Fix a bug that would cause subzero to fail when --threads=0.

src/IceTargetLowering.cpp

 //===- subzero/src/IceTargetLowering.cpp - Basic lowering implementation --===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the skeleton of the TargetLowering class,
 // specifically invoking the appropriate lowering method for a given
 // instruction kind and driving global register allocation.  It also
 // implements the non-deleted instruction iteration in
 // LoweringContext.
 //
 //===----------------------------------------------------------------------===//
 
+#include <sstream>

[Jim Stichnoth, 2015/06/16 17:03:25]

http://llvm.org/docs/CodingStandards.html#use-raw-ostream

See existing uses of llvm::raw_string_ostream .

[John, 2015/06/16 17:30:55]

no longer relevant here, but Done for IceELFObjectWriter.

+
 #include "IceAssemblerARM32.h"
 #include "IceAssemblerX8632.h"
 #include "assembler_mips32.h"
 #include "IceCfg.h" // setError()
 #include "IceCfgNode.h"
 #include "IceGlobalInits.h"
 #include "IceOperand.h"
 #include "IceRegAlloc.h"
 #include "IceTargetLowering.h"
 #include "IceTargetLoweringARM32.h"
@@ skipping 411 matching lines @@
 #define SUBZERO_TARGET(X)                                                      \
   if (Target == Target_##X)                                                    \
     return TargetData##X::create(Ctx);
 #include "llvm/Config/SZTargets.def"
 
   llvm::report_fatal_error("Unsupported target data lowering");
 }
 
 TargetDataLowering::~TargetDataLowering() {}
 
-void TargetDataLowering::emitGlobal(const VariableDeclaration &Var) {
+namespace {
+
+IceString dataSectionSuffix(const IceString &SectionSuffix,

[Jim Stichnoth, 2015/06/16 17:03:24]

I realize that -fdata-sections hasn't been implemented yet, but if it does get
implemented, this suffix mechanism will make Subzero's data section names
incompatible with llc's data section names, which will affect bisection
debugging.

Would it make sense to print a warning if the user tries to use -fdata-sections
and -enable-block-profile at the same time?

[John, 2015/06/16 17:30:55]

Well, with -fdata-sections we don't need the SectionSuffix (each profile
variable will live in its on section.) I modified the logic here so that, with
-fdata-sections SectionSuffix is simply ignored.

+                            const IceString &MangledVarName,
+                            const bool DataSections) {
+  if (SectionSuffix.empty() && !DataSections) {
+    // Early optimizing the simple case. If no suffix is needed then we should
+    // avoid constructing the ostringstream below.
+    return "";
+  }
+
+  std::ostringstream MangledName;
+
+  if (!SectionSuffix.empty()) {
+    MangledName << "." << SectionSuffix;
+  }
+
+  if (DataSections) {
+    MangledName << "." << MangledVarName;
+  }
+
+  return MangledName.str();
+}
+
+} // end of anonymous namespace
+
+void TargetDataLowering::emitGlobal(const VariableDeclaration &Var,
+                                    const IceString &SectionSuffix) {
   if (!ALLOW_DUMP)
     return;
 
   // If external and not initialized, this must be a cross test.
   // Don't generate a declaration for such cases.
-  bool IsExternal = Var.isExternal() || Ctx->getFlags().getDisableInternal();
+  const bool IsExternal =
+      Var.isExternal() || Ctx->getFlags().getDisableInternal();
   if (IsExternal && !Var.hasInitializer())
     return;
 
   Ostream &Str = Ctx->getStrEmit();
-  const VariableDeclaration::InitializerListType &Initializers =
-      Var.getInitializers();
-  bool HasNonzeroInitializer = Var.hasNonzeroInitializer();
-  bool IsConstant = Var.getIsConstant();
-  uint32_t Align = Var.getAlignment();
-  SizeT Size = Var.getNumBytes();
-  IceString MangledName = Var.mangleName(Ctx);
-  IceString SectionSuffix = "";
-  if (Ctx->getFlags().getDataSections())
-    SectionSuffix = "." + MangledName;
+  const bool HasNonzeroInitializer = Var.hasNonzeroInitializer();
+  const bool IsConstant = Var.getIsConstant();
+  const SizeT Size = Var.getNumBytes();
+  const IceString MangledName = Var.mangleName(Ctx);
 
