[WebAssembly] MC: Create wasm data segments based on MCSections
This means that we can honor -fdata-sections rather than
always creating a segment for each symbol.
It also allows for a followup change to add .init_array and friends.
Differential Revision: https://reviews.llvm.org/D37876
llvm-svn: 313395
diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index f601c14..7ed20d32 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -163,7 +163,8 @@
void print(raw_ostream &Out) const {
Out << "Off=" << Offset << ", Sym=" << *Symbol << ", Addend=" << Addend
- << ", Type=" << Type << ", FixupSection=" << FixupSection;
+ << ", Type=" << Type
+ << ", FixupSection=" << FixupSection->getSectionName();
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
@@ -495,6 +496,39 @@
return Value;
}
+static void addData(SmallVectorImpl<char> &DataBytes,
+ MCSectionWasm &DataSection, uint32_t &DataAlignment) {
+ DataBytes.resize(alignTo(DataBytes.size(), DataSection.getAlignment()));
+ DataAlignment = std::max(DataAlignment, DataSection.getAlignment());
+ DEBUG(errs() << "addData: " << DataSection.getSectionName() << "\n");
+
+ for (const MCFragment &Frag : DataSection) {
+ if (Frag.hasInstructions())
+ report_fatal_error("only data supported in data sections");
+
+ if (auto *Align = dyn_cast<MCAlignFragment>(&Frag)) {
+ if (Align->getValueSize() != 1)
+ report_fatal_error("only byte values supported for alignment");
+ // If nops are requested, use zeros, as this is the data section.
+ uint8_t Value = Align->hasEmitNops() ? 0 : Align->getValue();
+ uint64_t Size = std::min<uint64_t>(alignTo(DataBytes.size(),
+ Align->getAlignment()),
+ DataBytes.size() +
+ Align->getMaxBytesToEmit());
+ DataBytes.resize(Size, Value);
+ } else if (auto *Fill = dyn_cast<MCFillFragment>(&Frag)) {
+ DataBytes.insert(DataBytes.end(), Fill->getSize(), Fill->getValue());
+ } else {
+ const auto &DataFrag = cast<MCDataFragment>(Frag);
+ const SmallVectorImpl<char> &Contents = DataFrag.getContents();
+
+ DataBytes.insert(DataBytes.end(), Contents.begin(), Contents.end());
+ }
+ }
+
+ DEBUG(dbgs() << "addData -> " << DataBytes.size() << "\n");
+}
+
uint32_t WasmObjectWriter::getRelocationIndexValue(
const WasmRelocationEntry &RelEntry) {
switch (RelEntry.Type) {
@@ -773,9 +807,7 @@
report_fatal_error(".size expression must be evaluatable");
encodeULEB128(Size, getStream());
-
FuncSection.setSectionOffset(getStream().tell() - Section.ContentsOffset);
-
Asm.writeSectionData(&FuncSection, Layout);
}
@@ -1016,7 +1048,7 @@
// In the special .global_variables section, we've encoded global
// variables used by the function. Translate them into the Globals
// list.
- MCSectionWasm *GlobalVars = Ctx.getWasmSection(".global_variables", 0, 0);
+ MCSectionWasm *GlobalVars = Ctx.getWasmSection(".global_variables", wasm::WASM_SEC_DATA);
if (!GlobalVars->getFragmentList().empty()) {
if (GlobalVars->getFragmentList().size() != 1)
report_fatal_error("only one .global_variables fragment supported");
@@ -1072,7 +1104,7 @@
// In the special .stack_pointer section, we've encoded the stack pointer
// index.
