Iasm and obj lowering for advanced switch lowering.

src/IceCfg.cpp

 //===- subzero/src/IceCfg.cpp - Control flow graph implementation ---------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 511 matching lines @@
 }
 
 void Cfg::doBranchOpt() {
   TimerMarker T(TimerStack::TT_doBranchOpt, this);
   for (auto I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
     auto NextNode = I + 1;
     (*I)->doBranchOpt(NextNode == E ? nullptr : *NextNode);
   }
 }
 
+void Cfg::markNodesForSandboxing() {
+  for (const InstJumpTable *JT : JumpTables)
+    for (SizeT I = 0; I < JT->getNumTargets(); ++I)
+      JT->getTarget(I)->setNeedsAlignment();
+}
+
 // ======================== Dump routines ======================== //
 
 // emitTextHeader() is not target-specific (apart from what is
 // abstracted by the Assembler), so it is defined here rather than in
 // the target lowering class.
 void Cfg::emitTextHeader(const IceString &MangledName, GlobalContext *Ctx,
                          const Assembler *Asm) {
   if (!BuildDefs::dump())
     return;
   Ostream &Str = Ctx->getStrEmit();
   Str << "\t.text\n";
   if (Ctx->getFlags().getFunctionSections())
     Str << "\t.section\t.text." << MangledName << ",\"ax\",@progbits\n";
   if (!Asm->getInternal() || Ctx->getFlags().getDisableInternal()) {
     Str << "\t.globl\t" << MangledName << "\n";
     Str << "\t.type\t" << MangledName << ",%function\n";
   }
   Str << "\t" << Asm->getNonExecPadDirective() << " "
       << Asm->getBundleAlignLog2Bytes() << ",0x";
   for (uint8_t I : Asm->getNonExecBundlePadding())
     Str.write_hex(I);
   Str << "\n";
   Str << MangledName << ":\n";
 }
 
+void Cfg::deleteJumpTableInsts() {
+  for (InstJumpTable *JumpTable : JumpTables)
+    JumpTable->setDeleted();
+}
+
+void Cfg::emitJumpTables() {
+  switch (Ctx->getFlags().getOutFileType()) {
+  case FT_Elf:
+  case FT_Iasm: {
+    // The emission needs to be delayed until the after the text section so save
+    // the offsets in the global context.
+    IceString MangledName = Ctx->mangleName(getFunctionName());
+    for (const InstJumpTable *JumpTable : JumpTables) {
+      SizeT NumTargets = JumpTable->getNumTargets();
+      JumpTableData &JT =
+          Ctx->addJumpTable(MangledName, JumpTable->getId(), NumTargets);
+      for (SizeT I = 0; I < NumTargets; ++I) {
+        SizeT Index = JumpTable->getTarget(I)->getIndex();
+        JT.pushTarget(
+            getAssembler()->getOrCreateCfgNodeLabel(Index)->getPosition());
+      }
+    }
+  } break;
+  case FT_Asm: {
+    // Emit the assembly directly so we don't need to hang on to all the names
+    for (const InstJumpTable *JumpTable : JumpTables)
+      getTarget()->emitJumpTable(this, JumpTable);
+  } break;
+  default:
+    llvm::report_fatal_error("Invalid out file type.");
+    break;
+  }
+}
+
 void Cfg::emit() {
   if (!BuildDefs::dump())
     return;
   TimerMarker T(TimerStack::TT_emit, this);
   if (Ctx->getFlags().getDecorateAsm()) {
     renumberInstructions();
     getVMetadata()->init(VMK_Uses);
     liveness(Liveness_Basic);
     dump("After recomputing liveness for -decorate-asm");
   }
   OstreamLocker L(Ctx);
   Ostream &Str = Ctx->getStrEmit();
-  IceString MangledName = getContext()->mangleName(getFunctionName());
-  emitTextHeader(MangledName, Ctx, getAssembler<>());
-  for (CfgNode *Node : Nodes)
+  IceString MangledName = Ctx->mangleName(getFunctionName());
+  const Assembler *Asm = getAssembler<>();
+  const bool NeedSandboxing = Ctx->getFlags().getUseSandboxing();
+
+  emitTextHeader(MangledName, Ctx, Asm);
+  deleteJumpTableInsts();
+  for (CfgNode *Node : Nodes) {
+    if (NeedSandboxing && Node->needsAlignment()) {
+      Str << "\t" << Asm->getNonExecPadDirective() << " "

[jvoung (off chromium), 2015/07/29 21:31:17]

Maybe just rename this from getNonExecPadDirective() -> getAlignDirective()?

For functions we insert NonExec bytes, and need to specify (a) which bytes to
use, and (b) how big an instruction those bytes are (1 byte, 2 byte, 4 byte).
Here, between basic blocks we have executable padding, which is the default from
p2align, so "NonExec" is a bit misleading.

[ascull, 2015/07/29 22:43:04]

Done.

+          << Asm->getBundleAlignLog2Bytes() << "\n";
+    }
     Node->emit(this);
+  }
+  emitJumpTables();
   Str << "\n";
 }
 
 void Cfg::emitIAS() {
   TimerMarker T(TimerStack::TT_emit, this);
   // The emitIAS() routines emit into the internal assembler buffer,
   // so there's no need to lock the streams.
-  for (CfgNode *Node : Nodes)
+  deleteJumpTableInsts();
+  const bool NeedSandboxing = Ctx->getFlags().getUseSandboxing();
+  for (CfgNode *Node : Nodes) {
+    if (NeedSandboxing && Node->needsAlignment())
+      getAssembler()->alignCfgNode();
     Node->emitIAS(this);
+  }
+  emitJumpTables();
 }
 
 // Dumps the IR with an optional introductory message.
 void Cfg::dump(const IceString &Message) {
   if (!BuildDefs::dump())
     return;
   if (!isVerbose())
     return;
   OstreamLocker L(Ctx);
   Ostream &Str = Ctx->getStrDump();
@@ skipping 29 matching lines @@
     }
   }
   // Print each basic block
   for (CfgNode *Node : Nodes)
     Node->dump(this);
   if (isVerbose(IceV_Instructions))
     Str << "}\n";
 }
 
 } // end of namespace Ice