cmd/compile: inline closures with captures

When inlining a closure with captured variables, walk up the
param chain to find the one that is defined inside the scope
into which the function is being inlined, and map occurrences
of the captures to temporary inlvars, similarly to what is
done for function parameters.

No noticeable impact on compilation speed and binary size.

Minor improvements to go1 benchmarks on darwin/amd64

name                     old time/op    new time/op    delta
BinaryTree17-4              2.59s ± 3%     2.58s ± 1%    ~     (p=0.470 n=19+19)
Fannkuch11-4                3.15s ± 2%     3.15s ± 1%    ~     (p=0.647 n=20+19)
FmtFprintfEmpty-4          43.7ns ± 3%    43.4ns ± 4%    ~     (p=0.178 n=18+20)
FmtFprintfString-4         74.0ns ± 2%    77.1ns ± 7%  +4.13%  (p=0.000 n=20+20)
FmtFprintfInt-4            77.2ns ± 3%    79.2ns ± 6%  +2.53%  (p=0.000 n=20+20)
FmtFprintfIntInt-4          112ns ± 4%     112ns ± 2%    ~     (p=0.672 n=20+19)
FmtFprintfPrefixedInt-4     136ns ± 1%     135ns ± 2%    ~     (p=0.827 n=16+20)
FmtFprintfFloat-4           232ns ± 2%     233ns ± 1%    ~     (p=0.194 n=20+20)
FmtManyArgs-4               490ns ± 2%     484ns ± 2%  -1.28%  (p=0.001 n=20+20)
GobDecode-4                6.68ms ± 2%    6.72ms ± 2%    ~     (p=0.113 n=20+19)
GobEncode-4                5.62ms ± 2%    5.71ms ± 2%  +1.64%  (p=0.000 n=20+19)
Gzip-4                      235ms ± 3%     236ms ± 2%    ~     (p=0.607 n=20+19)
Gunzip-4                   37.1ms ± 2%    36.8ms ± 3%    ~     (p=0.060 n=20+20)
HTTPClientServer-4         61.9µs ± 2%    62.7µs ± 4%  +1.24%  (p=0.007 n=18+19)
JSONEncode-4               12.5ms ± 2%    12.4ms ± 3%    ~     (p=0.192 n=20+20)
JSONDecode-4               51.6ms ± 3%    51.0ms ± 3%  -1.19%  (p=0.008 n=20+19)
Mandelbrot200-4            4.12ms ± 6%    4.06ms ± 5%    ~     (p=0.063 n=20+20)
GoParse-4                  3.12ms ± 5%    3.10ms ± 2%    ~     (p=0.402 n=19+19)
RegexpMatchEasy0_32-4      80.7ns ± 2%    75.1ns ± 9%  -6.94%  (p=0.000 n=17+20)
RegexpMatchEasy0_1K-4       197ns ± 2%     186ns ± 2%  -5.43%  (p=0.000 n=20+20)
RegexpMatchEasy1_32-4      77.5ns ± 4%    71.9ns ± 7%  -7.25%  (p=0.000 n=20+18)
RegexpMatchEasy1_1K-4       341ns ± 3%     341ns ± 3%    ~     (p=0.732 n=20+20)
RegexpMatchMedium_32-4      113ns ± 2%     112ns ± 3%    ~     (p=0.102 n=20+20)
RegexpMatchMedium_1K-4     36.6µs ± 2%    35.8µs ± 2%  -2.26%  (p=0.000 n=18+20)
RegexpMatchHard_32-4       1.75µs ± 3%    1.74µs ± 2%    ~     (p=0.473 n=20+19)
RegexpMatchHard_1K-4       52.6µs ± 2%    52.0µs ± 3%  -1.15%  (p=0.005 n=20+20)
Revcomp-4                   381ms ± 4%     377ms ± 2%    ~     (p=0.067 n=20+18)
Template-4                 57.3ms ± 2%    57.7ms ± 2%    ~     (p=0.108 n=20+20)
TimeParse-4                 291ns ± 3%     292ns ± 2%    ~     (p=0.585 n=20+20)
TimeFormat-4                314ns ± 3%     315ns ± 1%    ~     (p=0.681 n=20+20)
[Geo mean]                 47.4µs         47.1µs       -0.73%

