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cmd/compile/internal/ssa: handle more cases in fuse pass
Currently fuseBlockIf handls four cases where s0 and s1 have only one predecessor
node. In fact, even if s0 and s1 have multiple predecessor nodes, it can be optimized
as well. This patch handles these cases.
This CL does not bring significant performance changes, it is more like an optimization
of dead code elimination. So it detects a lot of benchmarks whose functions are
completely optimized, such as BenchmarkNeIfaceConcrete, BenchmarkEqIfaceConcrete,
BenchmarkFullJapaneseRune, BenchmarkClearFat{8, 12, 16,...1024}, Benchmark{En|De}codeRune,
and BenchmarkCopyFat{8, 12, 16,...1024} and many others that I didn't check.
Test result of compilecmp on linux amd64, the data on linux arm64 is similar.
name old time/op new time/op delta
Template 466131893.640000ns +-16% 455546571.480000ns +-12% ~ (p=0.066 n=50+50)
Unicode 195858206.980000ns +- 9% 197387526.224490ns +- 9% ~ (p=0.231 n=50+49)
GoTypes 1581961264.260000ns +- 7% 1581828319.640000ns +- 5% ~ (p=0.964 n=50+50)
Compiler 7425890449.259998ns +- 2% 7424138343.632654ns +- 2% ~ (p=0.815 n=50+49)
SSA 17392652203.380009ns +- 1% 17248314507.854172ns +- 1% -0.83% (p=0.000 n=50+48)
Flate 298061504.940000ns +-12% 292773080.632653ns +-12% ~ (p=0.165 n=50+49)
GoParser 376046929.420000ns +- 9% 370746254.693878ns +- 9% ~ (p=0.231 n=50+49)
Reflect 995721330.160000ns +- 7% 985916024.620000ns +- 7% ~ (p=0.103 n=50+50)
Tar 398878287.040000ns +-10% 399186737.000000ns +-11% ~ (p=0.883 n=50+50)
XML 555898064.200000ns +- 8% 554877077.100000ns +-10% ~ (p=0.926 n=50+50)
LinkCompiler 757995424.632653ns +- 7% 758301900.420000ns +- 7% ~ (p=0.437 n=49+50)
ExternalLinkCompiler 2399985741.270834ns +- 4% 2396112274.630435ns +- 4% ~ (p=0.766 n=48+46)
LinkWithoutDebugCompiler 450472710.700000ns +- 9% 448935188.720000ns +- 7% ~ (p=0.668 n=50+50)
[Geo mean] 927951041.671984ns 922858781.007286ns -0.55%
name old user-time/op new user-time/op delta
Template 639484500.000000ns +-16% 630857140.000000ns +-13% ~ (p=0.363 n=50+50)
Unicode 370072081.632653ns +-11% 375108300.000000ns +-10% ~ (p=0.248 n=49+50)
GoTypes 2205838860.000000ns +- 5% 2206640900.000000ns +- 3% ~ (p=0.915 n=50+50)
Compiler 10337224272.727268ns +- 2% 10366187152.173916ns +- 2% ~ (p=0.324 n=44+46)
SSA 23843616104.166660ns +- 3% 23678281387.755112ns +- 3% -0.69% (p=0.002 n=48+49)
Flate 396446760.000000ns +-15% 391245333.333333ns +-10% ~ (p=0.313 n=50+48)
GoParser 509121660.000000ns +-10% 505938620.000000ns +- 9% ~ (p=0.436 n=50+50)
Reflect 1328136212.765958ns +- 6% 1312627440.000000ns +- 8% ~ (p=0.068 n=47+50)
Tar 563039480.000000ns +-10% 563064360.000000ns +-10% ~ (p=0.953 n=50+50)
XML 775596380.000000ns +- 9% 774736920.000000ns +-11% ~ (p=0.899 n=50+50)
