Jakub Ciolek (Gerrit)

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Jul 20, 2026, 8:54:43 AM (6 days ago) Jul 20

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Commit message

cmd/compile: order functions by IR node count

Count nodes during the existing pre-walk traversal and use that
count instead of the number of top-level statements when ordering
functions for compilation.

compilebench Intel Alder Lake 12600k (P cores):

                         │ /home/jake/26jul/costmodel.master │   /home/jake/26jul/costmodel.new    │
                         │              sec/op               │   sec/op     vs base                │
Template                                         87.92m ± 1%   88.16m ± 1%        ~ (p=0.341 n=20)
Unicode                                          61.10m ± 1%   61.17m ± 1%        ~ (p=0.429 n=20)
GoTypes                                          544.1m ± 0%   542.9m ± 1%   -0.23% (p=0.046 n=20)
Compiler                                         83.30m ± 1%   81.97m ± 1%   -1.60% (p=0.000 n=20)
SSA                                               5.170 ± 0%    5.061 ± 0%   -2.11% (p=0.000 n=20)
Flate                                            95.04m ± 0%   94.80m ± 0%        ~ (p=0.192 n=20)
GoParser                                         96.25m ± 0%   84.29m ± 1%  -12.43% (p=0.000 n=20)
Reflect                                          229.2m ± 0%   227.6m ± 1%   -0.69% (p=0.000 n=20)
Tar                                             100.23m ± 1%   99.12m ± 0%   -1.11% (p=0.000 n=20)
XML                                              114.7m ± 1%   113.3m ± 0%   -1.29% (p=0.000 n=20)
LinkCompiler                                     286.8m ± 1%   285.6m ± 1%        ~ (p=0.820 n=20)
ExternalLinkCompiler                             760.9m ± 0%   760.8m ± 0%        ~ (p=0.841 n=20)
LinkWithoutDebugCompiler                         182.8m ± 1%   179.5m ± 1%   -1.83% (p=0.000 n=20)
StdCmd                                            36.82 ± 0%    36.60 ± 0%   -0.61% (p=0.001 n=20)
geomean                                          298.5m        293.6m        -1.63%

                         │ /home/jake/26jul/costmodel.master │   /home/jake/26jul/costmodel.new   │
                         │            user-sec/op            │ user-sec/op  vs base               │
Template                                         225.9m ± 1%   225.2m ± 2%       ~ (p=0.846 n=20)
Unicode                                          67.70m ± 4%   67.59m ± 4%       ~ (p=0.841 n=20)
GoTypes                                           1.791 ± 1%    1.775 ± 1%  -0.87% (p=0.038 n=20)
Compiler                                         164.4m ± 2%   163.8m ± 2%       ~ (p=0.142 n=20)
SSA                                               17.56 ± 1%    17.63 ± 1%       ~ (p=0.989 n=20)
Flate                                            269.2m ± 2%   270.1m ± 1%       ~ (p=0.738 n=20)
GoParser                                         232.4m ± 2%   232.0m ± 2%       ~ (p=0.779 n=20)
Reflect                                          644.1m ± 1%   642.5m ± 0%       ~ (p=0.547 n=20)
Tar                                              267.3m ± 1%   261.6m ± 1%  -2.13% (p=0.000 n=20)
XML                                              313.7m ± 1%   304.0m ± 1%  -3.11% (p=0.000 n=20)
LinkCompiler                                     462.1m ± 1%   468.6m ± 1%  +1.41% (p=0.013 n=20)
ExternalLinkCompiler                             848.9m ± 1%   846.6m ± 1%       ~ (p=0.779 n=20)
LinkWithoutDebugCompiler                         213.1m ± 2%   213.3m ± 2%       ~ (p=0.429 n=20)
geomean                                          438.7m        436.9m       -0.43%

