cmd/compile: convert constants to interfaces without allocating

The order pass is responsible for ensuring that
values passed to runtime functions, including
convT2E/convT2I, are addressable.

Prior to this CL, this was always accomplished
by creating a temp, which frequently escaped to
the heap, causing allocations, perhaps most
notably in code like:

fmt.Println(1, 2, 3) // allocates three times

None of the runtime routines modify the contents
of the pointers they receive, so in the case of
constants, instead of creating a temp value,
we can create a static value.

(Marking the static value as read-only provides
protection against accidental attempts by the runtime
to modify the constant data.)

This improves code generation for code like:

panic("abc")
c <- 2 // c is a chan int

which can now simply refer to "abc" and 2,
rather than going by way of a temporary.

It also allows us to optimize convT2E/convT2I,
by recognizing static readonly values
and directly constructing the interface.

This CL adds ~0.5% to binary size, despite
decreasing the size of many functions,
because it also adds many static symbols.

This binary size regression could be recovered in
future (but currently unplanned) work.

There is a lot of content-duplication in these
symbols; this statement generates six new symbols,
three containing an int 1 and three containing
a pointer to the string "a":

fmt.Println(1, 1, 1, "a", "a", "a")

These symbols could be made content-addressable.

Furthermore, these symbols are small, so the
alignment and naming overhead is large.
As with the go.strings section, these symbols
could be hidden and have their alignment reduced.

The changes to test/live.go make it impossible
(at least with current optimization techniques)
to place the values being passed to the runtime
in static symbols, preserving autotmp creation.

Fixes #18704

Benchmarks from fmt and go-kit's logging package:

github.com/go-kit/kit/log

name                      old time/op    new time/op    delta
JSONLoggerSimple-8          1.91µs ± 2%    2.11µs ±22%     ~     (p=1.000 n=9+10)
JSONLoggerContextual-8      2.60µs ± 6%    2.43µs ± 2%   -6.29%  (p=0.000 n=9+10)
Discard-8                    101ns ± 2%      34ns ±14%  -66.33%  (p=0.000 n=10+9)
OneWith-8                    161ns ± 1%     102ns ±16%  -36.78%  (p=0.000 n=10+10)
TwoWith-8                    175ns ± 3%     106ns ± 7%  -39.36%  (p=0.000 n=10+9)
TenWith-8                    293ns ± 3%     227ns ±15%  -22.44%  (p=0.000 n=9+10)
LogfmtLoggerSimple-8         704ns ± 2%     608ns ± 2%  -13.65%  (p=0.000 n=10+9)
LogfmtLoggerContextual-8     962ns ± 1%     860ns ±17%  -10.57%  (p=0.003 n=9+10)
NopLoggerSimple-8            188ns ± 1%     120ns ± 1%  -36.39%  (p=0.000 n=9+10)
NopLoggerContextual-8        379ns ± 1%     243ns ± 0%  -35.77%  (p=0.000 n=9+10)
ValueBindingTimestamp-8      577ns ± 1%     499ns ± 1%  -13.51%  (p=0.000 n=10+10)
ValueBindingCaller-8         898ns ± 2%     844ns ± 2%   -6.00%  (p=0.000 n=10+10)

name                      old alloc/op   new alloc/op   delta
JSONLoggerSimple-8            904B ± 0%      872B ± 0%   -3.54%  (p=0.000 n=10+10)
JSONLoggerContextual-8      1.20kB ± 0%    1.14kB ± 0%   -5.33%  (p=0.000 n=10+10)
Discard-8                    64.0B ± 0%     32.0B ± 0%  -50.00%  (p=0.000 n=10+10)
OneWith-8                    96.0B ± 0%     64.0B ± 0%  -33.33%  (p=0.000 n=10+10)
TwoWith-8                     160B ± 0%      128B ± 0%  -20.00%  (p=0.000 n=10+10)
TenWith-8                     672B ± 0%      640B ± 0%   -4.76%  (p=0.000 n=10+10)
LogfmtLoggerSimple-8          128B ± 0%       96B ± 0%  -25.00%  (p=0.000 n=10+10)
LogfmtLoggerContextual-8      304B ± 0%      240B ± 0%  -21.05%  (p=0.000 n=10+10)
NopLoggerSimple-8             128B ± 0%       96B ± 0%  -25.00%  (p=0.000 n=10+10)
NopLoggerContextual-8         304B ± 0%      240B ± 0%  -21.05%  (p=0.000 n=10+10)
ValueBindingTimestamp-8       159B ± 0%      127B ± 0%  -20.13%  (p=0.000 n=10+10)
ValueBindingCaller-8          112B ± 0%       80B ± 0%  -28.57%  (p=0.000 n=10+10)

