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[WebAssembly] MC: Fix for address taken aliases
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Previously, taking the address for an alias would result in:
 "Symbol not found in table index space"

Increase test coverage for weak aliases.

This code should be more efficient too as it avoids building
the `IsAddressTaken` set.

Differential Revision: https://reviews.llvm.org/D41510

llvm-svn: 321384
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@sbc100
sbc100 committed Dec 22, 2017
1 parent 92365ca commit 6006e09
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Showing 2 changed files with 148 additions and 67 deletions.
69 changes: 30 additions & 39 deletions llvm/lib/MC/WasmObjectWriter.cpp
View file
Expand Up @@ -553,7 +553,7 @@ uint32_t WasmObjectWriter::getRelocationIndexValue(
case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32:
if (!IndirectSymbolIndices.count(RelEntry.Symbol))
report_fatal_error("symbol not found table index space: " +
report_fatal_error("symbol not found in table index space: " +
RelEntry.Symbol->getName());
return IndirectSymbolIndices[RelEntry.Symbol];
case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
Expand All @@ -562,7 +562,7 @@ uint32_t WasmObjectWriter::getRelocationIndexValue(
case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
if (!SymbolIndices.count(RelEntry.Symbol))
report_fatal_error("symbol not found function/global index space: " +
report_fatal_error("symbol not found in function/global index space: " +
RelEntry.Symbol->getName());
return SymbolIndices[RelEntry.Symbol];
case wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB:
Expand Down Expand Up @@ -994,33 +994,10 @@ void WasmObjectWriter::writeObject(MCAssembler &Asm,
SmallVector<WasmExport, 4> Exports;
SmallVector<std::pair<StringRef, uint32_t>, 4> SymbolFlags;
SmallVector<std::pair<uint16_t, uint32_t>, 2> InitFuncs;
SmallPtrSet<const MCSymbolWasm *, 4> IsAddressTaken;
unsigned NumFuncImports = 0;
SmallVector<WasmDataSegment, 4> DataSegments;
uint32_t DataSize = 0;

// Populate the IsAddressTaken set.
for (const WasmRelocationEntry &RelEntry : CodeRelocations) {
switch (RelEntry.Type) {
case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
IsAddressTaken.insert(RelEntry.Symbol);
break;
default:
break;
}
}
for (const WasmRelocationEntry &RelEntry : DataRelocations) {
switch (RelEntry.Type) {
case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32:
case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
IsAddressTaken.insert(RelEntry.Symbol);
break;
default:
break;
}
}

// In the special .global_variables section, we've encoded global
// variables used by the function. Translate them into the Globals
// list.
Expand Down Expand Up @@ -1217,14 +1194,7 @@ void WasmObjectWriter::writeObject(MCAssembler &Asm,
}

DEBUG(dbgs() << " -> function index: " << Index << "\n");

// If needed, prepare the function to be called indirectly.
if (IsAddressTaken.count(&WS) != 0) {
IndirectSymbolIndices[&WS] = TableElems.size();
DEBUG(dbgs() << " -> adding to table: " << TableElems.size() << "\n");
TableElems.push_back(Index);
}
} else {
} else {
if (WS.isTemporary() && !WS.getSize())
continue;

Expand Down Expand Up @@ -1288,7 +1258,6 @@ void WasmObjectWriter::writeObject(MCAssembler &Asm,
uint32_t Index = SymbolIndices.find(ResolvedSym)->second;
DEBUG(dbgs() << " -> index:" << Index << "\n");

//SymbolIndices[&WS] = Index;
WasmExport Export;
Export.FieldName = WS.getName();
Export.Index = Index;
Expand All @@ -1303,12 +1272,34 @@ void WasmObjectWriter::writeObject(MCAssembler &Asm,
SymbolFlags.emplace_back(WS.getName(), wasm::WASM_SYMBOL_BINDING_LOCAL);
}

// Add types for indirect function calls.
for (const WasmRelocationEntry &Fixup : CodeRelocations) {
if (Fixup.Type != wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB)
continue;
{
auto HandleReloc = [&](const WasmRelocationEntry &Rel) {
// Functions referenced by a relocation need to prepared to be called
// indirectly.
const MCSymbolWasm& WS = *Rel.Symbol;
if (WS.isFunction() && IndirectSymbolIndices.count(&WS) == 0) {
switch (Rel.Type) {
case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32:
case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB: {
uint32_t Index = SymbolIndices.find(&WS)->second;
IndirectSymbolIndices[&WS] = TableElems.size();
DEBUG(dbgs() << " -> adding to table: " << TableElems.size() << "\n");
TableElems.push_back(Index);
registerFunctionType(WS);
break;
}
default:
break;
}
}
};

registerFunctionType(*Fixup.Symbol);
for (const WasmRelocationEntry &RelEntry : CodeRelocations)
HandleReloc(RelEntry);
for (const WasmRelocationEntry &RelEntry : DataRelocations)
HandleReloc(RelEntry);
}