LinkCompiler 1315155260.000000ns +- 9% 1312946860.000001ns +- 6% ~ (p=0.861 n=50+50)
ExternalLinkCompiler 2739635480.000000ns +- 6% 2732580380.000000ns +- 6% ~ (p=0.943 n=50+50)
LinkWithoutDebugCompiler 537418600.000000ns +-10% 535914620.000000ns +- 9% ~ (p=0.734 n=50+50)
[Geo mean] 1296231259.389525ns 1291929605.124197ns -0.33%
name old alloc/op new alloc/op delta
Template 35.0MB +- 0% 35.0MB +- 0% ~ (p=0.586 n=50+50)
Unicode 29.3MB +- 0% 29.3MB +- 0% +0.01% (p=0.004 n=50+50)
GoTypes 116MB +- 0% 116MB +- 0% ~ (p=0.102 n=50+50)
Compiler 555MB +- 0% 555MB +- 0% ~ (p=0.285 n=50+50)
SSA 1.37GB +- 0% 1.36GB +- 0% -0.98% (p=0.000 n=49+49)
Flate 21.8MB +- 0% 21.8MB +- 0% ~ (p=0.475 n=50+49)
GoParser 26.7MB +- 0% 26.7MB +- 0% ~ (p=0.385 n=50+50)
Reflect 74.2MB +- 0% 74.3MB +- 0% +0.01% (p=0.006 n=49+50)
Tar 32.7MB +- 0% 32.7MB +- 0% ~ (p=0.125 n=50+50)
XML 41.8MB +- 0% 41.8MB +- 0% ~ (p=0.649 n=49+50)
LinkCompiler 105MB +- 0% 105MB +- 0% -0.05% (p=0.000 n=50+48)
ExternalLinkCompiler 92.6MB +- 0% 92.6MB +- 0% -0.02% (p=0.000 n=50+50)
LinkWithoutDebugCompiler 63.9MB +- 0% 63.9MB +- 0% -0.05% (p=0.000 n=50+50)
[Geo mean] 77.0MB 76.9MB -0.08%
name old allocs/op new allocs/op delta
Template 344k +- 0% 344k +- 0% ~ (p=0.091 n=50+50)
Unicode 340k +- 0% 340k +- 0% ~ (p=0.084 n=50+50)
GoTypes 1.19M +- 0% 1.19M +- 0% ~ (p=0.634 n=50+50)
Compiler 5.05M +- 0% 5.05M +- 0% ~ (p=0.428 n=50+48)
SSA 12.9M +- 0% 12.8M +- 0% -0.94% (p=0.000 n=48+50)
Flate 216k +- 0% 216k +- 0% ~ (p=0.959 n=50+50)
GoParser 275k +- 0% 275k +- 0% ~ (p=0.705 n=50+50)
Reflect 887k +- 0% 887k +- 0% ~ (p=0.136 n=50+50)
Tar 318k +- 0% 318k +- 0% +0.01% (p=0.007 n=50+48)
XML 396k +- 0% 396k +- 0% ~ (p=0.577 n=48+50)
LinkCompiler 457k +- 0% 457k +- 0% -0.02% (p=0.000 n=50+48)
ExternalLinkCompiler 459k +- 0% 459k +- 0% -0.02% (p=0.000 n=50+49)
LinkWithoutDebugCompiler 111k +- 0% 111k +- 0% -0.09% (p=0.000 n=50+50)
[Geo mean] 603k 603k -0.08%
name old maxRSS/op new maxRSS/op delta
Template 33.7M +- 5% 33.7M +- 3% ~ (p=0.798 n=50+48)
Unicode 35.2M +- 5% 35.3M +- 5% ~ (p=0.586 n=50+50)
GoTypes 73.5M +- 5% 73.2M +- 5% ~ (p=0.436 n=50+50)
Compiler 315M +- 3% 315M +- 3% ~ (p=0.726 n=49+48)
SSA 705M +- 5% 691M +- 5% -2.01% (p=0.000 n=50+50)
Flate 25.2M +- 3% 25.0M +- 3% ~ (p=0.122 n=49+49)
GoParser 27.7M +- 5% 27.7M +- 3% ~ (p=0.967 n=50+50)
Reflect 54.6M +- 4% 54.8M +- 4% ~ (p=0.418 n=50+50)
Tar 32.2M +- 4% 32.1M +- 3% ~ (p=0.644 n=50+49)
XML 38.7M +- 5% 38.9M +- 5% ~ (p=0.612 n=50+50)
LinkCompiler 159M +- 1% 159M +- 1% ~ (p=0.302 n=49+50)
ExternalLinkCompiler 171M +- 1% 170M +- 1% -0.33% (p=0.000 n=50+50)
LinkWithoutDebugCompiler 133M +- 1% 132M +- 1% -0.44% (p=0.000 n=48+50)
[Geo mean] 76.9M 76.8M -0.25%
name old text-bytes new text-bytes delta
HelloSize 804kB +- 0% 804kB +- 0% ~ (all equal)
name old data-bytes new data-bytes delta