   Str << "\t.type\t" << MangledName << ",%object\n";
 
+  const bool UseDataSections = Ctx->getFlags().getDataSections();
+  const IceString Suffix =
+      dataSectionSuffix(SectionSuffix, MangledName, UseDataSections);
   if (IsConstant)
-    Str << "\t.section\t.rodata" << SectionSuffix << ",\"a\",%progbits\n";
+    Str << "\t.section\t.rodata" << Suffix << ",\"a\",%progbits\n";
   else if (HasNonzeroInitializer)
-    Str << "\t.section\t.data" << SectionSuffix << ",\"aw\",%progbits\n";
+    Str << "\t.section\t.data" << Suffix << ",\"aw\",%progbits\n";
   else
-    Str << "\t.section\t.bss" << SectionSuffix << ",\"aw\",%nobits\n";
+    Str << "\t.section\t.bss" << Suffix << ",\"aw\",%nobits\n";
 
   if (IsExternal)
     Str << "\t.globl\t" << MangledName << "\n";
 
+  const uint32_t Align = Var.getAlignment();
   if (Align > 1) {
     assert(llvm::isPowerOf2_32(Align));
     // Use the .p2align directive, since the .align N directive can either
     // interpret N as bytes, or power of 2 bytes, depending on the target.
     Str << "\t.p2align\t" << llvm::Log2_32(Align) << "\n";
   }
 
   Str << MangledName << ":\n";
 
   if (HasNonzeroInitializer) {
-    for (VariableDeclaration::Initializer *Init : Initializers) {
+    for (VariableDeclaration::Initializer *Init : Var.getInitializers()) {
       switch (Init->getKind()) {
       case VariableDeclaration::Initializer::DataInitializerKind: {
-        const auto Data = llvm::cast<VariableDeclaration::DataInitializer>(Init)
-                              ->getContents();
+        const auto &Data = llvm::cast<VariableDeclaration::DataInitializer>(
+                               Init)->getContents();
         for (SizeT i = 0; i < Init->getNumBytes(); ++i) {
           Str << "\t.byte\t" << (((unsigned)Data[i]) & 0xff) << "\n";
         }
         break;
       }
       case VariableDeclaration::Initializer::ZeroInitializerKind:
         Str << "\t.zero\t" << Init->getNumBytes() << "\n";
         break;
       case VariableDeclaration::Initializer::RelocInitializerKind: {
-        const auto Reloc =
+        const auto *Reloc =
             llvm::cast<VariableDeclaration::RelocInitializer>(Init);
         Str << "\t" << getEmit32Directive() << "\t";
         Str << Reloc->getDeclaration()->mangleName(Ctx);
         if (RelocOffsetT Offset = Reloc->getOffset()) {
           if (Offset >= 0 || (Offset == INT32_MIN))
             Str << " + " << Offset;
           else
             Str << " - " << -Offset;
         }
         Str << "\n";
         break;
       }
       }
     }
-  } else
+  } else {
     // NOTE: for non-constant zero initializers, this is BSS (no bits),
     // so an ELF writer would not write to the file, and only track
     // virtual offsets, but the .s writer still needs this .zero and
     // cannot simply use the .size to advance offsets.
     Str << "\t.zero\t" << Size << "\n";
+  }
 
   Str << "\t.size\t" << MangledName << ", " << Size << "\n";
 }
 
 std::unique_ptr<TargetHeaderLowering>
 TargetHeaderLowering::createLowering(GlobalContext *Ctx) {
   TargetArch Target = Ctx->getFlags().getTargetArch();
 #define SUBZERO_TARGET(X)                                                      \
   if (Target == Target_##X)                                                    \
     return TargetHeader##X::create(Ctx);
 #include "llvm/Config/SZTargets.def"
 
   llvm::report_fatal_error("Unsupported target header lowering");
 }
 
 TargetHeaderLowering::~TargetHeaderLowering() {}
 
 } // end of namespace Ice