Skip to content

[MC][WebAssembly] Fix importing tables with limits #172992

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
daxpedda wants to merge 2 commits into
base: main
Choose a base branch
from
+71 −26
Open

[MC][WebAssembly] Fix importing tables with limits #172992

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
158f4f4
[WebAssembly] fix importing tables with limits
daxpedda Dec 19, 2025
3902053
Fix minimum size of `__indirect_function_table`
daxpedda Dec 21, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
22 changes: 16 additions & 6 deletions llvm/lib/MC/WasmObjectWriter.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -323,8 +323,8 @@ class WasmObjectWriter : public MCObjectWriter {
void writeValueType(wasm::ValType Ty) { W->OS << static_cast<char>(Ty); }

void writeTypeSection(ArrayRef<wasm::WasmSignature> Signatures);
void writeImportSection(ArrayRef<wasm::WasmImport> Imports, uint64_t DataSize,
uint32_t NumElements);
void writeImportSection(ArrayRef<wasm::WasmImport> Imports,
uint64_t DataSize);
void writeFunctionSection(ArrayRef<WasmFunction> Functions);
void writeExportSection(ArrayRef<wasm::WasmExport> Exports);
void writeElemSection(const MCSymbolWasm *IndirectFunctionTable,
Expand Down Expand Up @@ -823,8 +823,7 @@ void WasmObjectWriter::writeTypeSection(
}

void WasmObjectWriter::writeImportSection(ArrayRef<wasm::WasmImport> Imports,
uint64_t DataSize,
uint32_t NumElements) {
uint64_t DataSize) {
if (Imports.empty())
return;

Expand Down Expand Up @@ -855,7 +854,9 @@ void WasmObjectWriter::writeImportSection(ArrayRef<wasm::WasmImport> Imports,
case wasm::WASM_EXTERNAL_TABLE:
W->OS << char(Import.Table.ElemType);
encodeULEB128(Import.Table.Limits.Flags, W->OS);
encodeULEB128(NumElements, W->OS); // initial
encodeULEB128(Import.Table.Limits.Minimum, W->OS);
if (Import.Table.Limits.Flags & wasm::WASM_LIMITS_FLAG_HAS_MAX)
encodeULEB128(Import.Table.Limits.Maximum, W->OS);
break;
case wasm::WASM_EXTERNAL_TAG:
W->OS << char(0); // Reserved 'attribute' field
Expand Down Expand Up @@ -1849,6 +1850,15 @@ uint64_t WasmObjectWriter::writeOneObject(MCAssembler &Asm,
HandleReloc(RelEntry);
for (const WasmRelocationEntry &RelEntry : DataRelocations)
HandleReloc(RelEntry);

// Update minimum size of `__indirect_function_table` table.
auto It = llvm::find_if(Imports, [](const wasm::WasmImport &I) {
return I.Field == "__indirect_function_table";
});
Copy link
Collaborator

@sbc100 sbc100 Dec 22, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

We already lookup this symbol in other places in this file with lookupSymbol("__indirect_function_table"). Can we combine this somehow and avoid this lvm::find_if?

Copy link
Author

@daxpedda daxpedda Dec 22, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

No, because they are looking it up in a different table, not in Imports.


if (It != Imports.end()) {
It->Table.Limits.Minimum = TableElems.size();
}
}

// Translate .init_array section contents into start functions.
Expand Down Expand Up @@ -1901,7 +1911,7 @@ uint64_t WasmObjectWriter::writeOneObject(MCAssembler &Asm,
uint32_t CodeSectionIndex, DataSectionIndex;
if (Mode != DwoMode::DwoOnly) {
writeTypeSection(Signatures);
writeImportSection(Imports, DataSize, TableElems.size());
writeImportSection(Imports, DataSize);
writeFunctionSection(Functions);
writeTableSection(Tables);
// Skip the "memory" section; we import the memory instead.
Expand Down
75 changes: 55 additions & 20 deletions llvm/test/MC/WebAssembly/tables.s
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,10 @@ table1:
table2:
.tabletype table2, funcref, 42, 100

.import_module table3, env
.import_name table3, table3
.tabletype table3, funcref, 42, 100

# Table instructions

# CHECK: copy_tables:
Expand All @@ -28,6 +32,8 @@ table2:
# CHECK-NEXT: local.get 1
# CHECK: table.size table1
# CHECK: table.copy table1, table2
# CHECK: table.size table2
# CHECK: table.copy table2, table3
# CHECK-NEXT: end_function
copy_tables:
.functype copy_tables (i32, i32) -> ()
Expand All @@ -39,6 +45,11 @@ copy_tables:

# ENC: table.copy table1, table2 # encoding: [0xfc,0x0e,0x80'A',0x80'A',0x80'A',0x80'A',A,0x80'B',0x80'B',0x80'B',0x80'B',B]
table.copy table1, table2

local.get 0
local.get 1
table.size table2
table.copy table2, table3
end_function

# CHECK: table_get:
Expand Down Expand Up @@ -109,21 +120,31 @@ table_fill:
table.fill table1
end_function

# BIN: Field: table3
# BIN-NEXT: Kind: TABLE
# BIN-NEXT: Table:
# BIN-NEXT: Index: 0
# BIN-NEXT: ElemType: FUNCREF
# BIN-NEXT: Limits:
# BIN-NEXT: Flags: [ HAS_MAX ]
# BIN-NEXT: Minimum: 0x2A
# BIN-NEXT: Maximum: 0x64

