Subzero: Add Non-SFI support for x86-32.

src/IceTargetLoweringX8632.cpp

Index: src/IceTargetLoweringX8632.cpp
diff --git a/src/IceTargetLoweringX8632.cpp b/src/IceTargetLoweringX8632.cpp
index a09629c477d7f6f4032eeeca09580128c0464a1d..56731f66be9a346bbf4dbf8c6bff09b80aaf2712 100644
--- a/src/IceTargetLoweringX8632.cpp
+++ b/src/IceTargetLoweringX8632.cpp
@@ -99,6 +99,14 @@ template <>
 llvm::SmallBitVector
     TargetX86Base<TargetX8632>::ScratchRegs = llvm::SmallBitVector();
 
+template <>
+FixupKind TargetX86Base<TargetX8632>::PcRelFixup =
+    TargetX86Base<TargetX8632>::Traits::FK_PcRel;
+
+template <>
+FixupKind TargetX86Base<TargetX8632>::AbsFixup =
+    TargetX86Base<TargetX8632>::Traits::FK_Abs;
+
 } // end of namespace X86Internal
 
 //------------------------------------------------------------------------------
@@ -229,7 +237,8 @@ void TargetX8632::lowerCall(const InstCall *Instr) {
       break;
     }
   }
-  Operand *CallTarget = legalize(Instr->getCallTarget());
+  Operand *CallTarget =
+      legalize(Instr->getCallTarget(), Legal_Reg | Legal_Imm | Legal_AddrAbs);
   const bool NeedSandboxing = Ctx->getFlags().getUseSandboxing();
   if (NeedSandboxing) {
     if (llvm::isa<Constant>(CallTarget)) {
@@ -403,6 +412,21 @@ void TargetX8632::addProlog(CfgNode *Node) {
   Context.init(Node);
   Context.setInsertPoint(Context.getCur());
 
+  // If there is a non-deleted InstX86GetIP instruction, we need to move it to

[John, 2016/01/04 21:33:51]

Can you move this block closer to where GetIpInst is used? There are > 100 lines
between here and the next use of this Instruction.

This is also a very good candidate for becoming a helper function.

[Jim Stichnoth, 2016/01/04 23:32:12]

Moved the def and use closer together - with a comment that translation may be
slightly faster if we do the search before adding new prolog instructions.

+  // the point after the stack frame has stabilized but before
+  // register-allocated in-args are copied into their home registers.
+  X86Internal::InstX86GetIP<TargetX8632> *GetIPInst = nullptr;

[John, 2016/01/04 21:33:51]

whenever you add an X86 instruction, add it to the X86Internal::Insts template
struct, then reference it with

Traits::Insts::

instead.

X86Internal should only be referenced in "using" statements, and in .cpp when
instantiating target-specific data.

[Jim Stichnoth, 2016/01/04 23:32:12]

Done.

+  if (Ctx->getFlags().getUseNonsfi()) {
+    for (Inst &Instr : Node->getInsts()) {
+      if (auto *GetIP =
+              llvm::dyn_cast<X86Internal::InstX86GetIP<TargetX8632>>(&Instr)) {
+        if (!Instr.isDeleted())
+          GetIPInst = GetIP;
+        break;
+      }
+    }
+  }
+
   llvm::SmallBitVector CalleeSaves =
       getRegisterSet(RegSet_CalleeSave, RegSet_None);
   RegsUsed = llvm::SmallBitVector(CalleeSaves.size());
@@ -544,6 +568,27 @@ void TargetX8632::addProlog(CfgNode *Node) {
   if (!IsEbpBasedFrame)
     BasicFrameOffset += SpillAreaSizeBytes;
 
