[WebAssembly] Assembler/InstPrinter: support call_indirect type index.

A TYPE_INDEX operand (as used by call_indirect) used to be represented
by the InstPrinter as a symbol (e.g. .Ltype_index0@TYPE_INDEX) which
was a bit of a mismatch with the WasmObjectWriter which expects an
unnamed symbol, to receive the signature from and then turn into a
reloc.

There was really no good way to round-trip this information. An earlier
version of this patch tried to attach the signature information using
a .functype, but that ran into trouble when the symbol was re-emitted
without a name. Removing the name was a giant hack also.

The current version changes the assembly syntax to have an inline
signature spec for TYPEINDEX operands that is always unnamed, which
is much more elegant both in syntax and in implementation (as now the
assembler is able to follow the same path as the regular backend)

Reviewers: sbc100, dschuff, aheejin, jgravelle-google, sunfish, tlively

Subscribers: arphaman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64758

llvm-svn: 367590

1 files changed, 31 insertions, 3 deletions

diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyInstPrinter.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyInstPrinter.cpp
index b5d4d369b72..bc63382aa8f 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyInstPrinter.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyInstPrinter.cpp
@@ -15,6 +15,7 @@
 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
 #include "WebAssembly.h"
 #include "WebAssemblyMachineFunctionInfo.h"
+#include "WebAssemblyUtilities.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
@@ -232,7 +233,16 @@ void WebAssemblyInstPrinter::printOperand(const MCInst *MI, unsigned OpNo,
     }
   } else {
     assert(Op.isExpr() && "unknown operand kind in printOperand");
-    Op.getExpr()->print(O, &MAI);
+    // call_indirect instructions have a TYPEINDEX operand that we print
+    // as a signature here, such that the assembler can recover this
+    // information.
+    auto SRE = static_cast<const MCSymbolRefExpr *>(Op.getExpr());
+    if (SRE->getKind() == MCSymbolRefExpr::VK_WASM_TYPEINDEX) {
+      auto &Sym = static_cast<const MCSymbolWasm &>(SRE->getSymbol());
+      O << WebAssembly::signatureToString(Sym.getSignature());
+    } else {
+      Op.getExpr()->print(O, &MAI);
+    }
   }
 }
 
@@ -266,7 +276,7 @@ void WebAssemblyInstPrinter::printWebAssemblySignatureOperand(const MCInst *MI,
 
 // We have various enums representing a subset of these types, use this
 // function to convert any of them to text.
-const char *llvm::WebAssembly::anyTypeToString(unsigned Ty) {
+const char *WebAssembly::anyTypeToString(unsigned Ty) {
   switch (Ty) {
   case wasm::WASM_TYPE_I32:
     return "i32";
@@ -291,6 +301,24 @@ const char *llvm::WebAssembly::anyTypeToString(unsigned Ty) {
   }
 }
 
-const char *llvm::WebAssembly::typeToString(wasm::ValType Ty) {
+const char *WebAssembly::typeToString(wasm::ValType Ty) {
   return anyTypeToString(static_cast<unsigned>(Ty));
 }
+
+std::string WebAssembly::typeListToString(ArrayRef<wasm::ValType> List) {
+  std::string S;
+  for (auto &Ty : List) {
+    if (&Ty != &List[0]) S += ", ";
+    S += WebAssembly::typeToString(Ty);
+  }
+  return S;
+}
+
+std::string WebAssembly::signatureToString(const wasm::WasmSignature *Sig) {
+  std::string S("(");
+  S += typeListToString(Sig->Params);
+  S += ") -> (";
+  S += typeListToString(Sig->Returns);
+  S += ")";
+  return S;
+}