[committed] aarch64: Extend aarch64-autovec-preference==2 to 128-bit SVE

[committed] aarch64: Extend aarch64-autovec-preference==2 to 128-bit SVE

[Richard Sandiford]

When compiling with -msve-vector-bits=128, aarch64_preferred_simd_mode
would pass the same vector width to aarch64_simd_container_mode for
both SVE and Advanced SIMD, and so Advanced SIMD would always “win”.
This patch instead makes it choose directly between SVE and Advanced
SIMD modes, so that aarch64-autovec-preference==2 and
aarch64-autovec-preference==4 work for this configuration.

(aarch64-autovec-preference shouldn't affect aarch64_simd_container_mode
because that would have an ABI impact for things like GNU vectors.)

Tested on aarch64-linux-gnu (with and without SVE), pushed to trunk.
As Kyrill suggested, I'll backport to GCC 10 too.

Richard


gcc/
	* config/aarch64/aarch64.c (aarch64_preferred_simd_mode): Use
	aarch64_full_sve_mode and aarch64_vq_mode directly, instead of
	going via aarch64_simd_container_mode.
---
 gcc/config/aarch64/aarch64.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 67b4c91dbe4..70ddd70556f 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -17421,10 +17421,11 @@ aarch64_preferred_simd_mode (scalar_mode mode)
 {
   /* Take into account explicit auto-vectorization ISA preferences through
      aarch64_cmp_autovec_modes.  */
-  poly_int64 bits
-    = (TARGET_SVE && aarch64_cmp_autovec_modes (VNx16QImode, V16QImode))
-       ? BITS_PER_SVE_VECTOR : 128;
-  return aarch64_simd_container_mode (mode, bits);
+  if (TARGET_SVE && aarch64_cmp_autovec_modes (VNx16QImode, V16QImode))
+    return aarch64_full_sve_mode (mode).else_mode (word_mode);
+  if (TARGET_SIMD)
+    return aarch64_vq_mode (mode).else_mode (word_mode);
+  return word_mode;
 }
 
 /* Return a list of possible vector sizes for the vectorizer