Re: The Emacs master is much slower than the emacs-27 branch.

[Gregory Heytings]

> It occurred to me that the differences in the relative performance could 
> be due to a different GCC version and/

GCC is not the problem here, I just ran the same benchmark with Emacs 27 
compiled with different versions of GCC:

    | GCC 8.4 | GCC 9.3 | GCC 10.2 |
-Og |    ~67s |    ~68s |     ~67s |
-O0 |    ~63s |    ~63s |     ~63s |
-O1 |    ~26s |    ~27s |     ~26s |
-O2 |    ~18s |    ~18s |     ~18s |
-O3 |    ~18s |    ~17s |     ~17s |

> or the effect of inlining on 32-bit code vs 64-bit code produced by GCC.

That's possible indeed.