reintroduce support for Mips "small" section handling. This is

implemented somewhat differently than before, but it should have
the same functionality and the previous testcase passes again.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78900 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Mips/CMakeLists.txt

@@ -19,6 +19,7 @@ add_llvm_target(MipsCodeGen
   MipsSubtarget.cpp
   MipsTargetAsmInfo.cpp
   MipsTargetMachine.cpp
+  MipsTargetObjectFile.cpp
   )
 
 target_link_libraries (LLVMMipsCodeGen LLVMSelectionDAG)

lib/Target/Mips/MipsISelLowering.cpp

@@ -13,10 +13,10 @@
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "mips-lower"
-
 #include "MipsISelLowering.h"
 #include "MipsMachineFunction.h"
 #include "MipsTargetMachine.h"
+#include "MipsTargetObjectFile.h"
 #include "MipsSubtarget.h"
 #include "llvm/DerivedTypes.h"
 #include "llvm/Function.h"
@@ -30,7 +30,6 @@
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/SelectionDAGISel.h"
 #include "llvm/CodeGen/ValueTypes.h"
-#include "llvm/Target/TargetLoweringObjectFile.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 using namespace llvm;
@@ -54,7 +53,7 @@ const char *MipsTargetLowering::getTargetNodeName(unsigned Opcode) const {
 
 MipsTargetLowering::
 MipsTargetLowering(MipsTargetMachine &TM)
-  : TargetLowering(TM, new TargetLoweringObjectFileELF()) {
+  : TargetLowering(TM, new MipsTargetObjectFile()) {
   Subtarget = &TM.getSubtarget<MipsSubtarget>();
 
   // Mips does not have i1 type, so use i32 for
@@ -210,37 +209,6 @@ AddLiveIn(MachineFunction &MF, unsigned PReg, TargetRegisterClass *RC)
   return VReg;
 }
 
-// A address must be loaded from a small section if its size is less than the 
-// small section size threshold. Data in this section must be addressed using 
-// gp_rel operator.
-bool MipsTargetLowering::IsInSmallSection(unsigned Size) {
-  return (Size > 0 && (Size <= Subtarget->getSSectionThreshold()));
-}
-
-// Discover if this global address can be placed into small data/bss section. 
-bool MipsTargetLowering::IsGlobalInSmallSection(GlobalValue *GV)
-{
-  const TargetData *TD = getTargetData();
-  const GlobalVariable *GVA = dyn_cast<GlobalVariable>(GV);
-
-  if (!GVA)
-    return false;
-  
-  const Type *Ty = GV->getType()->getElementType();
-  unsigned Size = TD->getTypeAllocSize(Ty);
-
-  // if this is a internal constant string, there is a special
-  // section for it, but not in small data/bss.
-  if (GVA->hasInitializer() && GV->hasLocalLinkage()) {
-    Constant *C = GVA->getInitializer();
-    const ConstantArray *CVA = dyn_cast<ConstantArray>(C);
-    if (CVA && CVA->isCString()) 
-      return false;
-  }
-
-  return IsInSmallSection(Size);
-}
-
 // Get fp branch code (not opcode) from condition code.
 static Mips::FPBranchCode GetFPBranchCodeFromCond(Mips::CondCode CC) {
   if (CC >= Mips::FCOND_F && CC <= Mips::FCOND_NGT)
@@ -525,8 +493,10 @@ SDValue MipsTargetLowering::LowerGlobalAddress(SDValue Op, SelectionDAG &DAG) {
   if (getTargetMachine().getRelocationModel() != Reloc::PIC_) {
     SDVTList VTs = DAG.getVTList(MVT::i32);
     
+    MipsTargetObjectFile &TLOF = (MipsTargetObjectFile&)getObjFileLowering();
+    
     // %gp_rel relocation
-    if (!isa<Function>(GV) && IsGlobalInSmallSection(GV)) { 
+    if (TLOF.IsGlobalInSmallSection(GV, getTargetMachine())) { 
       SDValue GPRelNode = DAG.getNode(MipsISD::GPRel, dl, VTs, &GA, 1);
       SDValue GOT = DAG.getGLOBAL_OFFSET_TABLE(MVT::i32);
       return DAG.getNode(ISD::ADD, dl, MVT::i32, GOT, GPRelNode); 

lib/Target/Mips/MipsISelLowering.h

@@ -88,8 +88,6 @@ namespace llvm {
     // Subtarget Info
     const MipsSubtarget *Subtarget;
 