name                      old allocs/op  new allocs/op  delta
JSONLoggerSimple-8            19.0 ± 0%      17.0 ± 0%  -10.53%  (p=0.000 n=10+10)
JSONLoggerContextual-8        25.0 ± 0%      21.0 ± 0%  -16.00%  (p=0.000 n=10+10)
Discard-8                     3.00 ± 0%      1.00 ± 0%  -66.67%  (p=0.000 n=10+10)
OneWith-8                     3.00 ± 0%      1.00 ± 0%  -66.67%  (p=0.000 n=10+10)
TwoWith-8                     3.00 ± 0%      1.00 ± 0%  -66.67%  (p=0.000 n=10+10)
TenWith-8                     3.00 ± 0%      1.00 ± 0%  -66.67%  (p=0.000 n=10+10)
LogfmtLoggerSimple-8          4.00 ± 0%      2.00 ± 0%  -50.00%  (p=0.000 n=10+10)
LogfmtLoggerContextual-8      7.00 ± 0%      3.00 ± 0%  -57.14%  (p=0.000 n=10+10)
NopLoggerSimple-8             4.00 ± 0%      2.00 ± 0%  -50.00%  (p=0.000 n=10+10)
NopLoggerContextual-8         7.00 ± 0%      3.00 ± 0%  -57.14%  (p=0.000 n=10+10)
ValueBindingTimestamp-8       5.00 ± 0%      3.00 ± 0%  -40.00%  (p=0.000 n=10+10)
ValueBindingCaller-8          4.00 ± 0%      2.00 ± 0%  -50.00%  (p=0.000 n=10+10)

fmt

name                             old time/op    new time/op    delta
SprintfPadding-8                   88.9ns ± 3%    79.1ns ± 1%   -11.09%  (p=0.000 n=10+7)
SprintfEmpty-8                     12.6ns ± 3%    12.8ns ± 3%      ~     (p=0.136 n=10+10)
SprintfString-8                    38.7ns ± 5%    26.9ns ± 6%   -30.65%  (p=0.000 n=10+10)
SprintfTruncateString-8            56.7ns ± 2%    47.0ns ± 3%   -17.05%  (p=0.000 n=10+10)
SprintfQuoteString-8                164ns ± 2%     153ns ± 2%    -7.01%  (p=0.000 n=10+10)
SprintfInt-8                       38.9ns ±15%    26.5ns ± 2%   -31.93%  (p=0.000 n=10+9)
SprintfIntInt-8                    60.3ns ± 9%    38.2ns ± 1%   -36.67%  (p=0.000 n=10+8)
SprintfPrefixedInt-8               58.6ns ±13%    51.2ns ±11%   -12.66%  (p=0.001 n=10+10)
SprintfFloat-8                     71.4ns ± 3%    64.2ns ± 3%   -10.08%  (p=0.000 n=8+10)
SprintfComplex-8                    175ns ± 3%     159ns ± 2%    -9.03%  (p=0.000 n=10+10)
SprintfBoolean-8                   33.5ns ± 4%    25.7ns ± 5%   -23.28%  (p=0.000 n=10+10)
SprintfHexString-8                 65.3ns ± 3%    51.7ns ± 5%   -20.86%  (p=0.000 n=10+9)
SprintfHexBytes-8                  67.2ns ± 5%    67.9ns ± 4%      ~     (p=0.383 n=10+10)
SprintfBytes-8                      129ns ± 7%     124ns ± 7%      ~     (p=0.074 n=9+10)
SprintfStringer-8                   127ns ± 4%     126ns ± 8%      ~     (p=0.506 n=9+10)
SprintfStructure-8                  357ns ± 3%     359ns ± 3%      ~     (p=0.469 n=10+10)
ManyArgs-8                          203ns ± 6%     126ns ± 3%   -37.94%  (p=0.000 n=10+10)
FprintInt-8                         119ns ±10%      74ns ± 3%   -37.54%  (p=0.000 n=10+10)
FprintfBytes-8                      122ns ± 4%     120ns ± 3%      ~     (p=0.124 n=10+10)
FprintIntNoAlloc-8                 78.2ns ± 5%    74.1ns ± 3%    -5.28%  (p=0.000 n=10+10)
ScanInts-8                          349µs ± 1%     349µs ± 0%      ~     (p=0.606 n=9+8)
ScanRecursiveInt-8                 43.8ms ± 7%    40.1ms ± 2%    -8.42%  (p=0.000 n=10+10)
ScanRecursiveIntReaderWrapper-8    43.5ms ± 4%    40.4ms ± 2%    -7.16%  (p=0.000 n=10+9)

