arm: Fix multilib mapping for CDE extensions [PR100856]

This is a followup to Srinath's recent patch: the newly added test is
failing e.g. on arm-linux-gnueabihf without R/M profile multilibs.

It is also failing on arm-eabi with R/M profile multilibs if the
execution engine does not support v8.1-M instructions.

The patch avoids this by adding check_effective_target_FUNC_multilib
in target-supports.exp which effectively checks whether the target
supports linking and execution, like what is already done for other
ARM effective targets.  pr100856.c is updated to use it instead of
arm_v8_1m_main_cde_mve_ok (which makes the testcase a bit of a
duplicate with check_effective_target_FUNC_multilib).

In addition, I noticed that requiring MVE does not seem necessary and
this enables the test to pass even when targeting a CPU without MVE:
since the test does not involve actual CDE instructions, it can pass
on other architecture versions.  For instance, when requiring MVE, we
have to use cortex-m55 under QEMU for the test to pass because the
memset() that comes from v8.1-m.main+mve multilib uses LOB
instructions (DLS) (memset is used during startup).  Keeping
arm_v8_1m_main_cde_mve_ok would mean we would enable the test provided
we have the right multilibs, causing a runtime error if the simulator
does not support LOB instructions (e.g. when targeting cortex-m7).

I do not update sourcebuild.texi since the CDE effective targets are
already collectively documented.

Finally, the patch fixes two typos in comments.

2021-07-15  Christophe Lyon  <christophe.lyon@foss.st.com>

	PR target/100856
	gcc/
	* config/arm/arm.opt: Fix typo.
	* config/arm/t-rmprofile: Fix typo.

	gcc/testsuite/
	* gcc.target/arm/acle/pr100856.c: Use arm_v8m_main_cde_multilib
	and arm_v8m_main_cde.
	* lib/target-supports.exp: Add
	check_effective_target_FUNC_multilib for ARM CDE.

gcc/config/arm/arm.opt

@@ -82,7 +82,7 @@ EnumValue
 Enum(arm_arch) String(native) Value(-1) DriverOnly
 
 ; Set to the name of target architecture which is required for
-; multilib linking.  This option is undocumented becuase it
+; multilib linking.  This option is undocumented because it
 ; should not be used by the users.
 mlibarch=
 Target RejectNegative JoinedOrMissing NoDWARFRecord DriverOnly Undocumented

gcc/config/arm/t-rmprofile

@@ -54,7 +54,7 @@ MULTILIB_REQUIRED	+= mthumb/march=armv8.1-m.main+mve/mfloat-abi=hard
 MULTILIB_MATCHES	+= march?armv6s-m=march?armv6-m
 
 # For all MULITIB_MATCHES for v8-m and above add mlibarch? on the right hand side
-# of = in the variant string instead of march?.  This is needed becuase all the
+# of = in the variant string instead of march?.  This is needed because all the
 # MULITIB_MATCHES variant strings are compared with mlibarch option for multilib
 # linking.
 

gcc/testsuite/gcc.target/arm/acle/pr100856.c

@@ -1,6 +1,6 @@
 /* { dg-do run } */
-/* { dg-require-effective-target arm_v8_1m_main_cde_mve_ok } */
-/* { dg-add-options arm_v8_1m_main_cde_mve } */
+/* { dg-require-effective-target arm_v8m_main_cde_multilib } */
+/* { dg-add-options arm_v8m_main_cde } */
 
 #include "arm_cde.h"
 

gcc/testsuite/lib/target-supports.exp

@@ -5518,6 +5518,24 @@ foreach { armfunc armflag armdef arminc } {
 	    global et_FUNC_flags
 	    return "$flags $et_FUNC_flags"
 	}
+
+	proc check_effective_target_FUNC_multilib { } {
+	    if { ! [check_effective_target_FUNC_ok] } {
+		return 0;
+	    }
+	    return [check_runtime FUNC_multilib {
+		#if !(DEF)
+		#error "DEF failed"
+		#endif
+		#include <arm_cde.h>
+		INC
+		int
+		main (void)
+		{
+		    return 0;
+		}
+	    } [add_options_for_FUNC ""]]
+        }
     }]
 }