name                     old speed      new speed      delta
GobDecode-4               115MB/s ± 2%   114MB/s ± 2%    ~     (p=0.115 n=20+19)
GobEncode-4               137MB/s ± 2%   134MB/s ± 2%  -1.63%  (p=0.000 n=20+19)
Gzip-4                   82.5MB/s ± 3%  82.4MB/s ± 2%    ~     (p=0.612 n=20+19)
Gunzip-4                  523MB/s ± 2%   528MB/s ± 3%    ~     (p=0.060 n=20+20)
JSONEncode-4              155MB/s ± 2%   156MB/s ± 3%    ~     (p=0.192 n=20+20)
JSONDecode-4             37.6MB/s ± 3%  38.1MB/s ± 3%  +1.21%  (p=0.007 n=20+19)
GoParse-4                18.6MB/s ± 4%  18.7MB/s ± 2%    ~     (p=0.405 n=19+19)
RegexpMatchEasy0_32-4     396MB/s ± 2%   426MB/s ± 8%  +7.56%  (p=0.000 n=17+20)
RegexpMatchEasy0_1K-4    5.18GB/s ± 2%  5.48GB/s ± 2%  +5.79%  (p=0.000 n=20+20)
RegexpMatchEasy1_32-4     413MB/s ± 4%   444MB/s ± 6%  +7.46%  (p=0.000 n=20+19)
RegexpMatchEasy1_1K-4    3.00GB/s ± 3%  3.00GB/s ± 3%    ~     (p=0.678 n=20+20)
RegexpMatchMedium_32-4   8.82MB/s ± 2%  8.90MB/s ± 3%  +0.99%  (p=0.044 n=20+20)
RegexpMatchMedium_1K-4   28.0MB/s ± 2%  28.6MB/s ± 2%  +2.32%  (p=0.000 n=18+20)
RegexpMatchHard_32-4     18.3MB/s ± 3%  18.4MB/s ± 2%    ~     (p=0.482 n=20+19)
RegexpMatchHard_1K-4     19.5MB/s ± 2%  19.7MB/s ± 3%  +1.18%  (p=0.004 n=20+20)
Revcomp-4                 668MB/s ± 4%   674MB/s ± 2%    ~     (p=0.066 n=20+18)
Template-4               33.8MB/s ± 2%  33.6MB/s ± 2%    ~     (p=0.104 n=20+20)
[Geo mean]                124MB/s        126MB/s       +1.54%

Updates #15561
Updates #18270

Change-Id: I980086efe28b36aa27f81577065e2a729ff03d4e
Reviewed-on: https://go-review.googlesource.com/72490
Reviewed-by: Hugues Bruant <hugues.bruant@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 110 insertions, 0 deletions

diff --git a/test/closure3.dir/main.go b/test/closure3.dir/main.go
index 5629a522d7..4364343160 100644
--- a/test/closure3.dir/main.go
+++ b/test/closure3.dir/main.go
@@ -170,4 +170,114 @@ func main() {
 			}
 		}()
 	}
+
+	{
+		x := 42
+		if y := func() int { // ERROR "can inline main.func20"
+			return x
+		}(); y != 42 { // ERROR "inlining call to main.func20"
+			panic("y != 42")
+		}
+		if y := func() int { // ERROR "can inline main.func21" "func literal does not escape"
+			return x
+		}; y() != 42 { // ERROR "inlining call to main.func21"
+			panic("y() != 42")
+		}
+	}
+
+	{
+		x := 42
+		if z := func(y int) int { // ERROR "func literal does not escape"
+			return func() int { // ERROR "can inline main.func22.1"
+				return x + y
+			}() // ERROR "inlining call to main.func22.1"
+		}(1); z != 43 {
+			panic("z != 43")
+		}
+		if z := func(y int) int { // ERROR "func literal does not escape"
+			return func() int { // ERROR "can inline main.func23.1"
+				return x + y
+			}() // ERROR "inlining call to main.func23.1"
+		}; z(1) != 43 {
+			panic("z(1) != 43")
+		}
+	}
+
+	{
+		a := 1
+		func() { // ERROR "func literal does not escape"
+			func() { // ERROR "can inline main.func24"
+				a = 2
+			}() // ERROR "inlining call to main.func24" "&a does not escape"
+		}()
+		if a != 2 {
+			panic("a != 2")
+		}
+	}
+
+	{
+		b := 2
+		func(b int) { // ERROR "func literal does not escape"
+			func() { // ERROR "can inline main.func25.1"
+				b = 3
+			}() // ERROR "inlining call to main.func25.1" "&b does not escape"
+			if b != 3 {
+				panic("b != 3")
+			}
+		}(b)
+		if b != 2 {
+			panic("b != 2")
+		}
+	}
+
+	{
+		c := 3
+		func() { // ERROR "func literal does not escape"
+			c = 4
+			func() { // ERROR "func literal does not escape"
+				if c != 4 {
+					panic("c != 4")
+				}
+			}()
+		}()
+		if c != 4 {
+			panic("c != 4")
+		}
+	}
+
+	{
+		a := 2
+		if r := func(x int) int { // ERROR "func literal does not escape"
+			b := 3
+			return func(y int) int { // ERROR "func literal does not escape"
+				c := 5
+				return func(z int) int { // ERROR "can inline main.func27.1.1"
+					return a*x + b*y + c*z
+				}(10) // ERROR "inlining call to main.func27.1.1"
+			}(100)
+		}(1000); r != 2350 {
+			panic("r != 2350")
+		}
+	}
+
+	{
+		a := 2
+		if r := func(x int) int { // ERROR "func literal does not escape"
+			b := 3
+			return func(y int) int { // ERROR "func literal does not escape"
+				c := 5
+				func(z int) { // ERROR "can inline main.func28.1.1"
+					a = a * x
+					b = b * y
+					c = c * z
+				}(10) // ERROR "inlining call to main.func28.1.1" "&a does not escape" "&b does not escape" "&c does not escape"
+				return a + c
+			}(100) + b
+		}(1000); r != 2350 {
+			panic("r != 2350")
+		}
+		if a != 2000 {
+			panic("a != 2000")
+		}
+	}
 }