[WebAssembly] Allow for the creation of user-defined custom sections
This patch adds a way for users to create their own custom sections to
be added to wasm files. At the LLVM IR layer, they are defined through
the "wasm.custom_sections" named metadata. The expected use case for
this is bindings generators such as wasm-bindgen.
Patch by Dan Gohman
Differential Revision: https://reviews.llvm.org/D45297
llvm-svn: 329315
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
index 4f7c68d..e8144ad 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
@@ -31,10 +31,11 @@
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCSectionWasm.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
-#include "llvm/MC/MCSymbolWasm.h"
#include "llvm/MC/MCSymbolELF.h"
+#include "llvm/MC/MCSymbolWasm.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/raw_ostream.h"
@@ -107,6 +108,26 @@
}
}
}
+
+ if (const NamedMDNode *Named = M.getNamedMetadata("wasm.custom_sections")) {
+ for (const Metadata *MD : Named->operands()) {
+ const MDTuple *Tuple = dyn_cast<MDTuple>(MD);
+ if (!Tuple || Tuple->getNumOperands() != 2)
+ continue;
+ const MDString *Name = dyn_cast<MDString>(Tuple->getOperand(0));
+ const MDString *Contents = dyn_cast<MDString>(Tuple->getOperand(1));
+ if (!Name || !Contents)
+ continue;
+
+ OutStreamer->PushSection();
+ std::string SectionName = (".custom_section." + Name->getString()).str();
+ MCSectionWasm *mySection =
+ OutContext.getWasmSection(SectionName, SectionKind::getMetadata());
+ OutStreamer->SwitchSection(mySection);
+ OutStreamer->EmitBytes(Contents->getString());
+ OutStreamer->PopSection();
+ }
+ }
}
void WebAssemblyAsmPrinter::EmitConstantPool() {