# BIN: - Type: TABLE
# BIN-NEXT: Tables:
# BIN-NEXT: - Index: 0
# BIN-NEXT: - Index: 1
# BIN-NEXT: ElemType: EXTERNREF
# BIN-NEXT: Limits:
# BIN-NEXT: Minimum: 0x0
# BIN-NEXT: - Index: 1
# BIN-NEXT: - Index: 2
# BIN-NEXT: ElemType: FUNCREF
# BIN-NEXT: Limits:
# BIN-NEXT: Minimum: 0x0
# BIN-NEXT: - Index: 2
# BIN-NEXT: - Index: 3
# BIN-NEXT: ElemType: FUNCREF
# BIN-NEXT: Limits:
# BIN-NEXT: Minimum: 0x2A
# BIN-NEXT: - Index: 3
# BIN-NEXT: - Index: 4
# BIN-NEXT: ElemType: FUNCREF
# BIN-NEXT: Limits:
# BIN-NEXT: Flags: [ HAS_MAX ]
Expand All @@ -142,39 +163,48 @@ table_fill:
# BIN-NEXT: Index: 3
# BIN-NEXT: Offset: 0x15
# BIN-NEXT: - Type: R_WASM_TABLE_NUMBER_LEB
# BIN-NEXT: Index: 0
# BIN-NEXT: Index: 3
# BIN-NEXT: Offset: 0x20
# BIN-NEXT: - Type: R_WASM_TABLE_NUMBER_LEB
# BIN-NEXT: Index: 3
# BIN-NEXT: Offset: 0x27
# BIN-NEXT: - Type: R_WASM_TABLE_NUMBER_LEB
# BIN-NEXT: Index: 5
# BIN-NEXT: Offset: 0x2C
# BIN-NEXT: - Type: R_WASM_TABLE_NUMBER_LEB
# BIN-NEXT: Index: 0
# BIN-NEXT: Offset: 0x37
# BIN-NEXT: - Type: R_WASM_TABLE_NUMBER_LEB
# BIN-NEXT: Index: 0
# BIN-NEXT: Offset: 0x2D
# BIN-NEXT: Offset: 0x44
# BIN-NEXT: - Type: R_WASM_TABLE_NUMBER_LEB
# BIN-NEXT: Index: 0
# BIN-NEXT: Offset: 0x38
# BIN-NEXT: Offset: 0x4F
# BIN-NEXT: - Type: R_WASM_TABLE_NUMBER_LEB
# BIN-NEXT: Index: 0
# BIN-NEXT: Offset: 0x41
# BIN-NEXT: Offset: 0x58
# BIN-NEXT: - Type: R_WASM_TABLE_NUMBER_LEB
# BIN-NEXT: Index: 2
# BIN-NEXT: Offset: 0x51
# BIN-NEXT: Offset: 0x68
# BIN-NEXT: - Type: R_WASM_TABLE_NUMBER_LEB
# BIN-NEXT: Index: 2
# BIN-NEXT: Offset: 0x5A
# BIN-NEXT: Offset: 0x71
# BIN-NEXT: Functions:
# BIN-NEXT: - Index: 0
# BIN-NEXT: Locals: []
# BIN-NEXT: Body: 20002001FC108280808000FC0E828080800083808080000B
# BIN-NEXT: Body: 20002001FC108380808000FC0E8380808000848080800020002001FC108480808000FC0E848080800080808080000B
# BIN-NEXT: - Index: 1
# BIN-NEXT: Locals: []
# BIN-NEXT: Body: 20002580808080000B
# BIN-NEXT: Body: 20002581808080000B
# BIN-NEXT: - Index: 2
# BIN-NEXT: Locals: []
# BIN-NEXT: Body: 200020012680808080000B
# BIN-NEXT: Body: 200020012681808080000B
# BIN-NEXT: - Index: 3
# BIN-NEXT: Locals: []
# BIN-NEXT: Body: 41002580808080002000FC0F808080800020006A0B
# BIN-NEXT: Body: 41002581808080002000FC0F818080800020006A0B
# BIN-NEXT: - Index: 4
# BIN-NEXT: Locals: []
# BIN-NEXT: Body: 200041002582808080002001FC1182808080000B
# BIN-NEXT: Body: 200041002583808080002001FC1183808080000B

# BIN: - Type: CUSTOM
# BIN-NEXT: Name: linking
Expand All @@ -184,20 +214,25 @@ table_fill:
# BIN-NEXT: Kind: TABLE
# BIN-NEXT: Name: foo
# BIN-NEXT: Flags: [ BINDING_LOCAL ]
# BIN-NEXT: Table: 0
# BIN-NEXT: Table: 1
# BIN-NEXT: - Index: 1
# BIN-NEXT: Kind: TABLE
# BIN-NEXT: Name: bar
# BIN-NEXT: Flags: [ BINDING_LOCAL ]
# BIN-NEXT: Table: 1
# BIN-NEXT: Table: 2
# BIN-NEXT: - Index: 2
# BIN-NEXT: Kind: TABLE
# BIN-NEXT: Name: table1
# BIN-NEXT: Flags: [ BINDING_LOCAL ]
# BIN-NEXT: Table: 2
# BIN-NEXT: Table: 3
# BIN-NEXT: - Index: 3
# BIN-NEXT: Kind: TABLE
# BIN-NEXT: Name: table2
# BIN-NEXT: Flags: [ BINDING_LOCAL ]
# BIN-NEXT: Table: 3
# BIN-NEXT: - Index: 4
# BIN-NEXT: Table: 4
# BIN: - Index: 5
# BIN-NEXT: Kind: TABLE
# BIN-NEXT: Name: table3
# BIN-NEXT: Flags: [ UNDEFINED, EXPLICIT_NAME ]
# BIN-NEXT: Table: 0
# BIN-NEXT: - Index: 6