On Wed, 19 Jul 2023, YunQiang Su wrote:
> PR #104914
>
> When work with
> int val;
> ((unsigned char*)&val)[3] = *buf;
> if (val > 0) ...
> The RTX mode is obtained from REG instead of SUBREG, which make
> D<INS> is used instead of <INS>. Thus something wrong happens
> on sign-extend default architectures, like MIPS64.
>
> Let's use str_rtx and mode of str_rtx as the parameters for
> store_integral_bit_field if:
> modes of op0 and str_rtx are INT;
> length of op0 is greater than str_rtx.
>
> This patch has been tested on aarch64-linux-gnu, x86_64-linux-gnu,
> mips64el-linux-gnuabi64 without regression.
I still think you are "fixing" this in the wrong place. The bugzilla
audit trail points to combine and later notes an eventual expansion
issue (but for another testcase/target).
You have to explain in more detail on what is wrong with the initial
RTL on mips.
Richard.
> gcc/ChangeLog:
> PR: 104914.
> * expmed.cc(store_bit_field_1): Pass str_rtx and its mode
> to store_integral_bit_field if the length of op0 is greater
> than str_rtx.
>
> gcc/testsuite/ChangeLog:
> PR: 104914.
> * gcc.target/mips/pr104914.c: New testcase.
> ---
> gcc/expmed.cc | 20 +++++++++++++++++---
> gcc/testsuite/gcc.target/mips/pr104914.c | 17 +++++++++++++++++
> 2 files changed, 34 insertions(+), 3 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/mips/pr104914.c
>
> diff --git a/gcc/expmed.cc b/gcc/expmed.cc
> index fbd4ce2d42f..5531c19e891 100644
> --- a/gcc/expmed.cc
> +++ b/gcc/expmed.cc
> @@ -850,6 +850,7 @@ store_bit_field_1 (rtx str_rtx, poly_uint64 bitsize,
> poly_uint64 bitnum,
> since that case is valid for any mode. The following cases are only
> valid for integral modes. */
> opt_scalar_int_mode op0_mode = int_mode_for_mode (GET_MODE (op0));
> + opt_scalar_int_mode str_mode = int_mode_for_mode (GET_MODE (str_rtx));
> scalar_int_mode imode;
> if (!op0_mode.exists (&imode) || imode != GET_MODE (op0))
> {
> @@ -881,9 +882,22 @@ store_bit_field_1 (rtx str_rtx, poly_uint64 bitsize,
> poly_uint64 bitnum,
> op0 = gen_lowpart (op0_mode.require (), op0);
> }
>
> - return store_integral_bit_field (op0, op0_mode, ibitsize, ibitnum,
> - bitregion_start, bitregion_end,
> - fieldmode, value, reverse, fallback_p);
> + /* If MODEs of str_rtx and op0 are INT, and the length of op0 is greater
> than
> + str_rtx, it means that str_rtx has a shorter SUBREG: int32 on 64
> mach/ABI
> + is an example. For this case, we should use the mode of SUBREG,
> otherwise
> + bad code will generate for sign-extension ports, like MIPS. */
> + bool use_str_mode = false;
> + if (GET_MODE_CLASS (GET_MODE (str_rtx)) == MODE_INT
> + && GET_MODE_CLASS (GET_MODE (op0)) == MODE_INT
> + && known_gt (GET_MODE_SIZE (GET_MODE (op0)),
> + GET_MODE_SIZE (GET_MODE (str_rtx))))
> + use_str_mode = true;
> +
> + return store_integral_bit_field (use_str_mode ? str_rtx : op0,
> + use_str_mode ? str_mode : op0_mode,
> + ibitsize, ibitnum, bitregion_start,
> + bitregion_end, fieldmode, value,
> + reverse, fallback_p);
> }
>
> /* Subroutine of store_bit_field_1, with the same arguments, except
> diff --git a/gcc/testsuite/gcc.target/mips/pr104914.c
> b/gcc/testsuite/gcc.target/mips/pr104914.c
> new file mode 100644
> index 00000000000..fd6ef6af446
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/mips/pr104914.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile } */
> +/* { dg-options "-march=mips64r2 -mabi=64" } */
> +
> +/* { dg-final { scan-assembler-not "\tdins\t" } } */
> +
> +NOMIPS16 int test (const unsigned char *buf)
> +{
> + int val;
> + ((unsigned char*)&val)[0] = *buf++;
> + ((unsigned char*)&val)[1] = *buf++;
> + ((unsigned char*)&val)[2] = *buf++;
> + ((unsigned char*)&val)[3] = *buf++;
> + if(val > 0)
> + return 1;
> + else
> + return 0;
> +}
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg,
Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman;
HRB 36809 (AG Nuernberg)
