Re: [PATCH][AArch64][1/3] PR target/84164: Simplify subreg + redundant AND-immediate

[Kyrill Tkachov]

Ping.

Thanks,
Kyrill

On 19/02/18 11:35, Kyrill Tkachov wrote:

Ping.

https://gcc.gnu.org/ml/gcc-patches/2018-02/msg00649.html

CC'ing Eric and Jeff as the patch contains a simplify-rtx.c component that I'll 
need midend approval on.

Thanks everyone for your comments so far.
Kyrill

On 12/02/18 15:18, Kyrill Tkachov wrote:

Hi Richard,

On 08/02/18 20:29, Richard Sandiford wrote:

Thanks for doing this.

Kyrill  Tkachov <kyrylo.tkac...@foss.arm.com> writes:

diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index 
2e7aa5c12952ab1a9b49b5adaf23710327e577d3..af06d7502cebac03cefc689b2646874b8397e767
 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -6474,6 +6474,18 @@ simplify_subreg (machine_mode outermode, rtx op,
        return NULL_RTX;
      }
  +  /* Simplify (subreg:QI (and:SI (reg:SI) (const_int 0xffff)) 0)
+     into (subreg:QI (reg:SI) 0).  */
+  scalar_int_mode int_outermode, int_innermode;
+  if (!paradoxical_subreg_p (outermode, innermode)
+      && is_a <scalar_int_mode> (outermode, &int_outermode)
+      && is_a <scalar_int_mode> (innermode, &int_innermode)
+      && GET_CODE (op) == AND && CONST_INT_P (XEXP (op, 1))
+      && known_eq (subreg_lowpart_offset (outermode, innermode), byte)
+      && (~INTVAL (XEXP (op, 1)) & GET_MODE_MASK (int_outermode)) == 0
+      && validate_subreg (outermode, innermode, XEXP (op, 0), byte))
+    return gen_rtx_SUBREG (outermode, XEXP (op, 0), byte);
+
    /* A SUBREG resulting from a zero extension may fold to zero if
       it extracts higher bits that the ZERO_EXTEND's source bits.  */
    if (GET_CODE (op) == ZERO_EXTEND && SCALAR_INT_MODE_P (innermode))

I think it'd be better to do this in simplify_truncation (shared
by the subreg code and the TRUNCATE code).  The return would then
be simplify_gen_unary (TRUNCATE, ...), which will become a subreg
if TRULY_NOOP_TRUNCATION.

Thanks, that does look cleaner.
Bootstrapped and tested on arm-none-linux-gnueabihf, aarch64-none-linux-gnu and 
x86_64-unknown-linux-gnu.
The other two patches are still needed to address the fallout.

Is this ok?

Thanks,
Kyrill

2018-02-12  Kyrylo Tkachov  <kyrylo.tkac...@arm.com>

    PR target/84164
    * simplify-rtx.c (simplify_truncation): Simplify truncation of masking
    operation.
    * config/aarch64/aarch64.md (*aarch64_reg_<mode>3_neg_mask2):
    Use simplify_gen_unary creating a SUBREG.
    (*aarch64_reg_<mode>3_minus_mask): Likewise.
    (*aarch64_<optab>_reg_di3_mask2): Use const_int_operand predicate
    for operand 3.

2018-02-12  Kyrylo Tkachov  <kyrylo.tkac...@arm.com>

    PR target/84164
    * gcc.c-torture/compile/pr84164.c: New test.