// Translate .init_array section contents into start functions.
Expand Down
146 changes: 118 additions & 28 deletions llvm/test/MC/WebAssembly/weak-alias.ll
View file
Expand Up @@ -8,21 +8,41 @@

@bar = global i32 7, align 8
@bar_alias = weak hidden alias i32, i32* @bar
@bar_alias_address = global i32* @bar_alias, align 8

@foo_alias = weak hidden alias i32 (), i32 ()* @foo

@direct_address = global i32()* @foo, align 8
@alias_address = global i32()* @foo_alias, align 8

define hidden i32 @foo() #0 {
entry:
ret i32 0
}

define hidden i32 @call_direct() #0 {
entry:
%call = call i32 @foo()
ret i32 %call
}

define hidden i32 @call_alias() #0 {
entry:
%call = call i32 @foo_alias()
ret i32 %call
}

define hidden i32 @foo() #0 {
define hidden i32 @call_direct_ptr() #0 {
entry:
ret i32 0
%0 = load i32 ()*, i32 ()** @direct_address, align 8
%call = call i32 %0()
ret i32 %call
}

define hidden i32 @call_alias_ptr() #0 {
entry:
%0 = load i32 ()*, i32 ()** @alias_address, align 8
%call = call i32 %0()
ret i32 %call
}

