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Infer flat word structs in Plan 9 asm signatures #43

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34a93b2
plan9asm: translate word-sized struct parameters in ABI0 wrappers
cpunion Sep 29, 2026
0e093ca
test: cover word-struct ABI layout rejection guards
cpunion Sep 29, 2026
a3670da
ci: refresh compress and lz4 assembly corpus pins
cpunion Sep 29, 2026
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5 changes: 3 additions & 2 deletions amd64_translate.go
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Original file line number Diff line number Diff line change
Expand Up @@ -261,9 +261,10 @@ func (c *amd64Ctx) lowerInstr(bi int, ii int, ins Instr, emitBr amd64EmitBr, emi
return true, fmt.Errorf("amd64 RET expects at most 1 operand: %q", ins.Raw)
}
return true, c.lowerRET()
case "PCALIGN", "NO_LOCAL_POINTERS", "PCDATA", "FUNCDATA", "NOP",
case "PCALIGN", "GO_ARGS", "NO_LOCAL_POINTERS", "PCDATA", "FUNCDATA", "NOP",
"PUSH_REGS_HOST_TO_ABI0()", "POP_REGS_HOST_TO_ABI0()":
// Alignment directive emitted by stdlib asm; no semantic effect in our IR.
// Go assembler metadata (including GO_ARGS's argument pointer map) has
// no machine-code effect here; LLVM handles the argument values directly.
return false, nil
case "ADJSP":
if c.goarch != "386" {
Expand Down
4 changes: 2 additions & 2 deletions doc/plan9asm-corpus.md
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Original file line number Diff line number Diff line change
Expand Up @@ -210,7 +210,7 @@ silently include a nested `/v2` module that happens to share its import prefix.
The currently tracked reports are:

- `xgo-dev/llgo#2464`: `github.com/coder/websocket v1.8.15`
- `xgo-dev/llgo#2552`: `github.com/klauspost/compress v1.20.0`
- `xgo-dev/llgo#2552`: `github.com/klauspost/compress v1.20.1`
- `xgo-dev/llgo#2576`: `github.com/tmthrgd/go-hex` at its latest pseudo-version

The ecosystem scan also pins these latest modules:
Expand All @@ -229,7 +229,7 @@ The ecosystem scan also pins these latest modules:
- `github.com/klauspost/reedsolomon v1.14.2`
- `github.com/minio/highwayhash v1.0.4`
- `github.com/modern-go/gls v0.0.0-20250215024828-78308f6bb19d`
- `github.com/pierrec/lz4/v4 v4.1.30`
- `github.com/pierrec/lz4/v4 v4.1.31`
- `github.com/stevvooe/resumable v0.0.0-20180830230917-22b14a53ba50`
- `github.com/tmthrgd/go-bitwise v0.0.0-20190904053232-1430ee983fca`
- `github.com/tmthrgd/go-popcount v0.0.0-20190904054823-afb1ace8b04f`
Expand Down
46 changes: 46 additions & 0 deletions go_translate.go
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Expand Up @@ -779,6 +779,13 @@ func goLLVMTypeForTypeWithSizes(t types.Type, goarch string, sz types.Sizes) (LL
if tt.NumFields() == 0 {
return LLVMType("[0 x i8]"), nil
}
if parts, ok := goWordStructParts(tt, goarch, sz, sz); ok {

@fennoai fennoai Bot Sep 29, 2026

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The aggregate LLVM type here is derived from a second, value-only goWordStructParts call. But on the non-flatten argument path in goLLVMArgsAndFrameSlotsForTuple, goFramePartsForTypeWithSizes has already run goWordStructParts and produced parts whose .Type fields are exactly these element types — so the struct type is classified and each field re-lowered twice per struct argument.

Beyond the duplicate compile-time work, this creates an implicit coupling: the arg path stays correct only because goWordStructParts requires word(sz) == word(frameSz), so the value-only call agrees with the frame-aware one. If that guard is ever relaxed (e.g. to allow value-word != frame-word structs), the aggregate type and the frame layout could silently diverge. Consider building the LLVM aggregate string from the already-computed parts in the non-flatten branch instead of recomputing via a separate value-only call.

