omp-simd-clone: Allow fixed-lane vectors

The vecsize_int/vecsize_float has an assumption that all arguments will use
the same bitsize, and vary the number of lanes according to the element size,
but this is inappropriate on targets where the number of lanes is fixed and
the bitsize varies (i.e. amdgcn).

With this change the vecsize can be left zero and the vectorization factor will
be the same for all types.

gcc/ChangeLog:

	* doc/tm.texi: Regenerate.
	* omp-simd-clone.cc (simd_clone_adjust_return_type): Allow zero
	vecsize.
	(simd_clone_adjust_argument_types): Likewise.
	* target.def (compute_vecsize_and_simdlen): Document the new
	vecsize_int and vecsize_float semantics.

diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 92bda1a7e14..c3001c6ded9 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -6253,6 +6253,9 @@ stores.
 This hook should set @var{vecsize_mangle}, @var{vecsize_int}, @var{vecsize_float}
 fields in @var{simd_clone} structure pointed by @var{clone_info} argument and also
 @var{simdlen} field if it was previously 0.
+@var{vecsize_mangle} is a marker for the backend only. @var{vecsize_int} and
+@var{vecsize_float} should be left zero on targets where the number of lanes is
+not determined by the bitsize (in which case @var{simdlen} is always used).
 The hook should return 0 if SIMD clones shouldn't be emitted,
 or number of @var{vecsize_mangle} variants that should be emitted.
 @end deftypefn
diff --git a/gcc/omp-simd-clone.cc b/gcc/omp-simd-clone.cc
index 58bd68b129b..68ee4c2c3b0 100644
--- a/gcc/omp-simd-clone.cc
+++ b/gcc/omp-simd-clone.cc
@@ -504,7 +504,10 @@ simd_clone_adjust_return_type (struct cgraph_node *node)
     veclen = node->simdclone->vecsize_int;
   else
     veclen = node->simdclone->vecsize_float;
-  veclen = exact_div (veclen, GET_MODE_BITSIZE (SCALAR_TYPE_MODE (t)));
+  if (known_eq (veclen, 0))
+    veclen = node->simdclone->simdlen;
+  else
+    veclen = exact_div (veclen, GET_MODE_BITSIZE (SCALAR_TYPE_MODE (t)));
   if (multiple_p (veclen, node->simdclone->simdlen))
     veclen = node->simdclone->simdlen;
   if (POINTER_TYPE_P (t))
@@ -618,8 +621,12 @@ simd_clone_adjust_argument_types (struct cgraph_node *node)
 	    veclen = sc->vecsize_int;
 	  else
 	    veclen = sc->vecsize_float;
-	  veclen = exact_div (veclen,
-			      GET_MODE_BITSIZE (SCALAR_TYPE_MODE (parm_type)));
+	  if (known_eq (veclen, 0))
+	    veclen = sc->simdlen;
+	  else
+	    veclen
+	      = exact_div (veclen,
+			   GET_MODE_BITSIZE (SCALAR_TYPE_MODE (parm_type)));
 	  if (multiple_p (veclen, sc->simdlen))
 	    veclen = sc->simdlen;
 	  adj.op = IPA_PARAM_OP_NEW;
@@ -669,8 +676,11 @@ simd_clone_adjust_argument_types (struct cgraph_node *node)
 	veclen = sc->vecsize_int;
       else
 	veclen = sc->vecsize_float;
-      veclen = exact_div (veclen,
-			  GET_MODE_BITSIZE (SCALAR_TYPE_MODE (base_type)));
+      if (known_eq (veclen, 0))
+	veclen = sc->simdlen;
+      else
+	veclen = exact_div (veclen,
+			    GET_MODE_BITSIZE (SCALAR_TYPE_MODE (base_type)));
       if (multiple_p (veclen, sc->simdlen))
 	veclen = sc->simdlen;
       if (sc->mask_mode != VOIDmode)
diff --git a/gcc/target.def b/gcc/target.def
index 2a7fa68f83d..4d49ffc2c88 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -1629,6 +1629,9 @@ DEFHOOK
 "This hook should set @var{vecsize_mangle}, @var{vecsize_int}, @var{vecsize_float}\n\
 fields in @var{simd_clone} structure pointed by @var{clone_info} argument and also\n\
 @var{simdlen} field if it was previously 0.\n\
+@var{vecsize_mangle} is a marker for the backend only. @var{vecsize_int} and\n\
+@var{vecsize_float} should be left zero on targets where the number of lanes is\n\
+not determined by the bitsize (in which case @var{simdlen} is always used).\n\
 The hook should return 0 if SIMD clones shouldn't be emitted,\n\
 or number of @var{vecsize_mangle} variants that should be emitted.",
 int, (struct cgraph_node *, struct cgraph_simd_clone *, tree, int), NULL)