HelloSize 13.2kB +- 0% 13.2kB +- 0% ~ (all equal)
name old bss-bytes new bss-bytes delta
HelloSize 206kB +- 0% 206kB +- 0% ~ (all equal)
name old exe-bytes new exe-bytes delta
HelloSize 1.20MB +- 0% 1.20MB +- 0% ~ (all equal)
file before after Δ %
api 4904729 4904881 +152 +0.003%
asm 4849768 4849696 -72 -0.001%
buildid 2604760 2604768 +8 +0.000%
cgo 4505984 4506000 +16 +0.000%
compile 18936732 18864939 -71793 -0.379%
cover 4787385 4787377 -8 -0.000%
dist 3451964 3451988 +24 +0.001%
doc 3794929 3794913 -16 -0.000%
fix 3201863 3201847 -16 -0.000%
link 6467231 6467327 +96 +0.001%
objdump 4400076 4400132 +56 +0.001%
pprof 13354395 13354507 +112 +0.001%
trace 10186673 10187273 +600 +0.006%
vet 6727213 6727277 +64 +0.001%
total 105284348 105213571 -70777 -0.067%
Change-Id: I5020d112021f165a4ae18aa56402d8690330d8fb
Reviewed-on: https://go-review.googlesource.com/c/go/+/239457
Reviewed-by: eric fang <eric.fang@arm.com>
Reviewed-by: Keith Randall <khr@golang.org>
Trust: eric fang <eric.fang@arm.com>
Run-TryBot: eric fang <eric.fang@arm.com>
TryBot-Result: Go Bot <gobot@golang.org>
This commit is contained in:
eric fang
parent
15f16706fb
commit
051bf37833
@ -51,11 +51,11 @@ func fuse(f *Func, typ fuseType) {
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// fuseBlockIf handles the following cases where s0 and s1 are empty blocks.
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//
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// b b b b
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// / \ | \ / | | |
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// s0 s1 | s1 s0 | | |
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// \ / | / \ | | |
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// ss ss ss ss
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// b b b b
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// \ / \ / | \ / \ / | | |
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// s0 s1 | s1 s0 | | |
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// \ / | / \ | | |
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// ss ss ss ss
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//
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// If all Phi ops in ss have identical variables for slots corresponding to
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// s0, s1 and b then the branch can be dropped.
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@ -69,11 +69,11 @@ func fuseBlockIf(b *Block) bool {
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if b.Kind != BlockIf {
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return false
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}
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// It doesn't matter how much Preds does s0 or s1 have.
