Tweak compiler optimization evaluation section

* Remove references to the platform - this is unlikely to affect whether
copies are optimized.
* Note that the evaluation should test extreme optimisation settings.

Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/docs/architecture/psa-shared-memory.md b/docs/architecture/psa-shared-memory.md
index 7e2c280..a962839 100644
--- a/docs/architecture/psa-shared-memory.md
+++ b/docs/architecture/psa-shared-memory.md
@@ -238,12 +238,12 @@
 
 It is unclear whether the compiler will attempt to optimize away copying operations.
 
-Once the copying code is implemented, it should be evaluated to see whether compiler optimization is a problem. Specifically, for the major compilers and platforms supported by Mbed TLS:
+Once the copying code is implemented, it should be evaluated to see whether compiler optimization is a problem. Specifically, for the major compilers supported by Mbed TLS:
 * Write a small program that uses a PSA function which copies inputs or outputs.
-* Build the program with link-time optimization / full-program optimization enabled (e.g. `-flto` with `gcc`).
+* Build the program with link-time optimization / full-program optimization enabled (e.g. `-flto` with `gcc`). Try also enabling the most extreme optimization options such as `-Ofast` (`gcc`) and `-Oz` (`clang`).
 * Inspect the generated code with `objdump` or a similar tool to see if copying operations are preserved.
 
-If copying behaviour is preserved by all major compilers and platforms then assume that compiler optimization is not a problem.
+If copying behaviour is preserved by all major compilers then assume that compiler optimization is not a problem.
 
 If copying behaviour is optimized away by the compiler, further investigation is needed. Experiment with using the `volatile` keyword to force the compiler not to optimize accesses to the copied buffers.