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

[Kyrill Tkachov]

On 02/03/18 17:34, Jeff Law wrote:

On 03/01/2018 08:19 AM, Kyrill Tkachov wrote:

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.

Sorry.  I suspect I dropped this from my inbox when it had the AArch64
marker -- I didn't realize it had a target independent component.

The simplify-rtx bits are fine.  The version in simplify_truncation is
much better than the original in simplify_subreg (which I think needed
to verify that you were looking at the lowpart before optimizing).

Thanks Jeff,

I'd like to ask for approval for the aarch64 parts as well from the maintainers.

Kyrill

jeff