; CHECK: - Type: TYPE
; CHECK-NEXT: Signatures:
Expand All @@ -42,7 +62,7 @@ entry:
; CHECK-NEXT: Table:
; CHECK-NEXT: ElemType: ANYFUNC
; CHECK-NEXT: Limits:
; CHECK-NEXT: Initial: 0x00000000
; CHECK-NEXT: Initial: 0x00000002
; CHECK-NEXT: - Module: env
; CHECK-NEXT: Field: foo_alias
; CHECK-NEXT: Kind: FUNCTION
Expand All @@ -53,54 +73,101 @@ entry:
; CHECK-NEXT: GlobalType: I32
; CHECK-NEXT: GlobalMutable: false
; CHECK-NEXT: - Type: FUNCTION
; CHECK-NEXT: FunctionTypes: [ 0, 0 ]
; CHECK-NEXT: FunctionTypes: [ 0, 0, 0, 0, 0 ]
; CHECK-NEXT: - Type: GLOBAL
; CHECK-NEXT: Globals:
; CHECK-NEXT: - Type: I32
; CHECK-NEXT: Mutable: false
; CHECK-NEXT: InitExpr:
; CHECK-NEXT: Opcode: I32_CONST
; CHECK-NEXT: Value: 0
; CHECK-NEXT: Value: 8
; CHECK-NEXT: - Type: I32
; CHECK-NEXT: Mutable: false
; CHECK-NEXT: InitExpr:
; CHECK-NEXT: Opcode: I32_CONST
; CHECK-NEXT: Value: 8
; CHECK-NEXT: Value: 16
; CHECK-NEXT: - Type: I32
; CHECK-NEXT: Mutable: false
; CHECK-NEXT: InitExpr:
; CHECK-NEXT: Opcode: I32_CONST
; CHECK-NEXT: Value: 0
; CHECK-NEXT: - Type: EXPORT
; CHECK-NEXT: Exports:
; CHECK-NEXT: - Name: call_alias
; CHECK-NEXT: - Name: foo
; CHECK-NEXT: Kind: FUNCTION
; CHECK-NEXT: Index: 1
; CHECK-NEXT: - Name: foo
; CHECK-NEXT: - Name: call_direct
; CHECK-NEXT: Kind: FUNCTION
; CHECK-NEXT: Index: 2
; CHECK-NEXT: - Name: bar
; CHECK-NEXT: - Name: call_alias
; CHECK-NEXT: Kind: FUNCTION
; CHECK-NEXT: Index: 3
; CHECK-NEXT: - Name: call_direct_ptr
; CHECK-NEXT: Kind: FUNCTION
; CHECK-NEXT: Index: 4
; CHECK-NEXT: - Name: direct_address
; CHECK-NEXT: Kind: GLOBAL
; CHECK-NEXT: Index: 1
; CHECK-NEXT: - Name: bar_alias_address
; CHECK-NEXT: - Name: call_alias_ptr
; CHECK-NEXT: Kind: FUNCTION
; CHECK-NEXT: Index: 5
; CHECK-NEXT: - Name: alias_address
; CHECK-NEXT: Kind: GLOBAL
; CHECK-NEXT: Index: 2
; CHECK-NEXT: - Name: bar
; CHECK-NEXT: Kind: GLOBAL
; CHECK-NEXT: Index: 3
; CHECK-NEXT: - Name: foo_alias
; CHECK-NEXT: Kind: FUNCTION
; CHECK-NEXT: Index: 2
; CHECK-NEXT: Index: 1
; CHECK-NEXT: - Name: bar_alias
; CHECK-NEXT: Kind: GLOBAL
; CHECK-NEXT: Index: 1
; CHECK-NEXT: Index: 3
; CHECK-NEXT: - Type: ELEM
; CHECK-NEXT: Segments:
; CHECK-NEXT: - Offset:
; CHECK-NEXT: Opcode: I32_CONST
; CHECK-NEXT: Value: 0
; CHECK-NEXT: Functions: [ 1, 0 ]
; CHECK-NEXT: - Type: CODE
; CHECK-NEXT: Relocations:
; CHECK-NEXT: - Type: R_WEBASSEMBLY_FUNCTION_INDEX_LEB
; CHECK-NEXT: Index: 1
; CHECK-NEXT: Offset: 0x00000009
; CHECK-NEXT: - Type: R_WEBASSEMBLY_FUNCTION_INDEX_LEB
; CHECK-NEXT: Index: 0
; CHECK-NEXT: Offset: 0x00000012
; CHECK-NEXT: - Type: R_WEBASSEMBLY_MEMORY_ADDR_LEB
; CHECK-NEXT: Index: 1
; CHECK-NEXT: Offset: 0x0000001E
; CHECK-NEXT: - Type: R_WEBASSEMBLY_TYPE_INDEX_LEB
; CHECK-NEXT: Index: 0
; CHECK-NEXT: Offset: 0x00000004
; CHECK-NEXT: Offset: 0x00000024
; CHECK-NEXT: - Type: R_WEBASSEMBLY_MEMORY_ADDR_LEB
; CHECK-NEXT: Index: 2
; CHECK-NEXT: Offset: 0x00000031
; CHECK-NEXT: - Type: R_WEBASSEMBLY_TYPE_INDEX_LEB
; CHECK-NEXT: Index: 0
; CHECK-NEXT: Offset: 0x00000037
; CHECK-NEXT: Functions:
; CHECK-NEXT: - Locals:
; CHECK-NEXT: Body: 41000B
; CHECK-NEXT: - Locals:
; CHECK-NEXT: Body: 1081808080000B
; CHECK-NEXT: - Locals:
; CHECK-NEXT: Body: 1080808080000B
; CHECK-NEXT: - Locals:
; CHECK-NEXT: Body: 41000B
; CHECK-NEXT: Body: 410028028880808000118080808000000B
; CHECK-NEXT: - Locals:
; CHECK-NEXT: Body: 410028029080808000118080808000000B
; CHECK-NEXT: - Type: DATA
; CHECK-NEXT: Relocations:
; CHECK-NEXT: - Type: R_WEBASSEMBLY_MEMORY_ADDR_I32
; CHECK-NEXT: - Type: R_WEBASSEMBLY_TABLE_INDEX_I32
; CHECK-NEXT: Index: 0
; CHECK-NEXT: Offset: 0x0000000F
; CHECK-NEXT: - Type: R_WEBASSEMBLY_TABLE_INDEX_I32
; CHECK-NEXT: Index: 1
; CHECK-NEXT: Offset: 0x00000018
; CHECK-NEXT: Segments:
; CHECK-NEXT: - SectionOffset: 6
; CHECK-NEXT: MemoryIndex: 0
Expand All @@ -121,39 +188,62 @@ entry:
; CHECK-NEXT: - Index: 0
; CHECK-NEXT: Name: foo_alias
; CHECK-NEXT: - Index: 1
; CHECK-NEXT: Name: call_alias
; CHECK-NEXT: - Index: 2
; CHECK-NEXT: Name: foo
; CHECK-NEXT: - Index: 2
; CHECK-NEXT: Name: call_direct
; CHECK-NEXT: - Index: 3
; CHECK-NEXT: Name: call_alias
; CHECK-NEXT: - Index: 4
; CHECK-NEXT: Name: call_direct_ptr
; CHECK-NEXT: - Index: 5
; CHECK-NEXT: Name: call_alias_ptr
; CHECK-NEXT: - Type: CUSTOM
; CHECK-NEXT: Name: linking
; CHECK-NEXT: DataSize: 12
; CHECK-NEXT: DataSize: 20
; CHECK-NEXT: SymbolInfo:
; CHECK-NEXT: - Name: foo_alias
; CHECK-NEXT: Flags: [ BINDING_WEAK, VISIBILITY_HIDDEN ]
; CHECK-NEXT: - Name: bar_alias
; CHECK-NEXT: Flags: [ BINDING_WEAK, VISIBILITY_HIDDEN ]
; CHECK-NEXT: - Name: foo
; CHECK-NEXT: Flags: [ VISIBILITY_HIDDEN ]
; CHECK-NEXT: - Name: call_direct
; CHECK-NEXT: Flags: [ VISIBILITY_HIDDEN ]
; CHECK-NEXT: - Name: call_alias
; CHECK-NEXT: Flags: [ VISIBILITY_HIDDEN ]
; CHECK-NEXT: - Name: foo
; CHECK-NEXT: - Name: call_direct_ptr
; CHECK-NEXT: Flags: [ VISIBILITY_HIDDEN ]
; CHECK-NEXT: - Name: call_alias_ptr
; CHECK-NEXT: Flags: [ VISIBILITY_HIDDEN ]
; CHECK-NEXT: SegmentInfo:
; CHECK-NEXT: - Index: 0
; CHECK-NEXT: Name: .data.bar
; CHECK-NEXT: Alignment: 8
; CHECK-NEXT: Flags: [ ]
; CHECK-NEXT: - Index: 1
; CHECK-NEXT: Name: .data.bar_alias_address
; CHECK-NEXT: Name: .data.direct_address
; CHECK-NEXT: Alignment: 8
; CHECK-NEXT: Flags: [ ]
; CHECK-NEXT: - Index: 2
; CHECK-NEXT: Name: .data.alias_address
; CHECK-NEXT: Alignment: 8
; CHECK-NEXT: Flags: [ ]
; CHECK-NEXT: ...