name                             old alloc/op   new alloc/op   delta
SprintfPadding-8                    24.0B ± 0%     16.0B ± 0%   -33.33%  (p=0.000 n=10+10)
SprintfEmpty-8                      0.00B          0.00B           ~     (all equal)
SprintfString-8                     21.0B ± 0%      5.0B ± 0%   -76.19%  (p=0.000 n=10+10)
SprintfTruncateString-8             32.0B ± 0%     16.0B ± 0%   -50.00%  (p=0.000 n=10+10)
SprintfQuoteString-8                48.0B ± 0%     32.0B ± 0%   -33.33%  (p=0.000 n=10+10)
SprintfInt-8                        16.0B ± 0%      1.0B ± 0%   -93.75%  (p=0.000 n=10+10)
SprintfIntInt-8                     24.0B ± 0%      3.0B ± 0%   -87.50%  (p=0.000 n=10+10)
SprintfPrefixedInt-8                72.0B ± 0%     64.0B ± 0%   -11.11%  (p=0.000 n=10+10)
SprintfFloat-8                      16.0B ± 0%      8.0B ± 0%   -50.00%  (p=0.000 n=10+10)
SprintfComplex-8                    48.0B ± 0%     32.0B ± 0%   -33.33%  (p=0.000 n=10+10)
SprintfBoolean-8                    8.00B ± 0%     4.00B ± 0%   -50.00%  (p=0.000 n=10+10)
SprintfHexString-8                  96.0B ± 0%     80.0B ± 0%   -16.67%  (p=0.000 n=10+10)
SprintfHexBytes-8                    112B ± 0%      112B ± 0%      ~     (all equal)
SprintfBytes-8                      96.0B ± 0%     96.0B ± 0%      ~     (all equal)
SprintfStringer-8                   32.0B ± 0%     32.0B ± 0%      ~     (all equal)
SprintfStructure-8                   256B ± 0%      256B ± 0%      ~     (all equal)
ManyArgs-8                          80.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
FprintInt-8                         8.00B ± 0%     0.00B       -100.00%  (p=0.000 n=10+10)
FprintfBytes-8                      32.0B ± 0%     32.0B ± 0%      ~     (all equal)
FprintIntNoAlloc-8                  0.00B          0.00B           ~     (all equal)
ScanInts-8                         15.2kB ± 0%    15.2kB ± 0%      ~     (p=0.248 n=9+10)
ScanRecursiveInt-8                 21.6kB ± 0%    21.6kB ± 0%      ~     (all equal)
ScanRecursiveIntReaderWrapper-8    21.7kB ± 0%    21.7kB ± 0%      ~     (all equal)

