mirror of
https://github.com/golang/go
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cmd/internal/obj/x86: make function prologue more predictable
Static branch prediction guesses that forward branches aren't taken.
Since stacks are rarely grown, make the forward branch mean grow.
Sample disassembly for
func f() {
_ = [128]byte{}
}
Before:
TEXT main.f(SB) x.go
x.go:3 0x2000 65488b0c25a0080000 GS MOVQ GS:0x8a0, CX
x.go:3 0x2009 483b6110 CMPQ 0x10(CX), SP
x.go:3 0x200d 7707 JA 0x2016
x.go:3 0x200f e88c410400 CALL runtime.morestack_noctxt(SB)
x.go:3 0x2014 ebea JMP main.f(SB)
x.go:3 0x2016 4881ec80000000 SUBQ $0x80, SP
x.go:4 0x201d 488d3c24 LEAQ 0(SP), DI
x.go:4 0x2021 31c0 XORL AX, AX
x.go:4 0x2023 e8cc640400 CALL 0x484f4
x.go:5 0x2028 4881c480000000 ADDQ $0x80, SP
x.go:5 0x202f c3 RET
After:
TEXT main.f(SB) x.go
x.go:3 0x2000 65488b0c25a0080000 GS MOVQ GS:0x8a0, CX
x.go:3 0x2009 483b6110 CMPQ 0x10(CX), SP
x.go:3 0x200d 761a JBE 0x2029
x.go:3 0x200f 4881ec80000000 SUBQ $0x80, SP
x.go:4 0x2016 488d3c24 LEAQ 0(SP), DI
x.go:4 0x201a 31c0 XORL AX, AX
x.go:4 0x201c e813740400 CALL 0x49434
x.go:5 0x2021 4881c480000000 ADDQ $0x80, SP
x.go:5 0x2028 c3 RET
x.go:3 0x2029 e8224f0400 CALL runtime.morestack_noctxt(SB)
x.go:3 0x202e ebd0 JMP main.f(SB)
Updates #10587.
Sample benchmarks on a 2.8 GHz Intel Core i7:
package sort
name old mean new mean delta
SearchWrappers 134ns × (0.99,1.01) 132ns × (0.99,1.01) -1.73% (p=0.000 n=15+14)
SortString1K 215µs × (0.99,1.01) 213µs × (0.99,1.01) -0.61% (p=0.020 n=14+15)
StableString1K 311µs × (0.99,1.02) 309µs × (0.99,1.02) ~ (p=0.077 n=14+15)
SortInt1K 103µs × (0.99,1.02) 100µs × (0.98,1.01) -3.34% (p=0.000 n=15+15)
StableInt1K 102µs × (0.99,1.01) 98µs × (0.97,1.04) -3.53% (p=0.000 n=15+15)
SortInt64K 10.1ms × (0.98,1.02) 9.7ms × (0.99,1.01) -3.86% (p=0.000 n=14+15)
StableInt64K 8.70ms × (0.99,1.01) 8.44ms × (0.99,1.03) -2.93% (p=0.000 n=14+15)
Sort1e2 51.2µs × (1.00,1.01) 48.9µs × (0.99,1.02) -4.48% (p=0.000 n=13+15)
Stable1e2 100µs × (0.99,1.02) 99µs × (0.99,1.01) -1.15% (p=0.000 n=14+13)
Sort1e4 11.1ms × (0.99,1.02) 10.4ms × (0.99,1.01) -6.02% (p=0.000 n=15+14)
Stable1e4 30.6ms × (0.99,1.01) 30.3ms × (0.99,1.02) -1.02% (p=0.001 n=15+14)
Sort1e6 1.75s × (0.99,1.02) 1.66s × (0.98,1.03) -4.95% (p=0.000 n=14+15)
Stable1e6 6.31s × (0.99,1.01) 6.26s × (0.99,1.01) -0.79% (p=0.002 n=15+15)
package regexp
name old mean new mean delta
Literal 131ns × (0.99,1.01) 130ns × (0.99,1.03) -1.07% (p=0.004 n=14+15)
NotLiteral 2.13µs × (0.99,1.01) 2.01µs × (0.99,1.03) -5.71% (p=0.000 n=14+14)
MatchClass 3.15µs × (0.99,1.01) 3.04µs × (0.99,1.02) -3.40% (p=0.000 n=15+15)
MatchClass_InRange 2.92µs × (0.99,1.01) 2.77µs × (0.99,1.02) -5.05% (p=0.000 n=13+15)
ReplaceAll 2.17µs × (0.99,1.02) 2.06µs × (0.99,1.01) -5.19% (p=0.000 n=15+13)
AnchoredLiteralShortNonMatch 116ns × (0.99,1.02) 113ns × (0.99,1.01) -2.75% (p=0.000 n=15+14)
AnchoredLiteralLongNonMatch 125ns × (0.99,1.01) 127ns × (0.98,1.02) +1.49% (p=0.000 n=15+15)
AnchoredShortMatch 178ns × (0.99,1.02) 175ns × (0.99,1.01) -1.62% (p=0.000 n=15+13)
AnchoredLongMatch 328ns × (0.99,1.00) 341ns × (0.99,1.01) +3.73% (p=0.000 n=12+15)
OnePassShortA 773ns × (0.99,1.02) 752ns × (0.99,1.01) -2.78% (p=0.000 n=15+13)
