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Keith Randall ee59c06acb cmd/compile: evaluate map initializers incrementally
For the code:

m := map[int]int {
  a(): b(),
  c(): d(),
  e(): f(),
}

We used to do:

t1 := a()
t2 := b()
t3 := c()
t4 := d()
t5 := e()
t6 := f()
m := map[int]int{}
m[t1] = t2
m[t3] = t4
m[t5] = t6

After this CL we do:

m := map[int]int{}
t1 := a()
t2 := b()
m[t1] = t2
t3 := c()
t4 := d()
m[t3] = t4
t5 := e()
t6 := f()
m[t5] = t6

Ordering the initialization this way limits the lifetime of the
temporaries involved.  In particular, for large maps the number of
simultaneously live temporaries goes from ~2*len(m) to ~2. This change
makes the compiler (regalloc, mostly) a lot happier. The compiler runs
faster and uses a lot less memory.

For #26546, changes compile time of a big map from 8 sec to 0.5 sec.

Fixes #26552

Update #26546

Change-Id: Ib7d202dead3feaf493a464779fd9611c63fcc25f
Reviewed-on: https://go-review.googlesource.com/c/go/+/174417
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
2019-04-29 23:45:15 +00:00
.github .github: don't render author-facing text in ISSUE_TEMPLATE 2018-11-02 04:47:34 +00:00
api api: add recent Go 1.13 work 2019-04-26 05:16:33 +00:00
doc runtime: support all as parameter in gdb goroutine commands. 2019-04-29 18:11:11 +00:00
lib/time time: read 64-bit data if available 2019-02-26 23:10:35 +00:00
misc misc/wasm: fix command line arguments containing multi-byte characters 2019-04-29 17:33:47 +00:00
src cmd/compile: evaluate map initializers incrementally 2019-04-29 23:45:15 +00:00
test testing: delay flag registration; move to an Init function 2019-04-29 19:54:30 +00:00
.gitattributes
.gitignore .gitignore: ignore src/cmd/dist/dist 2017-10-28 21:55:49 +00:00
AUTHORS A: Add Maya Rashish (individual CLA) 2019-04-23 14:40:30 +00:00
CONTRIBUTING.md all: restore changes from faulty merge/revert 2018-02-12 20:13:59 +00:00
CONTRIBUTORS CONTRIBUTORS: second round of updates for Go 1.12 2019-01-30 18:01:19 +00:00
LICENSE doc: revert copyright date to 2009 2016-06-01 22:40:04 +00:00
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README.md README: linkify some paths 2018-06-06 18:07:01 +00:00
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The Go Programming Language

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