name                             old allocs/op  new allocs/op  delta
SprintfPadding-8                     2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)
SprintfEmpty-8                       0.00           0.00           ~     (all equal)
SprintfString-8                      2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)
SprintfTruncateString-8              2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)
SprintfQuoteString-8                 2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)
SprintfInt-8                         2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)
SprintfIntInt-8                      3.00 ± 0%      1.00 ± 0%   -66.67%  (p=0.000 n=10+10)
SprintfPrefixedInt-8                 2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)
SprintfFloat-8                       2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)
SprintfComplex-8                     2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)
SprintfBoolean-8                     2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)
SprintfHexString-8                   2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)
SprintfHexBytes-8                    2.00 ± 0%      2.00 ± 0%      ~     (all equal)
SprintfBytes-8                       2.00 ± 0%      2.00 ± 0%      ~     (all equal)
SprintfStringer-8                    4.00 ± 0%      4.00 ± 0%      ~     (all equal)
SprintfStructure-8                   7.00 ± 0%      7.00 ± 0%      ~     (all equal)
ManyArgs-8                           8.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)
FprintInt-8                          1.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)
FprintfBytes-8                       1.00 ± 0%      1.00 ± 0%      ~     (all equal)
FprintIntNoAlloc-8                   0.00           0.00           ~     (all equal)
ScanInts-8                          1.60k ± 0%     1.60k ± 0%      ~     (all equal)
ScanRecursiveInt-8                  1.71k ± 0%     1.71k ± 0%      ~     (all equal)
ScanRecursiveIntReaderWrapper-8     1.71k ± 0%     1.71k ± 0%      ~     (all equal)

Change-Id: I7ba72a25fea4140a0ba40a9f443103ed87cc69b5
Reviewed-on: https://go-review.googlesource.com/35554
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

1 files changed, 27 insertions, 21 deletions

diff --git a/test/live.go b/test/live.go
index b23e1509e0..462f3ef12e 100644
--- a/test/live.go
+++ b/test/live.go
@@ -141,7 +141,7 @@ var i9 interface{}
 func f9() bool {
 	g8()
 	x := i9
-	y := interface{}(99.0i) // ERROR "live at call to convT2E: x.data x.type$"
+	y := interface{}(str()) // ERROR "live at call to convT2E: .autotmp_[0-9]+ x.data x.type$" "live at call to str: x.data x.type$"
 	i9 = y                  // make y escape so the line above has to call convT2E
 	return x != y
 }
@@ -256,12 +256,15 @@ func g15() string
 
 var m map[string]int
 
+// str is used to ensure that a temp is required for runtime calls below.
+func str() string
+
 func f16() {
 	if b {
-		delete(m, "hi") // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
+		delete(m, str()) // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
 	}
-	delete(m, "hi") // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
-	delete(m, "hi") // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
+	delete(m, str()) // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
+	delete(m, str()) // ERROR "live at call to mapdelete: .autotmp_[0-9]+$"
 }
 
 var m2s map[string]*byte
@@ -280,19 +283,19 @@ func f17a(p *byte) { // ERROR "live at entry to f17a: p$"
 func f17b(p *byte) { // ERROR "live at entry to f17b: p$"
 	// key temporary
 	if b {
-		m2s["x"] = p // ERROR "live at call to mapassign: p .autotmp_[0-9]+$"
+		m2s[str()] = p // ERROR "live at call to mapassign: p .autotmp_[0-9]+$" "live at call to str: p$"
 	}
-	m2s["x"] = p // ERROR "live at call to mapassign: p .autotmp_[0-9]+$"
-	m2s["x"] = p // ERROR "live at call to mapassign: p .autotmp_[0-9]+$"
+	m2s[str()] = p // ERROR "live at call to mapassign: p .autotmp_[0-9]+$" "live at call to str: p$"
+	m2s[str()] = p // ERROR "live at call to mapassign: p .autotmp_[0-9]+$" "live at call to str: p$"
 }
 
 func f17c() {
 	// key and value temporaries
 	if b {
-		m2s["x"] = f17d() // ERROR "live at call to f17d: .autotmp_[0-9]+$" "live at call to mapassign: .autotmp_[0-9]+ .autotmp_[0-9]+$"
+		m2s[str()] = f17d() // ERROR "live at call to f17d: .autotmp_[0-9]+$" "live at call to mapassign: .autotmp_[0-9]+ .autotmp_[0-9]+$"
 	}
-	m2s["x"] = f17d() // ERROR "live at call to f17d: .autotmp_[0-9]+$" "live at call to mapassign: .autotmp_[0-9]+ .autotmp_[0-9]+$"
-	m2s["x"] = f17d() // ERROR "live at call to f17d: .autotmp_[0-9]+$" "live at call to mapassign: .autotmp_[0-9]+ .autotmp_[0-9]+$"
+	m2s[str()] = f17d() // ERROR "live at call to f17d: .autotmp_[0-9]+$" "live at call to mapassign: .autotmp_[0-9]+ .autotmp_[0-9]+$"
+	m2s[str()] = f17d() // ERROR "live at call to f17d: .autotmp_[0-9]+$" "live at call to mapassign: .autotmp_[0-9]+ .autotmp_[0-9]+$"
 }
 