NotOnePassShortA 794ns × (0.99,1.03) 780ns × (0.99,1.02) -1.75% (p=0.001 n=15+15)
OnePassShortB 608ns × (0.99,1.01) 591ns × (0.99,1.02) -2.86% (p=0.000 n=15+14)
NotOnePassShortB 576ns × (0.99,1.01) 571ns × (0.99,1.02) -0.74% (p=0.035 n=15+15)
OnePassLongPrefix 131ns × (0.99,1.02) 130ns × (0.99,1.02) -1.32% (p=0.003 n=15+15)
OnePassLongNotPrefix 503ns × (0.99,1.02) 481ns × (0.99,1.01) -4.34% (p=0.000 n=15+13)
MatchEasy0_32 102ns × (0.98,1.01) 101ns × (0.99,1.02) ~ (p=0.907 n=15+14)
MatchEasy0_1K 617ns × (0.99,1.02) 634ns × (0.98,1.02) +2.77% (p=0.000 n=15+15)
MatchEasy0_32K 10.9µs × (0.99,1.01) 11.1µs × (0.99,1.01) +1.59% (p=0.000 n=15+15)
MatchEasy0_1M 406µs × (0.99,1.02) 410µs × (0.99,1.02) +1.01% (p=0.000 n=14+15)
MatchEasy0_32M 13.4ms × (0.99,1.01) 13.7ms × (0.99,1.02) +1.64% (p=0.000 n=12+15)
MatchEasy1_32 83.7ns × (0.98,1.02) 83.0ns × (0.98,1.02) ~ (p=0.190 n=15+15)
MatchEasy1_1K 1.46µs × (0.99,1.02) 1.39µs × (0.99,1.02) -4.83% (p=0.000 n=15+15)
MatchEasy1_32K 49.4µs × (0.99,1.01) 49.4µs × (0.99,1.01) ~ (p=0.205 n=15+15)
MatchEasy1_1M 1.72ms × (0.99,1.02) 1.75ms × (0.99,1.01) +1.34% (p=0.000 n=15+15)
MatchEasy1_32M 55.5ms × (0.99,1.01) 56.1ms × (0.99,1.02) +1.10% (p=0.002 n=15+15)
MatchMedium_32 1.37µs × (0.99,1.04) 1.33µs × (0.99,1.01) -2.87% (p=0.000 n=15+15)
MatchMedium_1K 41.1µs × (0.99,1.02) 40.4µs × (0.99,1.02) -1.59% (p=0.000 n=15+15)
MatchMedium_32K 1.71ms × (0.99,1.01) 1.75ms × (0.99,1.02) +2.36% (p=0.000 n=14+15)
MatchMedium_1M 54.5ms × (0.99,1.01) 56.1ms × (0.99,1.01) +2.94% (p=0.000 n=13+15)
MatchMedium_32M 1.75s × (0.99,1.01) 1.80s × (0.99,1.01) +2.77% (p=0.000 n=15+15)
MatchHard_32 2.12µs × (0.99,1.02) 2.06µs × (0.99,1.01) -2.60% (p=0.000 n=15+14)
MatchHard_1K 64.4µs × (0.98,1.02) 62.2µs × (0.99,1.01) -3.33% (p=0.000 n=15+15)
MatchHard_32K 2.74ms × (0.99,1.01) 2.75ms × (0.99,1.01) ~ (p=0.310 n=15+14)
MatchHard_1M 87.1ms × (0.99,1.02) 88.2ms × (0.99,1.01) +1.36% (p=0.000 n=14+15)
MatchHard_32M 2.79s × (0.99,1.02) 2.83s × (0.99,1.02) +1.26% (p=0.004 n=15+14)
go1 benchmarks
name old time/op new time/op delta
BinaryTree17 3.34s ± 3% 3.28s ± 2% -1.86% (p=0.000 n=67+66)
Fannkuch11 2.50s ± 1% 2.51s ± 1% +0.24% (p=0.016 n=63+66)
FmtFprintfEmpty 50.3ns ± 1% 50.2ns ± 2% -0.30% (p=0.001 n=62+67)
FmtFprintfString 178ns ± 1% 166ns ± 1% -7.10% (p=0.000 n=62+59)
FmtFprintfInt 168ns ± 1% 161ns ± 2% -4.41% (p=0.000 n=66+64)
FmtFprintfIntInt 292ns ± 1% 282ns ± 2% -3.55% (p=0.000 n=62+60)
FmtFprintfPrefixedInt 245ns ± 2% 239ns ± 2% -2.24% (p=0.000 n=66+65)
FmtFprintfFloat 338ns ± 2% 326ns ± 1% -3.42% (p=0.000 n=64+59)
FmtManyArgs 1.14µs ± 1% 1.10µs ± 2% -3.55% (p=0.000 n=62+62)
GobDecode 8.88ms ± 2% 8.74ms ± 1% -1.55% (p=0.000 n=66+62)
GobEncode 6.84ms ± 2% 6.61ms ± 2% -3.32% (p=0.000 n=61+67)
Gzip 356ms ± 2% 352ms ± 2% -1.07% (p=0.000 n=67+66)
Gunzip 90.6ms ± 2% 89.8ms ± 1% -0.83% (p=0.000 n=65+64)
HTTPClientServer 82.6µs ± 2% 82.5µs ± 2% ~ (p=0.832 n=65+63)
JSONEncode 17.5ms ± 2% 16.8ms ± 2% -3.77% (p=0.000 n=63+63)
JSONDecode 63.3ms ± 2% 59.0ms ± 2% -6.85% (p=0.000 n=64+63)
Mandelbrot200 3.85ms ± 1% 3.85ms ± 1% ~ (p=0.127 n=65+62)
GoParse 3.75ms ± 2% 3.66ms ± 2% -2.39% (p=0.000 n=66+64)
RegexpMatchEasy0_32 100ns ± 2% 100ns ± 1% -0.65% (p=0.000 n=62+64)