fields := make([]string, len(parts))
for i, part := range parts {
fields[i] = string(part.Type)
}
return LLVMType("{ " + strings.Join(fields, ", ") + " }"), nil
}
return "", fmt.Errorf("unsupported struct type %s", tt.String())
case *types.Named:
return goLLVMTypeForTypeWithSizes(tt.Underlying(), goarch, sz)
Expand Down Expand Up @@ -829,6 +836,9 @@ func goLLVMArgsAndFrameSlotsForTuple(tup *types.Tuple, goarch string, sz, frameS
off += int64(frameSz.Sizeof(t))
continue
}
if st, ok := t.Underlying().(*types.Struct); ok && st.NumFields() != 0 {
return nil, nil, 0, fmt.Errorf("unsupported struct frame layout %s", t.String())
}

ty, e := goLLVMTypeForTypeWithSizes(t, goarch, sz)
if e != nil {
Expand Down Expand Up @@ -868,10 +878,46 @@ func goFramePartsForTypeWithSizes(t types.Type, goarch string, sz, frameSz types
return []goFramePart{{Offset: 0, Type: Ptr, Field: 0}, {Offset: word, Type: wordTy, Field: 1}, {Offset: 2 * word, Type: wordTy, Field: 2}}, true
case *types.Interface:
return []goFramePart{{Offset: 0, Type: Ptr, Field: 0}, {Offset: word, Type: Ptr, Field: 1}}, true
case *types.Struct:
return goWordStructParts(u, goarch, sz, frameSz)
}
return nil, false
}

// goWordStructParts accepts only flat structures whose fields are exactly one
// integer/pointer word each in both the Go value and the assembly FP frame.
// Other structures need target-specific padding and register classification.
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// Even word-sized nested structs are rejected: supporting them would require
// recursive flattening and nested field-index mapping instead of a single Field.
func goWordStructParts(st *types.Struct, goarch string, sz, frameSz types.Sizes) ([]goFramePart, bool) {
word := int64(goWordSizeForSizes(goarch, sz))
if st.NumFields() == 0 || word != int64(goWordSizeForSizes(goarch, frameSz)) {
return nil, false
}
fields := make([]*types.Var, st.NumFields())
for i := range fields {
fields[i] = st.Field(i)
}
valueOffsets := sz.Offsetsof(fields)
frameOffsets := frameSz.Offsetsof(fields)
if sz.Sizeof(st) != int64(len(fields))*word || frameSz.Sizeof(st) != int64(len(fields))*word {
return nil, false
}
parts := make([]goFramePart, len(fields))
for i, field := range fields {
if valueOffsets[i] != int64(i)*word || frameOffsets[i] != int64(i)*word ||
sz.Sizeof(field.Type()) != word || frameSz.Sizeof(field.Type()) != word {
return nil, false
}
ty, err := goLLVMTypeForTypeWithSizes(field.Type(), goarch, sz)
if err != nil || (ty != I32 && ty != I64 && ty != Ptr) {
return nil, false
}
parts[i] = goFramePart{Offset: frameOffsets[i], Type: ty, Field: i}
}
return parts, true
}

func goWordSize(goarch string) int {
switch goarch {
case "amd64", "arm64", "wasm":
Expand Down
93 changes: 92 additions & 1 deletion go_translate_deep_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -6,8 +6,11 @@ import (
"go/parser"
"go/token"
"go/types"
"reflect"
"strings"
"testing"

"github.com/xgo-dev/llvm"
)

func mustGoPackageWithImports(t *testing.T, pkgPath string, files map[string]string) GoPackage {
Expand Down Expand Up @@ -135,7 +138,8 @@ func TestGoTranslateTypeCoverage(t *testing.T) {
{alias, "arm64", I64, true},
{types.Typ[types.Complex64], "amd64", "", false},
{types.NewStruct(nil, nil), "amd64", LLVMType("[0 x i8]"), true},
{types.NewStruct([]*types.Var{types.NewVar(token.NoPos, nil, "x", types.Typ[types.Int])}, nil), "amd64", "", false},
{types.NewStruct([]*types.Var{types.NewVar(token.NoPos, nil, "x", types.Typ[types.Int])}, nil), "amd64", "{ i64 }", true},
{types.NewStruct([]*types.Var{types.NewVar(token.NoPos, nil, "x", types.Typ[types.Int8])}, nil), "amd64", "", false},
} {
got, err := goLLVMTypeForType(tc.typ, tc.goarch)
if (err == nil) != tc.ok || got != tc.want {
Expand Down Expand Up @@ -179,6 +183,93 @@ func TestGoTranslateTypeCoverage(t *testing.T) {
}
}