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var ss0, ss1 *Block
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s0 := b.Succs[0].b
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i0 := b.Succs[0].i
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if s0.Kind != BlockPlain || len(s0.Preds) != 1 || !isEmpty(s0) {
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if s0.Kind != BlockPlain || !isEmpty(s0) {
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s0, ss0 = b, s0
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} else {
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ss0 = s0.Succs[0].b
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@ -81,15 +81,25 @@ func fuseBlockIf(b *Block) bool {
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}
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s1 := b.Succs[1].b
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i1 := b.Succs[1].i
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if s1.Kind != BlockPlain || len(s1.Preds) != 1 || !isEmpty(s1) {
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if s1.Kind != BlockPlain || !isEmpty(s1) {
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s1, ss1 = b, s1
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} else {
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ss1 = s1.Succs[0].b
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i1 = s1.Succs[0].i
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}
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if ss0 != ss1 {
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return false
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if s0.Kind == BlockPlain && isEmpty(s0) && s1.Kind == BlockPlain && isEmpty(s1) {
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// Two special cases where both s0, s1 and ss are empty blocks.
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if s0 == ss1 {
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s0, ss0 = b, ss1
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} else if ss0 == s1 {
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s1, ss1 = b, ss0
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} else {
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return false
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}
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} else {
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return false
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}
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}
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ss := ss0
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@ -102,48 +112,45 @@ func fuseBlockIf(b *Block) bool {
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}
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}
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// Now we have two of following b->ss, b->s0->ss and b->s1->ss,
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// with s0 and s1 empty if exist.
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// We can replace it with b->ss without if all OpPhis in ss
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// have identical predecessors (verified above).
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// No critical edge is introduced because b will have one successor.
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if s0 != b && s1 != b {
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// Replace edge b->s0->ss with b->ss.
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// We need to keep a slot for Phis corresponding to b.
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b.Succs[0] = Edge{ss, i0}
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ss.Preds[i0] = Edge{b, 0}
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b.removeEdge(1)
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s1.removeEdge(0)
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} else if s0 != b {
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b.removeEdge(0)
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// We do not need to redirect the Preds of s0 and s1 to ss,
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// the following optimization will do this.
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b.removeEdge(0)
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if s0 != b && len(s0.Preds) == 0 {
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s0.removeEdge(0)
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} else if s1 != b {
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b.removeEdge(1)
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s1.removeEdge(0)
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} else {
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b.removeEdge(1)
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// Move any (dead) values in s0 to b,
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// where they will be eliminated by the next deadcode pass.
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for _, v := range s0.Values {
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v.Block = b
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}
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b.Values = append(b.Values, s0.Values...)
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// Clear s0.
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s0.Kind = BlockInvalid
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s0.Values = nil
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s0.Succs = nil
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s0.Preds = nil
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}
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b.Kind = BlockPlain
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b.Likely = BranchUnknown
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b.ResetControls()
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// Trash the empty blocks s0 and s1.
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blocks := [...]*Block{s0, s1}
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for _, s := range &blocks {
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if s == b {
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continue
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// The values in b may be dead codes, and clearing them in time may
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// obtain new optimization opportunities.
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// First put dead values that can be deleted into a slice walkValues.
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// Then put their arguments in walkValues before resetting the dead values
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// in walkValues, because the arguments may also become dead values.
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walkValues := []*Value{}
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for _, v := range b.Values {
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if v.Uses == 0 && v.removeable() {
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walkValues = append(walkValues, v)
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}
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// Move any (dead) values in s0 or s1 to b,
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// where they will be eliminated by the next deadcode pass.
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for _, v := range s.Values {
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v.Block = b
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}
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for len(walkValues) != 0 {
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v := walkValues[len(walkValues)-1]
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walkValues = walkValues[:len(walkValues)-1]
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if v.Uses == 0 && v.removeable() {
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walkValues = append(walkValues, v.Args...)
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v.reset(OpInvalid)
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}
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b.Values = append(b.Values, s.Values...)
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// Clear s.
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s.Kind = BlockInvalid
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s.Values = nil
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s.Succs = nil
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s.Preds = nil
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}
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return true
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}
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@ -104,6 +104,18 @@ func TestFuseHandlesPhis(t *testing.T) {
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func TestFuseEliminatesEmptyBlocks(t *testing.T) {
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c := testConfig(t)
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// Case 1, plain type empty blocks z0 ~ z3 will be eliminated.
