PNaCl wire format: Remove magic number and hash from encoding of 'switch'

The magic number is no longer needed now that the reader for the old
switch representation has been removed (in
https://codereview.chromium.org/17764003), so we can remove this
baggage.

Also add a missing record size check to the reader.

BUG=https://code.google.com/p/nativeclient/issues/detail?id=3507
TEST=hello_world.pexe includes a switch statement; also PNaCl toolchain trybots

Review URL: https://codereview.chromium.org/17777005

2 files changed, 46 insertions, 55 deletions

diff --git a/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.cpp b/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.cpp
index 0fe72704e0..57dcea8953 100644
--- a/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.cpp
+++ b/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.cpp
@@ -2128,63 +2128,57 @@ bool NaClBitcodeReader::ParseFunctionBody(Function *F) {
       break;
     }
     case naclbitc::FUNC_CODE_INST_SWITCH: { // SWITCH: [opty, op0, op1, ...]
-      // Check magic
-      if ((Record[0] >> 16) == SWITCH_INST_MAGIC) {
-        // New SwitchInst format with case ranges.
-
-        Type *OpTy = getTypeByID(Record[1]);
-        unsigned ValueBitWidth = cast<IntegerType>(OpTy)->getBitWidth();
-
-        Value *Cond = getValue(Record, 2, NextValueNo, OpTy);
-        BasicBlock *Default = getBasicBlock(Record[3]);
-        if (OpTy == 0 || Cond == 0 || Default == 0)
-          return Error("Invalid SWITCH record");
-
-        unsigned NumCases = Record[4];
-
-        SwitchInst *SI = SwitchInst::Create(Cond, Default, NumCases);
-        InstructionList.push_back(SI);
-
-        unsigned CurIdx = 5;
-        for (unsigned i = 0; i != NumCases; ++i) {
-          IntegersSubsetToBB CaseBuilder;
-          unsigned NumItems = Record[CurIdx++];
-          for (unsigned ci = 0; ci != NumItems; ++ci) {
-            bool isSingleNumber = Record[CurIdx++];
-
-            APInt Low;
-            unsigned ActiveWords = 1;
+      // New SwitchInst format with case ranges.
+      if (Record.size() < 4)
+        return Error("Invalid SWITCH record");
+      Type *OpTy = getTypeByID(Record[0]);
+      unsigned ValueBitWidth = cast<IntegerType>(OpTy)->getBitWidth();
+
+      Value *Cond = getValue(Record, 1, NextValueNo, OpTy);
+      BasicBlock *Default = getBasicBlock(Record[2]);
+      if (OpTy == 0 || Cond == 0 || Default == 0)
+        return Error("Invalid SWITCH record");
+
+      unsigned NumCases = Record[3];
+
+      SwitchInst *SI = SwitchInst::Create(Cond, Default, NumCases);
+      InstructionList.push_back(SI);
+
+      unsigned CurIdx = 4;
+      for (unsigned i = 0; i != NumCases; ++i) {
+        IntegersSubsetToBB CaseBuilder;
+        unsigned NumItems = Record[CurIdx++];
+        for (unsigned ci = 0; ci != NumItems; ++ci) {
+          bool isSingleNumber = Record[CurIdx++];
+
+          APInt Low;
+          unsigned ActiveWords = 1;
+          if (ValueBitWidth > 64)
+            ActiveWords = Record[CurIdx++];
+          Low = ReadWideAPInt(makeArrayRef(&Record[CurIdx], ActiveWords),
+                              ValueBitWidth);
+          CurIdx += ActiveWords;
+
+          if (!isSingleNumber) {
+            ActiveWords = 1;
             if (ValueBitWidth > 64)
               ActiveWords = Record[CurIdx++];
-            Low = ReadWideAPInt(makeArrayRef(&Record[CurIdx], ActiveWords),
-                                ValueBitWidth);
-            CurIdx += ActiveWords;
+            APInt High =
+                ReadWideAPInt(makeArrayRef(&Record[CurIdx], ActiveWords),
+                              ValueBitWidth);
 
-            if (!isSingleNumber) {
-              ActiveWords = 1;
-              if (ValueBitWidth > 64)
-                ActiveWords = Record[CurIdx++];
-              APInt High =
-                  ReadWideAPInt(makeArrayRef(&Record[CurIdx], ActiveWords),
-                                ValueBitWidth);
-
-              CaseBuilder.add(IntItem::fromType(OpTy, Low),
-                              IntItem::fromType(OpTy, High));
-              CurIdx += ActiveWords;
-            } else
-              CaseBuilder.add(IntItem::fromType(OpTy, Low));
-          }
-          BasicBlock *DestBB = getBasicBlock(Record[CurIdx++]);
-          IntegersSubset Case = CaseBuilder.getCase();
-          SI->addCase(Case, DestBB);
+            CaseBuilder.add(IntItem::fromType(OpTy, Low),
+                            IntItem::fromType(OpTy, High));
+            CurIdx += ActiveWords;
+          } else
+            CaseBuilder.add(IntItem::fromType(OpTy, Low));
         }
-        uint16_t Hash = SI->hash();
-        if (Hash != (Record[0] & 0xFFFF))
-          return Error("Invalid SWITCH record");
-        I = SI;
-        break;
+        BasicBlock *DestBB = getBasicBlock(Record[CurIdx++]);
+        IntegersSubset Case = CaseBuilder.getCase();
+        SI->addCase(Case, DestBB);
       }
-      return Error("Old SwitchInst representation not supported");
+      I = SI;
+      break;
     }
     case naclbitc::FUNC_CODE_INST_INDIRECTBR: { // INDIRECTBR: [opty, op0, op1, ...]
       if (Record.size() < 2)
diff --git a/lib/Bitcode/NaCl/Writer/NaClBitcodeWriter.cpp b/lib/Bitcode/NaCl/Writer/NaClBitcodeWriter.cpp
index 7afcf666dc..b41b3c83c6 100644
--- a/lib/Bitcode/NaCl/Writer/NaClBitcodeWriter.cpp
+++ b/lib/Bitcode/NaCl/Writer/NaClBitcodeWriter.cpp
@@ -1252,9 +1252,6 @@ static void WriteInstruction(const Instruction &I, unsigned InstID,
       Code = naclbitc::FUNC_CODE_INST_SWITCH;
       const SwitchInst &SI = cast<SwitchInst>(I);
 
-      uint32_t SwitchRecordHeader = SI.hash() | (SWITCH_INST_MAGIC << 16);
-      Vals64.push_back(SwitchRecordHeader);
-
       Vals64.push_back(VE.getTypeID(SI.getCondition()->getType()));
       pushValue64(SI.getCondition(), InstID, Vals64, VE);
       Vals64.push_back(VE.getValueID(SI.getDefaultDest()));