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Rollup merge of #78873 - tmiasko:inline-opts, r=oli-obk

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Add flags customizing behaviour of MIR inlining

* `-Zinline-mir-threshold` to change the default threshold.
* `-Zinline-mir-hint-threshold` to change the threshold used by
  functions with inline hint.

Having those as configurable flags makes it possible to experiment with with
different inlining thresholds and substantially increase test coverage of MIR
inlining when used with increased thresholds (for example, necessary to test
#78844).
This commit is contained in:
Jonas Schievink 2020-11-11 20:59:03 +01:00 • committed by GitHub
commit 919177f7e4
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5 changed files with 86 additions and 4 deletions
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9
compiler/rustc_mir/src/transform/inline.rs
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@ -16,9 +16,6 @@ use crate::transform::MirPass;
use std::iter;
use std::ops::{Range, RangeFrom};
const DEFAULT_THRESHOLD: usize = 50;
const HINT_THRESHOLD: usize = 100;
const INSTR_COST: usize = 5;
const CALL_PENALTY: usize = 25;
const LANDINGPAD_PENALTY: usize = 50;
@ -248,7 +245,11 @@ impl Inliner<'tcx> {
}
}
let mut threshold = if hinted { HINT_THRESHOLD } else { DEFAULT_THRESHOLD };
let mut threshold = if hinted {
self.tcx.sess.opts.debugging_opts.inline_mir_hint_threshold
} else {
self.tcx.sess.opts.debugging_opts.inline_mir_threshold
};
// Significantly lower the threshold for inlining cold functions
if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::COLD) {