[PATCH v2] aarch64: Add --param=aarch64-autovec-mode

[Alfie Richards]

Allows forcing the autovec mode for testing and debugging purposes.

gcc/ChangeLog:

        * config/aarch64/aarch64.cc (aarch64_autovectorize_vector_modes):
        All logic to only use aarch64-autovec-mode when specified.
        * config/aarch64/aarch64.opt: Add --param=aarch64-autovec-mode.
        * doc/params.texi: Document  --param=aarch64-autovec-mode.
---
 gcc/config/aarch64/aarch64.cc  |  6 ++++++
 gcc/config/aarch64/aarch64.opt | 34 ++++++++++++++++++++++++++++++++++
 gcc/doc/params.texi            |  4 ++++
 3 files changed, 44 insertions(+)

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 107271b0404..6693cec98bd 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -24187,6 +24187,12 @@ aarch64_autovectorize_vector_modes (vector_modes 
*modes, bool)
     V2SImode
   };
 
+  if (aarch64_force_autovec_mode != VOIDmode)
+    {
+      modes->safe_push (aarch64_force_autovec_mode);
+      return 0;
+    }
+
   /* Try using N-byte SVE modes only after trying N-byte Advanced SIMD mode.
      This is because:
 
diff --git a/gcc/config/aarch64/aarch64.opt b/gcc/config/aarch64/aarch64.opt
index deccc6c8887..6f22e0e7326 100644
--- a/gcc/config/aarch64/aarch64.opt
+++ b/gcc/config/aarch64/aarch64.opt
@@ -406,6 +406,40 @@ Enum(aarch64_autovec_preference) String(prefer-asimd) 
Value(AARCH64_AUTOVEC_PREF
 EnumValue
 Enum(aarch64_autovec_preference) String(prefer-sve) 
Value(AARCH64_AUTOVEC_PREFER_SVE)
 
+-param=aarch64-autovec-mode=
+Target Joined Var(aarch64_force_autovec_mode) Enum(aarch64_autovec_mode) 
Init(VOIDmode) Param
+Force a specific mode to be the only one considered for auto vectorization.
+
+If this is specified in addition to --param=aarch64-autovec-preference or
+-mautovec-preference then this takes priority.
+
+Enum
+Name(aarch64_autovec_mode) Type(machine_mode) UnknownError(unknown machine 
mode %qs)
+
+EnumValue
+Enum(aarch64_autovec_mode) String(VNx16QI) Value(VNx16QImode)
+
+EnumValue
+Enum(aarch64_autovec_mode) String(VNx8QI) Value(VNx8QImode)
+
+EnumValue
+Enum(aarch64_autovec_mode) String(VNx4QI) Value(VNx4QImode)
+
+EnumValue
+Enum(aarch64_autovec_mode) String(VNx2QI) Value(VNx2QImode)
+
+EnumValue
+Enum(aarch64_autovec_mode) String(V16QI) Value(V16QImode)
+
+EnumValue
+Enum(aarch64_autovec_mode) String(V8QI) Value(V8QImode)
+
+EnumValue
+Enum(aarch64_autovec_mode) String(V4QI) Value(V4QImode)
+
+EnumValue
+Enum(aarch64_autovec_mode) String(V2QI) Value(V2QImode)
+
 -param=aarch64-loop-vect-issue-rate-niters=
 Target Joined UInteger Var(aarch64_loop_vect_issue_rate_niters) Init(6) 
IntegerRange(0, 65536) Param
 
diff --git a/gcc/doc/params.texi b/gcc/doc/params.texi
index e69be2d2923..8d8e5926cb1 100644
--- a/gcc/doc/params.texi
+++ b/gcc/doc/params.texi
@@ -2027,6 +2027,10 @@ An old alias for @option{-mautovec-preference}.  If both
 @option{-mautovec-preference} and @option{--param=aarch64-autovec-preference}
 are passed, the @option{--param} value is used.
 
+@paindex aarch64-autovec-mode
+@item aarch64-autovec-preference
+Force a specific mode to be the only one considered for auto vectorization.
+
 @paindex aarch64-ldp-policy
 @item aarch64-ldp-policy
 Fine-grained policy for load pair (@code{stp}) instructions.
-- 
2.55.0