* src/bytecode.c (exec_byte_code):
The old hack for working around spurious -Wclobbered warnings from GCC
no longer suffices; disable the warning locally.
This also makes the code slightly smaller and faster.

GCC seems to have difficulty allocating important global interpreter
variables in registers; telling it which ones to use for 'top' and 'pc'
makes a big difference and seems to ease pressure enough for it to
deal with other variables as well.

We do it for AMD64 and ARM64.  Clang doesn't seem to need these directives.
It does result in -Wclobbered warnings that seem difficult to silence.

* src/bytecode.c (BC_REG_TOP, BC_REG_PC): New.
(exec_byte_code): Use them.

* src/bytecode.c (exec_byte_code):
Re-type op from int to ptrdiff_t, which avoids some useless conversions.
Reduce its use by using local variables for intra-block use,
and another variable (arg) where it doesn't need to be alive across
instruction dispatch.  We also eliminate it where performance doesn't
matter by re-fetching it from the instruction stream.

All this should help the register allocator.

Suggested by Arash Esbati <arash@gnu.org>.

When completion-ignore-case is non-nil, if all completions share
a common prefix ignoring case, try-completion has always
returned that.  Now, if all completions also share a common
prefix including case, try-completion includes that common
prefix in its return value (bug#79377).

* lisp/minibuffer.el (completion-pcm--merge-completions): Always
use return value from try-completion, which may change case.
* src/minibuf.c (Ftry_completion): Return the common prefix
which changes case.
* test/lisp/minibuffer-tests.el (completion-pcm-bug4219)
(completion-substring-test-5): New tests.

* lisp/vc/diff-mode.el (diff-refine-removed, diff-refine-added):
* lisp/vc/ediff-init.el (ediff-fine-diff-A, ediff-fine-diff-B):
* lisp/vc/smerge-mode.el (smerge-refined-removed, smerge-refined-added):
Lower the dominant component of RGB colors from "aa" to "88" (bug#79633).

(treesit-up-list): Better handle multi-language buffers.
(treesit-hs-find-next-block): Fix off-by-one error.

* lisp/vc/vc-hooks.el (vc-after-revert): New function.
(after-revert-hook): Add it.