+  // Delete any existing InstX86GetIP instruction and reinsert it here.  Also,
+  // insert the call to the helper function and the spill to the stack, to
+  // simplify emission.
+  if (GetIPInst) {
+    GetIPInst->setDeleted();
+    Variable *Dest = GetIPInst->getDest();
+    Variable *CallDest =
+        Dest->hasReg() ? Dest
+                       : getPhysicalRegister(Traits::RegisterSet::Reg_eax);
+    // Call the getIP_<reg> helper.
+    IceString RegName = Traits::getRegName(CallDest->getRegNum());
+    Constant *CallTarget = Ctx->getConstantExternSym(H_getIP_prefix + RegName);
+    Context.insert<Traits::Insts::Call>(CallDest, CallTarget);
+    // Insert a new version of InstX86GetIP.
+    Context.insert<X86Internal::InstX86GetIP<TargetX8632>>(CallDest);
+    // Spill the register to its home stack location if necessary.
+    if (!Dest->hasReg()) {
+      _mov(Dest, CallDest);
+    }
+  }
+
   const VarList &Args = Func->getArgs();
   size_t InArgsSizeBytes = 0;
   unsigned NumXmmArgs = 0;
@@ -684,8 +729,10 @@ void TargetX8632::emitJumpTable(const Cfg *Func,
   if (!BuildDefs::dump())
     return;
   Ostream &Str = Ctx->getStrEmit();
-  IceString MangledName = Ctx->mangleName(Func->getFunctionName());
-  Str << "\t.section\t.rodata." << MangledName
+  const bool UseNonsfi = Ctx->getFlags().getUseNonsfi();
+  const IceString MangledName = Ctx->mangleName(Func->getFunctionName());
+  const IceString Prefix = UseNonsfi ? ".data.rel.ro." : ".rodata.";
+  Str << "\t.section\t" << Prefix << MangledName
       << "$jumptable,\"a\",@progbits\n";
   Str << "\t.align\t" << typeWidthInBytes(getPointerType()) << "\n";
   Str << InstJumpTable::makeName(MangledName, JumpTable->getId()) << ":";
@@ -844,11 +891,12 @@ void TargetDataX8632::lowerConstants() {
 }
 
 void TargetDataX8632::lowerJumpTables() {
+  const bool IsPIC = Ctx->getFlags().getUseNonsfi();
   switch (Ctx->getFlags().getOutFileType()) {
   case FT_Elf: {
     ELFObjectWriter *Writer = Ctx->getObjectWriter();
     for (const JumpTableData &JT : Ctx->getJumpTables())
-      Writer->writeJumpTable(JT, TargetX8632::Traits::RelFixup);
+      Writer->writeJumpTable(JT, TargetX8632::Traits::FK_Abs, IsPIC);
   } break;
   case FT_Asm:
     // Already emitted from Cfg
@@ -857,8 +905,9 @@ void TargetDataX8632::lowerJumpTables() {
     if (!BuildDefs::dump())
       return;
     Ostream &Str = Ctx->getStrEmit();
+    const IceString Prefix = IsPIC ? ".data.rel.ro." : ".rodata.";
     for (const JumpTableData &JT : Ctx->getJumpTables()) {
-      Str << "\t.section\t.rodata." << JT.getFunctionName()
+      Str << "\t.section\t" << Prefix << JT.getFunctionName()
           << "$jumptable,\"a\",@progbits\n";
       Str << "\t.align\t" << typeWidthInBytes(getPointerType()) << "\n";
       Str << InstJumpTable::makeName(JT.getFunctionName(), JT.getId()) << ":";
@@ -874,11 +923,12 @@ void TargetDataX8632::lowerJumpTables() {
 
 void TargetDataX8632::lowerGlobals(const VariableDeclarationList &Vars,
                                    const IceString &SectionSuffix) {
+  const bool IsPIC = Ctx->getFlags().getUseNonsfi();
   switch (Ctx->getFlags().getOutFileType()) {
   case FT_Elf: {
     ELFObjectWriter *Writer = Ctx->getObjectWriter();
-    Writer->writeDataSection(Vars, TargetX8632::Traits::RelFixup,
-                             SectionSuffix);
+    Writer->writeDataSection(Vars, TargetX8632::Traits::FK_Abs, SectionSuffix,
+                             IsPIC);
   } break;
   case FT_Asm:
   case FT_Iasm: {