Cherry pick 907a367b5035ab120095c325b48fdf90b04a5081 : Remove explicit width suffixes from Arm bignum assembly

[lhuang04]

Within the M-profile of the Arm architecture, some instructions admit both a 16-bit and a 32-bit encoding. For those instructions, some assemblers support the use of the .n (narrow) and .w (wide) suffixes to force a choice of instruction encoding width. Forcing the size of encodings may be useful to ensure alignment of code, which can have a significant performance impact on some microarchitectures.

It is for this reason that a previous commit introduced explicit .w suffixes into what was believed to be M-profile only assembly in library/bn_mul.h.

This change, however, introduced two issues:

• First, the assembly block in question is used also for Armv7-A systems, on which the .n/.w distinction is not meaningful (all instructions are 32-bit).
• Second, compiler support for .n/.w suffixes appears patchy, leading to compilation failures even when building for M-profile targets.

This commit removes the .w annotations in order to restore working code, deferring controlled re-introduction for the sake of performance.

Fixes #6089.

Signed-off-by: Hanno Becker [email protected]

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