-    bool IsGlobalInSmallSection(GlobalValue *GV); 
-    bool IsInSmallSection(unsigned Size); 
 
     // Lower Operand helpers
     SDValue LowerCallResult(SDValue Chain, SDValue InFlag,

lib/Target/Mips/MipsSubtarget.cpp

@@ -14,14 +14,8 @@
 #include "MipsSubtarget.h"
 #include "Mips.h"
 #include "MipsGenSubtarget.inc"
-#include "llvm/Support/CommandLine.h"
 using namespace llvm;
 
-static cl::opt<unsigned>
-SSThreshold("mips-ssection-threshold", cl::Hidden,
-            cl::desc("Small data and bss section threshold size (default=8)"),
-            cl::init(8));
-
 MipsSubtarget::MipsSubtarget(const std::string &TT, const std::string &FS,
                              bool little) : 
   MipsArchVersion(Mips1), MipsABI(O32), IsLittle(little), IsSingleFloat(false),
@@ -35,9 +29,6 @@ MipsSubtarget::MipsSubtarget(const std::string &TT, const std::string &FS,
   // Parse features string.
   ParseSubtargetFeatures(FS, CPU);
 
-  // Small section size threshold
-  SSectionThreshold = SSThreshold;
-
   // Is the target system Linux ?
   if (TT.find("linux") == std::string::npos)
     IsLinux = false;

lib/Target/Mips/MipsSubtarget.h

@@ -60,10 +60,6 @@ protected:
   // isLinux - Target system is Linux. Is false we consider ELFOS for now.
   bool IsLinux;
 
-  // Put global and static items less than or equal to SSectionThreshold 
-  // bytes into the small data or bss section. The default is 8.
-  unsigned SSectionThreshold;
-
   /// Features related to the presence of specific instructions.
   
   // HasSEInReg - SEB and SEH (signext in register) instructions.
@@ -113,7 +109,6 @@ public:
   bool isNotSingleFloat() const { return !IsSingleFloat; };
   bool hasVFPU() const { return HasVFPU; };
   bool isLinux() const { return IsLinux; };
-  unsigned getSSectionThreshold() const { return SSectionThreshold; }
 
   /// Features related to the presence of specific instructions.
   bool hasSEInReg()   const { return HasSEInReg; };

lib/Target/Mips/MipsTargetObjectFile.cpp

@@ -0,0 +1,93 @@
+//===-- MipsTargetObjectFile.cpp - Mips object files ----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "MipsTargetObjectFile.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/GlobalVariable.h"
+#include "llvm/MC/MCSectionELF.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Support/CommandLine.h"
+using namespace llvm;
+
+static cl::opt<unsigned>
+SSThreshold("mips-ssection-threshold", cl::Hidden,
+            cl::desc("Small data and bss section threshold size (default=8)"),
+            cl::init(8));
+
+void MipsTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM){
+  TargetLoweringObjectFileELF::Initialize(Ctx, TM);
+ 
+  SmallDataSection =
+    getELFSection(".sdata", MCSectionELF::SHT_PROGBITS,
+                  MCSectionELF::SHF_WRITE | MCSectionELF::SHF_ALLOC,
+                  SectionKind::getDataRel());
+  
+  SmallBSSSection =
+    getELFSection(".sbss", MCSectionELF::SHT_NOBITS,
+                  MCSectionELF::SHF_WRITE | MCSectionELF::SHF_ALLOC,
+                  SectionKind::getBSS());
+  
+}
+
+// A address must be loaded from a small section if its size is less than the 
+// small section size threshold. Data in this section must be addressed using 
+// gp_rel operator.
+static bool IsInSmallSection(uint64_t Size) {
+  return Size > 0 && Size <= SSThreshold;
+}
+
+bool MipsTargetObjectFile::IsGlobalInSmallSection(const GlobalValue *GV,
+                                                const TargetMachine &TM) const {
+  if (GV->isDeclaration() || GV->hasAvailableExternallyLinkage())
+    return false;
+  
+  return IsGlobalInSmallSection(GV, TM, getKindForGlobal(GV, TM));
+}
+
+/// IsGlobalInSmallSection - Return true if this global address should be
+/// placed into small data/bss section.
+bool MipsTargetObjectFile::
+IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM,
+                       SectionKind Kind) const {
+  // Only global variables, not functions.
+  const GlobalVariable *GVA = dyn_cast<GlobalVariable>(GV);
+  if (!GVA)
+    return false;
+  
+  // We can only do this for datarel or BSS objects for now.
+  if (!Kind.isBSS() && !Kind.isDataRel())
+    return false;
+  
+  // If this is a internal constant string, there is a special
+  // section for it, but not in small data/bss.
+  if (Kind.isMergeable1ByteCString())
+    return false;
+
+  const Type *Ty = GV->getType()->getElementType();
+  return IsInSmallSection(TM.getTargetData()->getTypeAllocSize(Ty));
+}
+
+
+
+const MCSection *MipsTargetObjectFile::
+SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
+                       Mangler *Mang, const TargetMachine &TM) const {
+  // TODO: Could also support "weak" symbols as well with ".gnu.linkonce.s.*"
+  // sections?
+  
+  // Handle Small Section classification here.
+  if (Kind.isBSS() && IsGlobalInSmallSection(GV, TM, Kind))
+    return SmallBSSSection;
+  if (Kind.isDataNoRel() && IsGlobalInSmallSection(GV, TM, Kind))
+    return SmallDataSection;
+  
+  // Otherwise, we work the same as ELF.
+  return TargetLoweringObjectFileELF::SelectSectionForGlobal(GV, Kind, Mang,TM);
+}

