 gcc/testsuite/gcc.target/riscv/mode-switch-ice-1.c
>
> diff --git a/gcc/mode-switching.cc b/gcc/mode-switching.cc
> index 64ae2bc29c3..8bb016a811d 100644
> --- a/gcc/mode-switching.cc
> +++ b/gcc/mode-switching.cc
> @@ -411,6 +411,7 @@ create_pre_exit (int n_entities, int *entity_map, const
> int *num_modes)
> conflict with address reloads. */
> if (copy_start >= ret_start
> && copy_start + copy_num <= ret_end
> + && !CLOBBER_OR_USE_P (return_copy_pat)
> && OBJECT_P (SET_SRC (return_copy_pat)))
> forced_late_switch = true;
> break;
> diff --git a/gcc/rtl.h b/gcc/rtl.h
> index e1c51156f90..cdc2941c210 100644
> --- a/gcc/rtl.h
> +++ b/gcc/rtl.h
> @@ -1768,6 +1768,10 @@ extern const char * const reg_note_name[];
> #define VAR_LOC_UNKNOWN_P(X) \
> (GET_CODE (X) == CLOBBER && XEXP ((X), 0) == const0_rtx)
>
> +/* Determine whether RTX is USE or CLOBBER. */
> +#define CLOBBER_OR_USE_P(RTX) \
> + (GET_CODE (RTX) == USE || GET_CODE (RTX) == CLOBBER)
> +
> /* 1 if RTX is emitted after a call, but it should take effect before
> the call returns. */
> #define NOTE_DURING_CALL_P(RTX) \
> diff --git a/gcc/testsuite/gcc.target/riscv/mode-switch-ice-1.c
> b/gcc/testsuite/gcc.target/riscv/mode-switch-ice-1.c
> new file mode 100644
> index 00000000000..1b34a471904
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/mode-switch-ice-1.c
> @@ -0,0 +1,22 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +
> +struct A { char e, f; };
> +
> +struct B
> +{
> + int g;
> + struct A h[4];
> +};
> +
> +extern void bar (int, int);
> +
> +struct B foo (void)
> +{
> + bar (2, 1);
> +}
> +
> +void baz ()
> +{
> + foo ();
> +}
> --
> 2.34.1
>
