[WebAssembly] Make segment/size/type directives optional in asm
Summary:
These were "boilerplate" that repeated information already present
in .functype and end_function, that needed to be repeated to Please
the particular way our object writing works, and missing them would
generate errors.
Instead, we generate the information for these automatically so the
user can concern itself with writing more canonical wasm functions
that always work as expected.
Reviewers: dschuff, sbc100
Subscribers: jgravelle-google, aheejin, sunfish, llvm-commits
Differential Revision: https://reviews.llvm.org/D57546
llvm-svn: 353067
diff --git a/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp b/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
index 48af89f..a0455cb 100644
--- a/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
+++ b/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
@@ -17,10 +17,12 @@
#include "MCTargetDesc/WebAssemblyTargetStreamer.h"
#include "WebAssembly.h"
#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/MC/MCParser/MCParsedAsmOperand.h"
#include "llvm/MC/MCParser/MCTargetAsmParser.h"
+#include "llvm/MC/MCSectionWasm.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/MCSymbol.h"
@@ -169,6 +171,7 @@
FunctionStart,
FunctionLocals,
Instructions,
+ EndFunction,
} CurrentState = FileStart;
// For ensuring blocks are properly nested.
@@ -186,6 +189,7 @@
// We track this to see if a .functype following a label is the same,
// as this is how we recognize the start of a function.
MCSymbol *LastLabel = nullptr;
+ MCSymbol *LastFunctionLabel = nullptr;
public:
WebAssemblyAsmParser(const MCSubtargetInfo &STI, MCAsmParser &Parser,
@@ -445,6 +449,7 @@
if (pop(BaseName, Block))
return true;
} else if (BaseName == "end_function") {
+ CurrentState = EndFunction;
if (pop(BaseName, Function) || ensureEmptyNestingStack())
return true;
}
@@ -604,6 +609,7 @@
if (ensureEmptyNestingStack())
return true;
CurrentState = FunctionStart;
+ LastFunctionLabel = LastLabel;
push(Function);
}
auto Signature = make_unique<wasm::WasmSignature>();
@@ -666,8 +672,12 @@
*Out.getTargetStreamer());
TOut.emitLocal(SmallVector<wasm::ValType, 0>());
}
- CurrentState = Instructions;
Out.EmitInstruction(Inst, getSTI());
+ if (CurrentState == EndFunction) {
+ onEndOfFunction();
+ } else {
+ CurrentState = Instructions;
+ }
return false;
}
case Match_MissingFeature:
@@ -693,6 +703,30 @@
llvm_unreachable("Implement any new match types added!");
}
+ void doBeforeLabelEmit(MCSymbol *Symbol) override {
+ // Start a new section for the next function automatically, since our
+ // object writer expects each function to have its own section. This way
+ // The user can't forget this "convention".
+ auto SymName = Symbol->getName();
+ if (SymName.startswith(".L"))
+ return; // Local Symbol.
+ auto SecName = ".text." + SymName;
+ auto WS = getContext().getWasmSection(SecName, SectionKind::getText());
+ getStreamer().SwitchSection(WS);
+ }
+
+ void onEndOfFunction() {
+ // Automatically output a .size directive, so it becomes optional for the
+ // user.
+ auto TempSym = getContext().createLinkerPrivateTempSymbol();
+ getStreamer().EmitLabel(TempSym);
+ auto Start = MCSymbolRefExpr::create(LastLabel, getContext());
+ auto End = MCSymbolRefExpr::create(TempSym, getContext());
+ auto Expr =
+ MCBinaryExpr::create(MCBinaryExpr::Sub, End, Start, getContext());
+ getStreamer().emitELFSize(LastFunctionLabel, Expr);
+ }
+
void onEndOfFile() override { ensureEmptyNestingStack(); }
};
} // end anonymous namespace