Re: [GCC][PATCH][Aarch64] Stop redundant zero-extension after UMOV when in DI mode

[Sudakshina Das <sudi.das@arm.com>]

Hi Sam


On Monday 23 July 2018 11:39 AM, Sam Tebbs wrote:
> Hi all,
>
> This patch extends the aarch64_get_lane_zero_extendsi instruction 
> definition to
> also cover DI mode. This prevents a redundant AND instruction from being
> generated due to the pattern failing to be matched.
>
> Example:
>
> typedef char v16qi __attribute__ ((vector_size (16)));
>
> unsigned long long
> foo (v16qi a)
> {
>   return a[0];
> }
>
> Previously generated:
>
> foo:
>         umov    w0, v0.b[0]
>         and     x0, x0, 255
>         ret
>
> And now generates:
>
> foo:
>         umov    w0, v0.b[0]
>         ret
>
> Bootstrapped on aarch64-none-linux-gnu and tested on aarch64-none-elf 
> with no
> regressions.
>
> gcc/
> 2018-07-23  Sam Tebbs <sam.tebbs@arm.com>
>
>         * config/aarch64/aarch64-simd.md
>     (*aarch64_get_lane_zero_extendsi<mode>):
>         Rename to...
> (*aarch64_get_lane_zero_extend<mode><VDQQH:mode>): ... This.
>         Use GPI iterator instead of SI mode.
>
> gcc/testsuite
> 2018-07-23  Sam Tebbs <sam.tebbs@arm.com>
>
>         * gcc.target/aarch64/extract_zero_extend.c: New file
>
You will need an approval from a maintainer, but I would only add one 
request to this:

diff --git a/gcc/config/aarch64/aarch64-simd.md 
b/gcc/config/aarch64/aarch64-simd.md
index 89e38e6..15fb661 100644
--- a/gcc/config/aarch64/aarch64-simd.md
+++ b/gcc/config/aarch64/aarch64-simd.md
@@ -3032,15 +3032,16 @@
    [(set_attr "type" "neon_to_gp<q>")]
  )

-(define_insn "*aarch64_get_lane_zero_extendsi<mode>"
-  [(set (match_operand:SI 0 "register_operand" "=r")
-    (zero_extend:SI
+(define_insn "*aarch64_get_lane_zero_extend<mode><VDQQH:mode>"
+  [(set (match_operand:GPI 0 "register_operand" "=r")
+    (zero_extend:GPI

Since you are adding 4 new patterns with this change, could you add
more cases in your test as well to make sure you have coverage for each 
of them.

Thanks
Sudi

        (vec_select:<VEL>
          (match_operand:VDQQH 1 "register_operand" "w")
          (parallel [(match_operand:SI 2 "immediate_operand" "i")]))))]
    "TARGET_SIMD"
    {
-    operands[2] = aarch64_endian_lane_rtx (<MODE>mode, INTVAL 
(operands[2]));
+    operands[2] = aarch64_endian_lane_rtx (<VDQQH:MODE>mode,
+                       INTVAL (operands[2]));
      return "umov\\t%w0, %1.<Vetype>[%2]";
    }
    [(set_attr "type" "neon_to_gp<q>")]