func TestGoTranslateWordStructABI(t *testing.T) {
pkg := mustGoPackage(t, "test/pkg", `package testpkg
type Uint128 struct { Lo, Hi uint64 }
func Y(t *byte, a, b Uint128, res uintptr) int32
func X(t *byte, a, b Uint128, res uintptr) int32
`)
fn := pkg.Types.Scope().Lookup("Y").(*types.Func)
sz := types.SizesFor("gc", "amd64")
sig, err := goFuncSigForDeclaredFunc("test/pkg.Y", fn, "amd64", sz, sz, true)
if err != nil {
t.Fatal(err)
}
if want := []LLVMType{Ptr, "{ i64, i64 }", "{ i64, i64 }", I64}; !reflect.DeepEqual(sig.Args, want) {
t.Fatalf("args = %v, want %v", sig.Args, want)
}
if want := []FrameSlot{
{Offset: 0, Type: Ptr, Index: 0, Field: -1},
{Offset: 8, Type: I64, Index: 1, Field: 0},
{Offset: 16, Type: I64, Index: 1, Field: 1},
{Offset: 24, Type: I64, Index: 2, Field: 0},
{Offset: 32, Type: I64, Index: 2, Field: 1},
{Offset: 40, Type: I64, Index: 3, Field: -1},
}; !reflect.DeepEqual(sig.Frame.Params, want) {
t.Fatalf("frame params = %v, want %v", sig.Frame.Params, want)
}
if want := []FrameSlot{{Offset: 48, Type: I32, Index: 0, Field: -1}}; !reflect.DeepEqual(sig.Frame.Results, want) {
t.Fatalf("frame results = %v, want %v", sig.Frame.Results, want)
}
if _, err := goFuncSigForDeclaredFunc("test/pkg.Y", fn, "386", types.SizesFor("gc", "386"), nil, true); err == nil {
t.Fatal("Uint128 must not be flattened into 32-bit frame words")
}

tr, err := TranslateGoModule(pkg, []byte(`TEXT ·Y(SB),$56-52
GO_ARGS
NO_LOCAL_POINTERS
MOVQ t+0(FP), AX
MOVQ AX, 0(SP)
MOVQ a_Lo+8(FP), AX
MOVQ AX, 8(SP)
MOVQ a_Hi+16(FP), AX
MOVQ AX, 16(SP)
MOVQ b_Lo+24(FP), AX
MOVQ AX, 24(SP)
MOVQ b_Hi+32(FP), AX
MOVQ AX, 32(SP)
MOVQ res+40(FP), AX
MOVQ AX, 40(SP)
CALL ·X(SB)
MOVL 48(SP), AX
MOVL AX, ret+48(FP)
RET
`), GoModuleOptions{GOARCH: "amd64", TargetTriple: "x86_64-unknown-linux-gnu", ResolveSym: testResolveSym("test/pkg")})
if err != nil {
t.Fatal(err)
}
defer tr.Module.Dispose()
if err := llvm.VerifyModule(tr.Module, llvm.ReturnStatusAction); err != nil {
t.Fatalf("invalid LLVM IR: %v", err)
}
ir := tr.Module.String()
if !strings.Contains(ir, "extractvalue { i64, i64 } %arg1, 0") || !strings.Contains(ir, "extractvalue { i64, i64 } %arg2, 1") || !strings.Contains(ir, "call i32 @\"test/pkg.X\"") {
t.Fatalf("missing aggregate argument forwarding in LLVM IR:\n%s", ir)
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cpunion marked this conversation as resolved.
}
}

func TestGoTranslateWordStructGuards(t *testing.T) {
for _, tc := range []struct {
name, arg, frameArch string
}{
{"padding", "struct { a uint8; b uint64 }", "amd64"},
{"subword", "struct { a, b uint32 }", "amd64"},
{"nested", "struct { inner struct { x uint64 } }", "amd64"},
{"float", "struct { x float64 }", "amd64"},
{"frame-word-mismatch", "struct { x uintptr }", "386"},
} {
t.Run(tc.name, func(t *testing.T) {
pkg := mustGoPackage(t, "test/pkg", "package testpkg\nfunc F(x "+tc.arg+")")
fn := pkg.Types.Scope().Lookup("F").(*types.Func)
sz := types.SizesFor("gc", "amd64")
frameSz := types.SizesFor("gc", tc.frameArch)
if _, err := goFuncSigForDeclaredFunc("test/pkg.F", fn, "amd64", sz, frameSz, true); err == nil || !strings.Contains(err.Error(), "unsupported struct") {
t.Fatalf("expected unsupported struct layout, got %v", err)
}
})
}
}

