[WebAssembly] Fixed objdump not parsing function headers.

Summary:
objdump was interpreting the function header containing the locals
declaration as instructions. To parse these without injecting target
specific code in objdump, MCDisassembler::onSymbolStart was added to
be implemented by the WebAssembly implemention.

WasmObjectFile now returns a code offset for the "address" of a symbol,
rather than the index. This is also more in-line with what other
targets do.

Also ensured that the AsmParser correctly puts each function
in its own segment to enable this test case.

Reviewers: sbc100, dschuff

Subscribers: jgravelle-google, aheejin, sunfish, rupprecht, llvm-commits

Differential Revision: https://reviews.llvm.org/D56684

llvm-svn: 351460

1 files changed, 42 insertions, 2 deletions

diff --git a/llvm/lib/Target/WebAssembly/Disassembler/WebAssemblyDisassembler.cpp b/llvm/lib/Target/WebAssembly/Disassembler/WebAssemblyDisassembler.cpp
index 6acc9b20eed..ce91a3444fb 100644
--- a/llvm/lib/Target/WebAssembly/Disassembler/WebAssemblyDisassembler.cpp
+++ b/llvm/lib/Target/WebAssembly/Disassembler/WebAssemblyDisassembler.cpp
@@ -15,6 +15,7 @@
 ///
 //===----------------------------------------------------------------------===//
 
+#include "InstPrinter/WebAssemblyInstPrinter.h"
 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCDisassembler/MCDisassembler.h"
@@ -45,6 +46,10 @@ class WebAssemblyDisassembler final : public MCDisassembler {
                               ArrayRef<uint8_t> Bytes, uint64_t Address,
                               raw_ostream &VStream,
                               raw_ostream &CStream) const override;
+  DecodeStatus onSymbolStart(StringRef Name, uint64_t &Size,
+                             ArrayRef<uint8_t> Bytes, uint64_t Address,
+                             raw_ostream &VStream,
+                             raw_ostream &CStream) const override;
 
 public:
   WebAssemblyDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx,
@@ -77,7 +82,7 @@ static int nextByte(ArrayRef<uint8_t> Bytes, uint64_t &Size) {
 }
 
 static bool nextLEB(int64_t &Val, ArrayRef<uint8_t> Bytes, uint64_t &Size,
-                    bool Signed = false) {
+                    bool Signed) {
   unsigned N = 0;
   const char *Error = nullptr;
   Val = Signed ? decodeSLEB128(Bytes.data() + Size, &N,
@@ -116,6 +121,41 @@ bool parseImmediate(MCInst &MI, uint64_t &Size, ArrayRef<uint8_t> Bytes) {
   return true;
 }
 
+MCDisassembler::DecodeStatus WebAssemblyDisassembler::onSymbolStart(
+    StringRef Name, uint64_t &Size, ArrayRef<uint8_t> Bytes, uint64_t Address,
+    raw_ostream &VStream, raw_ostream &CStream) const {
+  Size = 0;
+  if (Address == 0) {
+    // Start of a code section: we're parsing only the function count.
+    int64_t FunctionCount;
+    if (!nextLEB(FunctionCount, Bytes, Size, false))
+      return MCDisassembler::Fail;
+    outs() << "        # " << FunctionCount << " functions in section.";
+  } else {
+    // Parse the start of a single function.
+    int64_t BodySize, LocalEntryCount;
+    if (!nextLEB(BodySize, Bytes, Size, false) ||
+        !nextLEB(LocalEntryCount, Bytes, Size, false))
+      return MCDisassembler::Fail;
+    if (LocalEntryCount) {
+      outs() << "        .local ";
+      for (int64_t I = 0; I < LocalEntryCount; I++) {
+        int64_t Count, Type;
+        if (!nextLEB(Count, Bytes, Size, false) ||
+            !nextLEB(Type, Bytes, Size, false))
+          return MCDisassembler::Fail;
+        for (int64_t J = 0; J < Count; J++) {
+          if (I || J)
+            outs() << ", ";
+          outs() << WebAssembly::anyTypeToString(Type);
+        }
+      }
+    }
+  }
+  outs() << "\n";
+  return MCDisassembler::Success;
+}
+
 MCDisassembler::DecodeStatus WebAssemblyDisassembler::getInstruction(
     MCInst &MI, uint64_t &Size, ArrayRef<uint8_t> Bytes, uint64_t /*Address*/,
     raw_ostream & /*OS*/, raw_ostream &CS) const {
@@ -138,7 +178,7 @@ MCDisassembler::DecodeStatus WebAssemblyDisassembler::getInstruction(
     if (!WasmInst)
       return MCDisassembler::Fail;
     int64_t PrefixedOpc;
-    if (!nextLEB(PrefixedOpc, Bytes, Size))
+    if (!nextLEB(PrefixedOpc, Bytes, Size, false))
       return MCDisassembler::Fail;
     if (PrefixedOpc < 0 || PrefixedOpc >= WebAssemblyInstructionTableSize)
       return MCDisassembler::Fail;