RegexpMatchEasy0_1K 342ns ± 1% 341ns ± 1% -0.43% (p=0.000 n=65+64)
RegexpMatchEasy1_32 82.8ns ± 2% 82.8ns ± 2% ~ (p=0.977 n=63+64)
RegexpMatchEasy1_1K 511ns ± 2% 506ns ± 2% -1.01% (p=0.000 n=63+64)
RegexpMatchMedium_32 139ns ± 1% 134ns ± 3% -3.27% (p=0.000 n=59+60)
RegexpMatchMedium_1K 41.8µs ± 2% 40.5µs ± 2% -3.05% (p=0.000 n=62+64)
RegexpMatchHard_32 2.13µs ± 1% 2.09µs ± 1% -2.22% (p=0.000 n=60+65)
RegexpMatchHard_1K 64.4µs ± 3% 62.8µs ± 2% -2.58% (p=0.000 n=65+59)
Revcomp 531ms ± 2% 529ms ± 1% -0.28% (p=0.022 n=61+61)
Template 73.2ms ± 1% 73.1ms ± 1% ~ (p=0.794 n=66+63)
TimeParse 369ns ± 1% 352ns ± 1% -4.68% (p=0.000 n=65+66)
TimeFormat 374ns ± 2% 348ns ± 2% -7.01% (p=0.000 n=66+64)
Change-Id: Ib190b5bb48a3e9087711d9e3383621d3103dd342
Reviewed-on: https://go-review.googlesource.com/10367
Reviewed-by: Russ Cox <rsc@golang.org>
This commit is contained in:
Josh Bleecher Snyder
parent
2db587c029
commit
f4b48de3ad
@ -497,9 +497,8 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
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p = load_g_cx(ctxt, p) // load g into CX
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p = load_g_cx(ctxt, p) // load g into CX
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}
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}
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var q *obj.Prog
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if cursym.Text.From3Offset()&obj.NOSPLIT == 0 {
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if cursym.Text.From3Offset()&obj.NOSPLIT == 0 {
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p = stacksplit(ctxt, p, autoffset, int32(textarg), &q) // emit split check
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p = stacksplit(ctxt, p, autoffset, int32(textarg)) // emit split check
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}
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}
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if autoffset != 0 {
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if autoffset != 0 {
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@ -524,9 +523,6 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
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p.Spadj = int32(ctxt.Arch.Ptrsize)
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p.Spadj = int32(ctxt.Arch.Ptrsize)
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}
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}
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if q != nil {
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q.Pcond = p
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}
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deltasp := autoffset
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deltasp := autoffset
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if bpsize > 0 {
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if bpsize > 0 {
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@ -856,9 +852,7 @@ func load_g_cx(ctxt *obj.Link, p *obj.Prog) *obj.Prog {
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// Appends to (does not overwrite) p.