 func f17d() *byte
@@ -313,6 +316,9 @@ func f18() {
 
 var ch chan *byte
 
+// byteptr is used to ensure that a temp is required for runtime calls below.
+func byteptr() *byte
+
 func f19() {
 	// dest temporary for channel receive.
 	var z *byte
@@ -328,10 +334,10 @@ func f19() {
 func f20() {
 	// src temporary for channel send
 	if b {
-		ch <- nil // ERROR "live at call to chansend1: .autotmp_[0-9]+$"
+		ch <- byteptr() // ERROR "live at call to chansend1: .autotmp_[0-9]+$"
 	}
-	ch <- nil // ERROR "live at call to chansend1: .autotmp_[0-9]+$"
-	ch <- nil // ERROR "live at call to chansend1: .autotmp_[0-9]+$"
+	ch <- byteptr() // ERROR "live at call to chansend1: .autotmp_[0-9]+$"
+	ch <- byteptr() // ERROR "live at call to chansend1: .autotmp_[0-9]+$"
 }
 
 func f21() {
@@ -488,13 +494,13 @@ func f30(b bool) {
 
 func f31(b1, b2, b3 bool) {
 	if b1 {
-		g31("a") // ERROR "live at call to convT2E: .autotmp_[0-9]+$" "live at call to g31: .autotmp_[0-9]+$"
+		g31(str()) // ERROR "live at call to convT2E: .autotmp_[0-9]+$" "live at call to g31: .autotmp_[0-9]+$"
 	}
 	if b2 {
-		h31("b") // ERROR "live at call to convT2E: .autotmp_[0-9]+ .autotmp_[0-9]+$" "live at call to h31: .autotmp_[0-9]+$" "live at call to newobject: .autotmp_[0-9]+$"
+		h31(str()) // ERROR "live at call to convT2E: .autotmp_[0-9]+ .autotmp_[0-9]+$" "live at call to h31: .autotmp_[0-9]+$" "live at call to newobject: .autotmp_[0-9]+$"
 	}
 	if b3 {
-		panic("asdf") // ERROR "live at call to convT2E: .autotmp_[0-9]+$" "live at call to gopanic: .autotmp_[0-9]+$"
+		panic(str()) // ERROR "live at call to convT2E: .autotmp_[0-9]+$" "live at call to gopanic: .autotmp_[0-9]+$"
 	}
 	print(b3)
 }
@@ -529,7 +535,7 @@ func call32(func())
 var m33 map[interface{}]int
 
 func f33() {
-	if m33[nil] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
+	if m33[byteptr()] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
 		printnl()
 		return
 	} else {
@@ -539,7 +545,7 @@ func f33() {
 }
 
 func f34() {
-	if m33[nil] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
+	if m33[byteptr()] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
 		printnl()
 		return
 	}
@@ -547,7 +553,7 @@ func f34() {
 }
 
 func f35() {
-	if m33[nil] == 0 && m33[nil] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
+	if m33[byteptr()] == 0 && m33[byteptr()] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
 		printnl()
 		return
 	}
@@ -555,7 +561,7 @@ func f35() {
 }
 
 func f36() {
-	if m33[nil] == 0 || m33[nil] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
+	if m33[byteptr()] == 0 || m33[byteptr()] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
 		printnl()
 		return
 	}
@@ -563,7 +569,7 @@ func f36() {
 }
 
 func f37() {
-	if (m33[nil] == 0 || m33[nil] == 0) && m33[nil] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
+	if (m33[byteptr()] == 0 || m33[byteptr()] == 0) && m33[byteptr()] == 0 { // ERROR "live at call to mapaccess1: .autotmp_[0-9]+$"
 		printnl()
 		return
 	}