- MCSectionWasm *StackPtr = Ctx.getWasmSection(".stack_pointer", 0, 0);
+ MCSectionWasm *StackPtr = Ctx.getWasmSection(".stack_pointer", wasm::WASM_SEC_DATA);
if (!StackPtr->getFragmentList().empty()) {
if (StackPtr->getFragmentList().size() != 1)
report_fatal_error("only one .stack_pointer fragment supported");
@@ -1089,6 +1121,21 @@
StackPointerGlobal = NumGlobalImports + *(const int32_t *)Contents.data();
}
+ for (MCSection &Sec : Asm) {
+ auto &Section = static_cast<MCSectionWasm &>(Sec);
+ if (Section.getType() != wasm::WASM_SEC_DATA)
+ continue;
+
+ DataSize = alignTo(DataSize, Section.getAlignment());
+ DataSegments.emplace_back();
+ WasmDataSegment &Segment = DataSegments.back();
+ Segment.Offset = DataSize;
+ Segment.Section = &Section;
+ addData(Segment.Data, Section, DataAlignment);
+ DataSize += Segment.Data.size();
+ Section.setMemoryOffset(Segment.Offset);
+ }
+
// Handle regular defined and undefined symbols.
for (const MCSymbol &S : Asm.symbols()) {
// Ignore unnamed temporary symbols, which aren't ever exported, imported,
@@ -1151,9 +1198,6 @@
if (!WS.isDefined(/*SetUsed=*/false))
continue;
- if (WS.getOffset() != 0)
- report_fatal_error("data sections must contain one variable each: " +
- WS.getName());
if (!WS.getSize())
report_fatal_error("data symbols must have a size set with .size: " +
WS.getName());
@@ -1162,58 +1206,20 @@
if (!WS.getSize()->evaluateAsAbsolute(Size, Layout))
report_fatal_error(".size expression must be evaluatable");
- auto &DataSection = static_cast<MCSectionWasm &>(WS.getSection());
-
- if (uint64_t(Size) != Layout.getSectionFileSize(&DataSection))
- report_fatal_error("data sections must contain at most one variable");
-
- DataAlignment = std::max(DataAlignment, DataSection.getAlignment());
-
- DataSegments.emplace_back();
- WasmDataSegment &Segment = DataSegments.back();
-
- DataSize = alignTo(DataSize, DataSection.getAlignment());
- Segment.Offset = DataSize;
- Segment.Section = &DataSection;
-
// For each global, prepare a corresponding wasm global holding its
// address. For externals these will also be named exports.
Index = NumGlobalImports + Globals.size();
+ auto &DataSection = static_cast<MCSectionWasm &>(WS.getSection());
WasmGlobal Global;
Global.Type = PtrType;
Global.IsMutable = false;
Global.HasImport = false;
- Global.InitialValue = DataSize;
+ Global.InitialValue = DataSection.getMemoryOffset() + Layout.getSymbolOffset(WS);
Global.ImportIndex = 0;
SymbolIndices[&WS] = Index;
DEBUG(dbgs() << " -> global index: " << Index << "\n");
Globals.push_back(Global);
-
- for (const MCFragment &Frag : DataSection) {
- if (Frag.hasInstructions())
- report_fatal_error("only data supported in data sections");
-
- if (auto *Align = dyn_cast<MCAlignFragment>(&Frag)) {
- if (Align->getValueSize() != 1)
- report_fatal_error("only byte values supported for alignment");
- // If nops are requested, use zeros, as this is the data section.
- uint8_t Value = Align->hasEmitNops() ? 0 : Align->getValue();
- uint64_t Size = std::min<uint64_t>(
- alignTo(Segment.Data.size(), Align->getAlignment()),
- Segment.Data.size() + Align->getMaxBytesToEmit());
- Segment.Data.resize(Size, Value);
- } else if (auto *Fill = dyn_cast<MCFillFragment>(&Frag)) {
- Segment.Data.insert(Segment.Data.end(), Fill->getSize(), Fill->getValue());
- } else {
- const auto &DataFrag = cast<MCDataFragment>(Frag);
- const SmallVectorImpl<char> &Contents = DataFrag.getContents();
-
- Segment.Data.insert(Segment.Data.end(), Contents.begin(),
- Contents.end());
- }
- }
- DataSize += Segment.Data.size();
}
// If the symbol is visible outside this translation unit, export it.