Fix vect_float markup for a couple of tests (PR 83888)

vect_float is true for arm*-*-* targets, but the support is only
available when -funsafe-math-optimizations is on.  This caused
failures in two tests that disable fast-math.

The easiest fix seemed to be to add a new target selector for
"vect_float without special options".

2018-01-23  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR testsuite/83888
	* doc/sourcebuild.texi (vect_float): Say that the selector
	only describes the situation when -funsafe-math-optimizations is on.
	(vect_float_strict): Document.

gcc/testsuite/
	PR testsuite/83888
	* lib/target-supports.exp (check_effective_target_vect_float): Say
	that the result only holds when -funsafe-math-optimizations is on.
	(check_effective_target_vect_float_strict): New procedure.
	* gcc.dg/vect/no-fast-math-vect16.c: Use vect_float_strict instead
	of vect_float.
	* gcc.dg/vect/vect-reduc-6.c: Likewise.

From-SVN: r256977

gcc/ChangeLog

 2018-01-23  Richard Sandiford  <richard.sandiford@linaro.org>
 
+	PR testsuite/83888
+	* doc/sourcebuild.texi (vect_float): Say that the selector
+	only describes the situation when -funsafe-math-optimizations is on.
+	(vect_float_strict): Document.
+
+2018-01-23  Richard Sandiford  <richard.sandiford@linaro.org>
+
 	PR tree-optimization/83965
 	* tree-vect-patterns.c (vect_reassociating_reduction_p): New function.
 	(vect_recog_dot_prod_pattern, vect_recog_sad_pattern): Use it

gcc/doc/sourcebuild.texi

@@ -1403,7 +1403,13 @@ The target's preferred vector alignment is the same as the element
 alignment.
 
 @item vect_float
-Target supports hardware vectors of @code{float}.
+Target supports hardware vectors of @code{float} when
+@option{-funsafe-math-optimizations} is in effect.
+
+@item vect_float_strict
+Target supports hardware vectors of @code{float} when
+@option{-funsafe-math-optimizations} is not in effect.
+This implies @code{vect_float}.
 
 @item vect_int
 Target supports hardware vectors of @code{int}.

gcc/testsuite/ChangeLog

 2018-01-23  Richard Sandiford  <richard.sandiford@linaro.org>
 
+	PR testsuite/83888
+	* lib/target-supports.exp (check_effective_target_vect_float): Say
+	that the result only holds when -funsafe-math-optimizations is on.
+	(check_effective_target_vect_float_strict): New procedure.
+	* gcc.dg/vect/no-fast-math-vect16.c: Use vect_float_strict instead
+	of vect_float.
+	* gcc.dg/vect/vect-reduc-6.c: Likewise.
+
+2018-01-23  Richard Sandiford  <richard.sandiford@linaro.org>
+
 	PR tree-optimization/83965
 	* gcc.dg/vect/pr83965.c: New test.
 

gcc/testsuite/gcc.dg/vect/no-fast-math-vect16.c

-/* { dg-require-effective-target vect_float } */
+/* { dg-require-effective-target vect_float_strict } */
 
 #include <stdarg.h>
 #include "tree-vect.h"

gcc/testsuite/gcc.dg/vect/vect-reduc-6.c

-/* { dg-require-effective-target vect_float } */
+/* { dg-require-effective-target vect_float_strict } */
 /* { dg-additional-options "-fno-fast-math" } */
 
 #include <stdarg.h>

gcc/testsuite/lib/target-supports.exp

@@ -5492,7 +5492,8 @@ proc check_effective_target_vect_long { } {
     return $answer
 }
 
-# Return 1 if the target supports hardware vectors of float, 0 otherwise.
+# Return 1 if the target supports hardware vectors of float when
+# -funsafe-math-optimizations is enabled, 0 otherwise.
 #
 # This won't change for different subtargets so cache the result.
 
@@ -5525,6 +5526,14 @@ proc check_effective_target_vect_float { } {
     return $et_vect_float_saved($et_index)
 }
 
+# Return 1 if the target supports hardware vectors of float without
+# -funsafe-math-optimizations being enabled, 0 otherwise.
+
+proc check_effective_target_vect_float_strict { } {
+    return [expr { [check_effective_target_vect_float]
+		   && ![istarget arm*-*-*] }]
+}
+
 # Return 1 if the target supports hardware vectors of double, 0 otherwise.
 #
 # This won't change for different subtargets so cache the result.