lib/Target/Mips/MipsTargetObjectFile.h

@@ -0,0 +1,41 @@
+//===-- llvm/Target/MipsTargetObjectFile.h - Mips Object Info ---*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TARGET_MIPS_TARGETOBJECTFILE_H
+#define LLVM_TARGET_MIPS_TARGETOBJECTFILE_H
+
+#include "llvm/Target/TargetLoweringObjectFile.h"
+
+namespace llvm {
+
+  class MipsTargetObjectFile : public TargetLoweringObjectFileELF {
+    const MCSection *SmallDataSection;
+    const MCSection *SmallBSSSection;
+  public:
+    
+    void Initialize(MCContext &Ctx, const TargetMachine &TM);
+
+    
+    /// IsGlobalInSmallSection - Return true if this global address should be
+    /// placed into small data/bss section.
+    bool IsGlobalInSmallSection(const GlobalValue *GV,
+                                const TargetMachine &TM, SectionKind Kind)const;
+    bool IsGlobalInSmallSection(const GlobalValue *GV,
+                                const TargetMachine &TM) const;  
+    
+    const MCSection *SelectSectionForGlobal(const GlobalValue *GV,
+                                            SectionKind Kind,
+                                            Mangler *Mang,
+                                            const TargetMachine &TM) const;
+      
+    // TODO: Classify globals as mips wishes.
+  };
+} // end namespace llvm
+
+#endif

test/CodeGen/Mips/2008-07-15-SmallSection.ll

@@ -0,0 +1,32 @@
+; RUN: llvm-as < %s | llc -mips-ssection-threshold=8 -march=mips -f -o %t0
+; RUN: llvm-as < %s | llc -mips-ssection-threshold=0 -march=mips -f -o %t1
+; RUN: grep {sdata} %t0 | count 1
+; RUN: grep {sbss} %t0 | count 1
+; RUN: grep {gp_rel} %t0 | count 2
+; RUN: not grep {sdata} %t1 
+; RUN: not grep {sbss} %t1 
+; RUN: not grep {gp_rel} %t1
+; RUN: grep {\%hi} %t1 | count 2
+; RUN: grep {\%lo} %t1 | count 2
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:32-i16:16:32-i32:32:32-i64:32:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64"
+target triple = "mipsallegrexel-psp-elf"
+
+  %struct.anon = type { i32, i32 }
+@s0 = global [8 x i8] c"AAAAAAA\00", align 4
+@foo = global %struct.anon { i32 2, i32 3 }
+@bar = global %struct.anon zeroinitializer 
+
+define i8* @A0() nounwind {
+entry:
+	ret i8* getelementptr ([8 x i8]* @s0, i32 0, i32 0)
+}
+
+define i32 @A1() nounwind {
+entry:
+  load i32* getelementptr (%struct.anon* @foo, i32 0, i32 0), align 8 
+  load i32* getelementptr (%struct.anon* @foo, i32 0, i32 1), align 4 
+  add i32 %1, %0
+  ret i32 %2
+}
+