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// Appends to (does not overwrite) p.
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// Assumes g is in CX.
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// Assumes g is in CX.
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// Returns last new instruction.
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// Returns last new instruction.
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// On return, *jmpok is the instruction that should jump
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func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32, textarg int32) *obj.Prog {
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// to the stack frame allocation if no split is needed.
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func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32, textarg int32, jmpok **obj.Prog) *obj.Prog {
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cmp := ACMPQ
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cmp := ACMPQ
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lea := ALEAQ
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lea := ALEAQ
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mov := AMOVQ
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mov := AMOVQ
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@ -973,37 +967,39 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32, textarg int32, jmp
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}
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}
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// common
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// common
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p = obj.Appendp(ctxt, p)
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jls := obj.Appendp(ctxt, p)
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jls.As = AJLS
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jls.To.Type = obj.TYPE_BRANCH
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p.As = AJHI
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var last *obj.Prog
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p.To.Type = obj.TYPE_BRANCH
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for last = ctxt.Cursym.Text; last.Link != nil; last = last.Link {
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q := p
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p = obj.Appendp(ctxt, p)
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p.As = obj.ACALL
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p.To.Type = obj.TYPE_BRANCH
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if ctxt.Cursym.Cfunc != 0 {
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p.To.Sym = obj.Linklookup(ctxt, "runtime.morestackc", 0)
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} else if ctxt.Cursym.Text.From3Offset()&obj.NEEDCTXT == 0 {
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p.To.Sym = obj.Linklookup(ctxt, "runtime.morestack_noctxt", 0)
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} else {
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p.To.Sym = obj.Linklookup(ctxt, "runtime.morestack", 0)
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}
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}
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p = obj.Appendp(ctxt, p)
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call := obj.Appendp(ctxt, last)
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p.As = obj.AJMP
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call.Lineno = ctxt.Cursym.Text.Lineno
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p.To.Type = obj.TYPE_BRANCH
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call.Mode = ctxt.Cursym.Text.Mode
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p.Pcond = ctxt.Cursym.Text.Link
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call.As = obj.ACALL
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call.To.Type = obj.TYPE_BRANCH
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if q != nil {
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morestack := "runtime.morestack"
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q.Pcond = p.Link
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switch {
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case ctxt.Cursym.Cfunc != 0:
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morestack = "runtime.morestackc"
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case ctxt.Cursym.Text.From3Offset()&obj.NEEDCTXT == 0:
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morestack = "runtime.morestack_noctxt"
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}
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}
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call.To.Sym = obj.Linklookup(ctxt, morestack, 0)
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jmp := obj.Appendp(ctxt, call)
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jmp.As = obj.AJMP
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jmp.To.Type = obj.TYPE_BRANCH
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jmp.Pcond = ctxt.Cursym.Text.Link
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jls.Pcond = call
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if q1 != nil {
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if q1 != nil {
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q1.Pcond = q.Link
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q1.Pcond = call
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}
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}
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*jmpok = q
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return jls
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return p
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}
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}
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func follow(ctxt *obj.Link, s *obj.LSym) {
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func follow(ctxt *obj.Link, s *obj.LSym) {
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