Doing nothing vs going pragma(inline, true) vs function literals

[p0nce]

ldc-developers/ldc#4388 (comment)

Need to makes a well balanced decision for this! Surprising development.

Problem statement:

• currently we'll have no inlining unless dub --combined is used, which is a major problem and not a LDC problem (EDIT: possibly not true anymore?)
• some LDC construct such as __ir builds slow currently, which is a minor problem, unresolved but not really important
• ideally we want intrinsics inlined or not, based upon the compiler deciding. Or we could live with a forced inlining for everything, which would itself be a minor issue.
• it's unclear how DMD will manage that amount of pragma(inline), apparently in top-level this should be relatively harmless since .di generation needs that. Historically, pragma(inline) inside body used to cause problems.
• reggae and redub builds needs pragma(inline, true) to build fast, as seen during redub development
• kinke expects our "intrinsics" to be of course pragma(inline, true) so I'm missing something
  • but that also inlines the body everywhere, as mentionned above
• function literals have differing linkage properties, as per-kinke response in ldc issues (read that) and could be used instead... maybe

[p0nce]

A redub build is 40% slower due to no --combined existing, is it an issue?