func TestGoTranslateSignatureCoverage(t *testing.T) {
pkg := mustGoPackage(t, "test/pkg", `package testpkg
type S struct{}
Expand Down
4 changes: 2 additions & 2 deletions testdata/corpus/go.mod
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Original file line number Diff line number Diff line change
Expand Up @@ -13,13 +13,13 @@ require (
github.com/dgryski/go-bits v0.0.0-20180113010104-bd8a69a71dc2
github.com/dgryski/go-marvin32 v0.0.0-20240117220238-0d39e8c5a8a9
github.com/golang/snappy v1.0.0
github.com/klauspost/compress v1.20.0
github.com/klauspost/compress v1.20.1
github.com/klauspost/cpuid v1.3.1
github.com/klauspost/cpuid/v2 v2.4.0
github.com/klauspost/reedsolomon v1.14.2
github.com/minio/highwayhash v1.0.4
github.com/modern-go/gls v0.0.0-20250215024828-78308f6bb19d
github.com/pierrec/lz4/v4 v4.1.30
github.com/pierrec/lz4/v4 v4.1.31
github.com/stevvooe/resumable v0.0.0-20180830230917-22b14a53ba50
github.com/tmthrgd/go-bitwise v0.0.0-20190904053232-1430ee983fca
github.com/tmthrgd/go-hex v0.0.0-20190904060850-447a3041c3bc
Expand Down
4 changes: 4 additions & 0 deletions testdata/corpus/go.sum
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,8 @@ github.com/golang/snappy v1.0.0 h1:Oy607GVXHs7RtbggtPBnr2RmDArIsAefDwvrdWvRhGs=
github.com/golang/snappy v1.0.0/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
github.com/klauspost/compress v1.20.0 h1:a3C1ke2ohxFymNlb2HWAHjDeKCI90scRskErZkR0ezA=
github.com/klauspost/compress v1.20.0/go.mod h1:LUdAzn7YLVvxLpc7y3V1m40wESHTgc1422pwwBSKYuI=
github.com/klauspost/compress v1.20.1 h1:T7kKElXUMXrUJ2E9QhQhxFtcK5rPyLdsGZvdbLMPdiQ=
github.com/klauspost/compress v1.20.1/go.mod h1:LUdAzn7YLVvxLpc7y3V1m40wESHTgc1422pwwBSKYuI=
github.com/klauspost/cpuid v1.3.1 h1:5JNjFYYQrZeKRJ0734q51WCEEn2huer72Dc7K+R/b6s=
github.com/klauspost/cpuid v1.3.1/go.mod h1:bYW4mA6ZgKPob1/Dlai2LviZJO7KGI3uoWLd42rAQw4=
github.com/klauspost/cpuid/v2 v2.4.0 h1:S6Hrbc7+ywsr0r+RLapfGBHfyefhCTwEh3A0tV913Dw=
Expand All @@ -43,6 +45,8 @@ github.com/pierrec/lz4/v4 v4.1.29 h1:CDQY6qZOLI4DW0Nx6R1vRrifrCeQHnNXkMb0hZWXFjg
github.com/pierrec/lz4/v4 v4.1.29/go.mod h1:EoQMVJgeeEOMsCqCzqFm2O0cJvljX2nGZjcRIPL34O4=
github.com/pierrec/lz4/v4 v4.1.30 h1:cchX8N2DVP668WkElI9QMwVyoNabLkq1LofDHFeIrdg=
github.com/pierrec/lz4/v4 v4.1.30/go.mod h1:EoQMVJgeeEOMsCqCzqFm2O0cJvljX2nGZjcRIPL34O4=
github.com/pierrec/lz4/v4 v4.1.31 h1:TI8ck6XSudzSzotzAmy0+kh/KpRHaVsKLPzS97gRyNg=
github.com/pierrec/lz4/v4 v4.1.31/go.mod h1:7SE9MC2STkNtL4PIwGhjmyVwvILaGI9/COYQNBhKM/c=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
Expand Down
25 changes: 17 additions & 8 deletions testdata/corpus/reported-libraries.json
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Expand Up @@ -56,7 +56,7 @@
"https://github.com/xgo-dev/llgo/issues/2552"
],
"module": "github.com/klauspost/compress",
"version": "v1.20.0",
"version": "v1.20.1",
"inventory": {
"darwin/amd64": {
"asm_files": 8,
Expand Down Expand Up @@ -360,11 +360,14 @@
"id": "pierrec-lz4-v4",
"origin": "ecosystem-scan",
"module": "github.com/pierrec/lz4/v4",
"version": "v4.1.30",
"version": "v4.1.31",
"inventory": {
"darwin/amd64": {
"asm_files": 1,
"packages": ["github.com/pierrec/lz4/v4/internal/lz4block"]
"asm_files": 2,
"packages": [
"github.com/pierrec/lz4/v4/internal/lz4block",
"github.com/pierrec/lz4/v4/internal/xxh32"
]
},
"darwin/arm64": {
"asm_files": 2,
Expand All @@ -374,8 +377,11 @@
]
},
"linux/amd64": {
"asm_files": 1,
"packages": ["github.com/pierrec/lz4/v4/internal/lz4block"]
"asm_files": 2,
"packages": [
"github.com/pierrec/lz4/v4/internal/lz4block",
"github.com/pierrec/lz4/v4/internal/xxh32"
]
},
"linux/arm": {
"asm_files": 2,
Expand All @@ -392,8 +398,11 @@
]
},
"windows/amd64": {
"asm_files": 1,
"packages": ["github.com/pierrec/lz4/v4/internal/lz4block"]
"asm_files": 2,
"packages": [
"github.com/pierrec/lz4/v4/internal/lz4block",
"github.com/pierrec/lz4/v4/internal/xxh32"
]
},
"windows/arm64": {
"asm_files": 2,
Expand Down
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