[PATCH 3/3]AArch64: use movi d0, #0 to clear SVE registers instead of mov z0.d, #0

[Tamar Christina]

Hi All,

This patch changes SVE to use Adv. SIMD fmov 0 to clear SVE registers when not
in SVE streaming mode.  As the Neoverse Software Optimization guides indicate
SVE mov #0 is not a zero cost move.

When In streaming mode we continue to use SVE's mov to clear the registers.

Tests have already been updated.

Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.

Ok for master?

Thanks,
Tamar

gcc/ChangeLog:

        * config/aarch64/aarch64.cc (aarch64_output_sve_mov_immediate): Use
        fmov for SVE zeros.

---
diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 
9142a1eb319c9d596eaa8ab723c5abea60818438..a9d8f9fbeddd0f4269c1671f8d1b504c68ef3910
 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -25515,8 +25515,11 @@ aarch64_output_sve_mov_immediate (rtx const_vector)
        }
     }
 
-  snprintf (templ, sizeof (templ), "mov\t%%0.%c, #" HOST_WIDE_INT_PRINT_DEC,
-           element_char, INTVAL (info.u.mov.value));
+  if (info.u.mov.value == const0_rtx && TARGET_NON_STREAMING)
+    snprintf (templ, sizeof (templ), "movi\t%%d0, #0");
+  else
+    snprintf (templ, sizeof (templ), "mov\t%%0.%c, #" HOST_WIDE_INT_PRINT_DEC,
+             element_char, INTVAL (info.u.mov.value));
   return templ;
 }
 




-- 

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 9142a1eb319c9d596eaa8ab723c5abea60818438..a9d8f9fbeddd0f4269c1671f8d1b504c68ef3910 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -25515,8 +25515,11 @@ aarch64_output_sve_mov_immediate (rtx const_vector)
 	}
     }
 
-  snprintf (templ, sizeof (templ), "mov\t%%0.%c, #" HOST_WIDE_INT_PRINT_DEC,
-	    element_char, INTVAL (info.u.mov.value));
+  if (info.u.mov.value == const0_rtx && TARGET_NON_STREAMING)
+    snprintf (templ, sizeof (templ), "movi\t%%d0, #0");
+  else
+    snprintf (templ, sizeof (templ), "mov\t%%0.%c, #" HOST_WIDE_INT_PRINT_DEC,
+	      element_char, INTVAL (info.u.mov.value));
   return templ;
 }