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// entry
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// |
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// z0
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// |
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// z1
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// |
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// z2
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// |
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// z3
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// |
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// exit
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fun := c.Fun("entry",
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Bloc("entry",
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Valu("mem", OpInitMem, types.TypeMem, 0, nil),
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@ -126,16 +138,77 @@ func TestFuseEliminatesEmptyBlocks(t *testing.T) {
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for k, b := range fun.blocks {
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if k[:1] == "z" && b.Kind != BlockInvalid {
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t.Errorf("%s was not eliminated, but should have", k)
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t.Errorf("case1 %s was not eliminated, but should have", k)
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}
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}
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// Case 2, empty blocks with If branch, z0 and z1 will be eliminated.
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// entry
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// / \
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// z0 z1
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// \ /
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// exit
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fun = c.Fun("entry",
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Bloc("entry",
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Valu("mem", OpInitMem, types.TypeMem, 0, nil),
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Valu("c", OpArg, c.config.Types.Bool, 0, nil),
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If("c", "z0", "z1")),
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Bloc("z0",
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Goto("exit")),
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Bloc("z1",
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Goto("exit")),
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Bloc("exit",
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Exit("mem"),
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))
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CheckFunc(fun.f)
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fuseLate(fun.f)
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for k, b := range fun.blocks {
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if k[:1] == "z" && b.Kind != BlockInvalid {
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t.Errorf("case2 %s was not eliminated, but should have", k)
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}
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}
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// Case 3, empty blocks with multiple predecessors, z0 and z1 will be eliminated.
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// entry
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// | \
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// | b0
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// | / \
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// z0 z1
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// \ /
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// exit
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fun = c.Fun("entry",
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Bloc("entry",
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Valu("mem", OpInitMem, types.TypeMem, 0, nil),
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Valu("c1", OpArg, c.config.Types.Bool, 0, nil),
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If("c1", "b0", "z0")),
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Bloc("b0",
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Valu("c2", OpArg, c.config.Types.Bool, 0, nil),
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If("c2", "z1", "z0")),
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Bloc("z0",
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Goto("exit")),
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Bloc("z1",
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Goto("exit")),
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Bloc("exit",
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Exit("mem"),
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))
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CheckFunc(fun.f)
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fuseLate(fun.f)
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for k, b := range fun.blocks {
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if k[:1] == "z" && b.Kind != BlockInvalid {
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t.Errorf("case3 %s was not eliminated, but should have", k)
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}
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}
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}
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func TestFuseSideEffects(t *testing.T) {
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// Test that we don't fuse branches that have side effects but
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c := testConfig(t)
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// Case1, test that we don't fuse branches that have side effects but
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// have no use (e.g. followed by infinite loop).
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// See issue #36005.
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c := testConfig(t)
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fun := c.Fun("entry",
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Bloc("entry",
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Valu("mem", OpInitMem, types.TypeMem, 0, nil),
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@ -163,6 +236,31 @@ func TestFuseSideEffects(t *testing.T) {
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t.Errorf("else is eliminated, but should not")
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}
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}
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// Case2, z0 contains a value that has side effect, z0 shouldn't be eliminated.
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// entry
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// | \
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// | z0
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// | /
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// exit
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fun = c.Fun("entry",
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Bloc("entry",
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Valu("mem", OpInitMem, types.TypeMem, 0, nil),
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Valu("c1", OpArg, c.config.Types.Bool, 0, nil),
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Valu("p", OpArg, c.config.Types.IntPtr, 0, nil),
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If("c1", "z0", "exit")),
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Bloc("z0",
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Valu("nilcheck", OpNilCheck, types.TypeVoid, 0, nil, "p", "mem"),
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Goto("exit")),
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Bloc("exit",
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Exit("mem"),
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))
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CheckFunc(fun.f)
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fuseLate(fun.f)
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z0, ok := fun.blocks["z0"]
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if !ok || z0.Kind == BlockInvalid {
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t.Errorf("case2 z0 is eliminated, but should not")
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}
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}
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func BenchmarkFuse(b *testing.B) {
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