Change-Id: I0389d056d5759117b768881f8ac1697f6cab366a

Change diff

diff --git a/src/cmd/compile/internal/gc/compile.go b/src/cmd/compile/internal/gc/compile.go
index 3d8974e..e1867d8 100644
--- a/src/cmd/compile/internal/gc/compile.go
+++ b/src/cmd/compile/internal/gc/compile.go
@@ -148,7 +148,7 @@
 		// Since we remove from the end of the slice queue,
 		// that means shortest to longest.
 		slices.SortFunc(compilequeue, func(a, b *ir.Func) int {
-			return cmp.Compare(len(a.Body), len(b.Body))
+			return cmp.Compare(a.NumPreWalkNodes, b.NumPreWalkNodes)
 		})
 	}
 
diff --git a/src/cmd/compile/internal/ir/func.go b/src/cmd/compile/internal/ir/func.go
index e387927..c6675e2 100644
--- a/src/cmd/compile/internal/ir/func.go
+++ b/src/cmd/compile/internal/ir/func.go
@@ -55,6 +55,11 @@
 	// if you add or remove a field, don't forget to update sizeof_test.go
 
 	miniNode
+
+	// NumPreWalkNodes is the number of IR nodes before Walk.
+	// It is used as an estimate of backend compilation cost.
+	NumPreWalkNodes int32
+
 	Body Nodes
 
 	Nname    *Name        // ONAME node
diff --git a/src/cmd/compile/internal/ir/sizeof_test.go b/src/cmd/compile/internal/ir/sizeof_test.go
index b805155..047de93 100644
--- a/src/cmd/compile/internal/ir/sizeof_test.go
+++ b/src/cmd/compile/internal/ir/sizeof_test.go
@@ -20,7 +20,7 @@
 		_32bit uintptr // size on 32bit platforms
 		_64bit uintptr // size on 64bit platforms
 	}{
-		{Func{}, 184, 312},
+		{Func{}, 188, 312},
 		{Name{}, 96, 160},
 		{miniExpr{}, 32, 48},
 		{miniNode{}, 12, 12},
diff --git a/src/cmd/compile/internal/walk/walk.go b/src/cmd/compile/internal/walk/walk.go
index 68e8545..ac81661 100644
--- a/src/cmd/compile/internal/walk/walk.go
+++ b/src/cmd/compile/internal/walk/walk.go
@@ -471,7 +471,9 @@
 	ro.Init(fn)
 	sv := make(map[ir.Node]ir.Node)
 	scs := make(map[*ir.Name]*types.Type)
+	var numNodes int32
 	ir.Visit(fn, func(n ir.Node) {
+		numNodes++
 		switch n.Op() {
 		case ir.OCONVIFACE:
 			x := n.(*ir.ConvExpr).X
@@ -496,4 +498,5 @@
 	})
 	staticValues = sv
 	shapeConvSources = scs
+	fn.NumPreWalkNodes = numNodes
 }

Change information

Files:

M src/cmd/compile/internal/gc/compile.go
M src/cmd/compile/internal/ir/func.go
M src/cmd/compile/internal/ir/sizeof_test.go
M src/cmd/compile/internal/walk/walk.go

Change size: S

Delta: 4 files changed, 10 insertions(+), 2 deletions(-)

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Jakub Ciolek (Gerrit)

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Jul 20, 2026, 8:55:39 AM (6 days ago) Jul 20

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Michael Matloob (Gerrit)

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Jul 21, 2026, 2:23:38 PM (5 days ago) Jul 21

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Michael Matloob . resolved

Ooh thanks! This looks good! I'll try running benchmarks on some other machines.

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Jul 21, 2026, 5:29:22 PM (5 days ago) Jul 21

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Jul 21, 2026, 10:39:43 PM (5 days ago) Jul 21

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Michael Matloob (Gerrit)

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Jul 21, 2026, 10:48:10 PM (5 days ago) Jul 21

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Michael Matloob . resolved

There's not much of a difference on the amd64 GoBuild sweet benchmarks, but the c4 72 core builder does show a noticeable improvement.

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Jakub Ciolek (Gerrit)

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Jul 22, 2026, 3:51:20 AM (4 days ago) Jul 22

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Michael Matloob . resolved

There's not much of a difference on the amd64 GoBuild sweet benchmarks, but the c4 72 core builder does show a noticeable improvement.

Jakub Ciolek

Thanks for doing the benches, how much of a difference was it on the 72 core one?

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[go] cmd/compile: order functions by IR node count

Jakub Ciolek (Gerrit)

Jakub Ciolek has uploaded the change for review

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Jakub Ciolek (Gerrit)

Jakub Ciolek voted Commit-Queue+1

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Michael Matloob voted and added 1 comment

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Carlos Amedee voted Code-Review+1

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Michael Matloob (Gerrit)

Michael Matloob voted Code-Review+1

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Michael Matloob (Gerrit)

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