NCG: fast compilation of very large strings (#16190)

This patch adds an optimization into the NCG: for large strings
(threshold configurable via -fbinary-blob-threshold=NNN flag), instead
of printing `.asciz "..."` in the generated ASM source, we print
`.incbin "tmpXXX.dat"` and we dump the contents of the string into a
temporary "tmpXXX.dat" file.

See the note for more details.

1 files changed, 16 insertions, 0 deletions

diff --git a/docs/users_guide/using-optimisation.rst b/docs/users_guide/using-optimisation.rst
index cacc55325e..d6240bc5cb 100644
--- a/docs/users_guide/using-optimisation.rst
+++ b/docs/users_guide/using-optimisation.rst
@@ -1238,3 +1238,19 @@ by saying ``-fno-wombat``.
     if a function definition will be inlined *at a call site*. The other option
     determines if a function definition will be kept around at all for
     potential inlining.
+
+.. ghc-flag:: -fbinary-blob-threshold=⟨n⟩
+    :shortdesc: *default: 500K.* Tweak assembly generator for binary blobs.
+    :type: dynamic
+    :category: optimization
+
+    :default: 500000
+
+    The native code-generator can either dump binary blobs (e.g. string
+    literals) into the assembly file (by using ".asciz" or ".string" assembler
+    directives) or it can dump them as binary data into a temporary file which
+    is then included by the assembler (using the ".incbin" assembler directive).
+
+    This flag sets the size (in bytes) threshold above which the second approach
+    is used. You can disable the second approach entirely by setting the
+    threshold to 0.