Iasm and obj lowering for advanced switch lowering.

src/IceCfg.cpp

Index: src/IceCfg.cpp
diff --git a/src/IceCfg.cpp b/src/IceCfg.cpp
index 7e915081700eec8a629c7d3f2fdbc61aba98a43c..3ff367579d6d45d57a92daca8c441f8706f3e467 100644
--- a/src/IceCfg.cpp
+++ b/src/IceCfg.cpp
@@ -529,6 +529,12 @@ void Cfg::doBranchOpt() {
   }
 }
 
+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
@@ -554,6 +560,40 @@ void Cfg::emitTextHeader(const IceString &MangledName, GlobalContext *Ctx,
   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;
@@ -566,10 +606,20 @@ void Cfg::emit() {
   }
   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";
 }
 
@@ -577,8 +627,14 @@ 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.