; CHECK-SYMS: SYMBOL TABLE:
; CHECK-SYMS-NEXT: 00000000 g F name foo_alias
; CHECK-SYMS-NEXT: 00000001 g F name call_alias
; CHECK-SYMS-NEXT: 00000002 g F name foo
; CHECK-SYMS-NEXT: 00000002 gw F EXPORT .hidden foo_alias
; CHECK-SYMS-NEXT: 00000001 g F name foo
; CHECK-SYMS-NEXT: 00000002 g F name call_direct
; CHECK-SYMS-NEXT: 00000003 g F name call_alias
; CHECK-SYMS-NEXT: 00000004 g F name call_direct_ptr
; CHECK-SYMS-NEXT: 00000005 g F name call_alias_ptr
; CHECK-SYMS-NEXT: 00000001 gw F EXPORT .hidden foo_alias
; CHECK-SYMS-NEXT: 00000000 gw EXPORT .hidden bar_alias
; CHECK-SYMS-NEXT: 00000001 g F EXPORT .hidden call_alias
; CHECK-SYMS-NEXT: 00000002 g F EXPORT .hidden foo
; CHECK-SYMS-NEXT: 00000001 g F EXPORT .hidden foo
; CHECK-SYMS-NEXT: 00000002 g F EXPORT .hidden call_direct
; CHECK-SYMS-NEXT: 00000003 g F EXPORT .hidden call_alias
; CHECK-SYMS-NEXT: 00000004 g F EXPORT .hidden call_direct_ptr
; CHECK-SYMS-NEXT: 00000008 g EXPORT direct_address
; CHECK-SYMS-NEXT: 00000005 g F EXPORT .hidden call_alias_ptr
; CHECK-SYMS-NEXT: 00000010 g EXPORT alias_address
; CHECK-SYMS-NEXT: 00000000 g EXPORT bar
; CHECK-SYMS-NEXT: 00000008 g EXPORT bar_alias_address

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