* Fix one more bug in PIC codegen: extra load is needed for *all*

non-statics.
* Introduce new option to output zero-initialized data to .bss section.
This can reduce size of binaries. Enable it by default for ELF &
Cygwin/Mingw targets. Probably, Darwin should be also added.

llvm-svn: 33299

5 files changed, 31 insertions, 16 deletions

diff --git a/llvm/lib/Target/TargetAsmInfo.cpp b/llvm/lib/Target/TargetAsmInfo.cpp
index b1845007440..b90eaa16689 100644
--- a/llvm/lib/Target/TargetAsmInfo.cpp
+++ b/llvm/lib/Target/TargetAsmInfo.cpp
@@ -19,6 +19,7 @@ using namespace llvm;
 TargetAsmInfo::TargetAsmInfo() :
   TextSection(".text"),
   DataSection(".data"),
+  BSSSection(".bss"),
   AddressSize(4),
   NeedsSet(false),
   MaxInstLength(4),
diff --git a/llvm/lib/Target/TargetMachine.cpp b/llvm/lib/Target/TargetMachine.cpp
index 7547614a717..f6b3fd09f0b 100644
--- a/llvm/lib/Target/TargetMachine.cpp
+++ b/llvm/lib/Target/TargetMachine.cpp
@@ -28,6 +28,7 @@ namespace llvm {
   bool UnsafeFPMath;
   bool FiniteOnlyFPMathOption;
   bool UseSoftFloat;
+  bool NoZerosInBSS;
   Reloc::Model RelocationModel;
   CodeModel::Model CMModel;
 }
@@ -61,6 +62,11 @@ namespace {
                cl::desc("Generate software floating point library calls"),
                cl::location(UseSoftFloat),
                cl::init(false));
+  cl::opt<bool, true>
+  DontPlaceZerosInBSS("nozero-initialized-in-bss",
+               cl::desc("Don't place zero-initialized symbols into bss section"),
+               cl::location(NoZerosInBSS),
+               cl::init(false));
 
   cl::opt<llvm::Reloc::Model, true>
   DefRelocationModel(
diff --git a/llvm/lib/Target/X86/X86ATTAsmPrinter.cpp b/llvm/lib/Target/X86/X86ATTAsmPrinter.cpp
index 02faf7cdb39..1dd53c7a02a 100755
--- a/llvm/lib/Target/X86/X86ATTAsmPrinter.cpp
+++ b/llvm/lib/Target/X86/X86ATTAsmPrinter.cpp
@@ -323,22 +323,19 @@ void X86ATTAsmPrinter::printOperand(const MachineInstr *MI, unsigned OpNo,
       O << Offset;
 
     if (isMemOp) {
-      if (isExt) {
-        if (Subtarget->isPICStyleGOT()) {
+      if (Subtarget->isPICStyleGOT()) {
+        if (Subtarget->GVRequiresExtraLoad(GV, TM, false))
           O << "@GOT";
-        } else if (Subtarget->isPICStyleRIPRel()) {
+        else
+          O << "@GOTOFF";
+      } else     
+        if (isExt && Subtarget->isPICStyleRIPRel())
           O << "@GOTPCREL(%rip)";
-        } else if (Subtarget->is64Bit() && !NotRIPRel)
-            // Use rip when possible to reduce code size, except when
-            // index or base register are also part of the address. e.g.
-            // foo(%rip)(%rcx,%rax,4) is not legal
-            O << "(%rip)";
-      } else {
-        if (Subtarget->is64Bit() && !NotRIPRel)
+        else if (Subtarget->is64Bit() && !NotRIPRel)
+          // Use rip when possible to reduce code size, except when
+          // index or base register are also part of the address. e.g.
+          // foo(%rip)(%rcx,%rax,4) is not legal
           O << "(%rip)";
-        else if (Subtarget->isPICStyleGOT())
-          O << "@GOTOFF";
-      }
     }
 
     return;
diff --git a/llvm/lib/Target/X86/X86AsmPrinter.cpp b/llvm/lib/Target/X86/X86AsmPrinter.cpp
index 767ab23ce3b..bea3914fe64 100644
--- a/llvm/lib/Target/X86/X86AsmPrinter.cpp
+++ b/llvm/lib/Target/X86/X86AsmPrinter.cpp
@@ -28,6 +28,7 @@
 #include "llvm/Assembly/Writer.h"
 #include "llvm/Support/Mangler.h"
 #include "llvm/Target/TargetAsmInfo.h"
+#include "llvm/Target/TargetOptions.h"
 using namespace llvm;
 
 static X86FunctionInfo calculateFunctionInfo(const Function *F,
@@ -149,7 +150,10 @@ bool X86SharedAsmPrinter::doFinalization(Module &M) {
           O << "\t.zerofill __DATA__, __common, " << name << ", "
             << Size << ", " << Align;
       } else {
-        SwitchToDataSection(TAI->getDataSection(), I);
+        if (!NoZerosInBSS && TAI->getBSSSection())
+          SwitchToDataSection(TAI->getBSSSection(), I);
+        else
+          SwitchToDataSection(TAI->getDataSection(), I);
         if (TAI->getLCOMMDirective() != NULL) {
           if (I->hasInternalLinkage()) {
             O << TAI->getLCOMMDirective() << name << "," << Size;
@@ -224,7 +228,10 @@ bool X86SharedAsmPrinter::doFinalization(Module &M) {
 
           SwitchToDataSection(SectionName.c_str());
         } else {
-          SwitchToDataSection(TAI->getDataSection(), I);
+          if (C->isNullValue() && !NoZerosInBSS && TAI->getBSSSection())
+            SwitchToDataSection(TAI->getBSSSection(), I);
+          else
+            SwitchToDataSection(TAI->getDataSection(), I);
         }
         
         break;
diff --git a/llvm/lib/Target/X86/X86Subtarget.cpp b/llvm/lib/Target/X86/X86Subtarget.cpp
index 5f2342ff4d3..be5c64d6d3b 100644
--- a/llvm/lib/Target/X86/X86Subtarget.cpp
+++ b/llvm/lib/Target/X86/X86Subtarget.cpp
@@ -36,10 +36,14 @@ bool X86Subtarget::GVRequiresExtraLoad(const GlobalValue* GV,
                                        bool isDirectCall) const
 {
   if (TM.getRelocationModel() != Reloc::Static)
-    if (isTargetDarwin() || isPICStyleGOT()) {
+    if (isTargetDarwin()) {
       return (!isDirectCall &&
               (GV->hasWeakLinkage() || GV->hasLinkOnceLinkage() ||
                (GV->isExternal() && !GV->hasNotBeenReadFromBytecode())));
+    } else if (isPICStyleGOT()) {
+      // Extra load is needed for all non-statics.
+      return (!isDirectCall &&
+              (GV->isExternal() || !GV->hasInternalLinkage()));
     } else if (isTargetCygMing() || isTargetWindows()) {
       return (GV->hasDLLImportLinkage());
     }