Make DW_AT_[MIPS_]linkage_name optional, and off by default for SCE.

Mangled "linkage" names can be huge, and if the debugger (or other
tools) have no use for them, the size savings can be very impressive
(on the order of 40%).

Add one test for controlling behavior, and modify a number of tests to
either stop using linkage names, or make llc emit them (so these tests
will still run when the default triple is for PS4).

Differential Revision: http://reviews.llvm.org/D11374

llvm-svn: 244678

3 files changed, 21 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index e09a90fbd0b..4a673d49ced 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -116,6 +116,14 @@ DwarfPubSections("generate-dwarf-pub-sections", cl::Hidden,
                             clEnumVal(Disable, "Disabled"), clEnumValEnd),
                  cl::init(Default));
 
+static cl::opt<DefaultOnOff>
+DwarfLinkageNames("dwarf-linkage-names", cl::Hidden,
+                  cl::desc("Emit DWARF linkage-name attributes."),
+                  cl::values(clEnumVal(Default, "Default for platform"),
+                             clEnumVal(Enable, "Enabled"),
+                             clEnumVal(Disable, "Disabled"), clEnumValEnd),
+                  cl::init(Default));
+
 static const char *const DWARFGroupName = "DWARF Emission";
 static const char *const DbgTimerName = "DWARF Debug Writer";
 
@@ -250,6 +258,12 @@ DwarfDebug::DwarfDebug(AsmPrinter *A, Module *M)
   else
     HasDwarfPubSections = DwarfPubSections == Enable;
 
+  // SCE does not use linkage names.
+  if (DwarfLinkageNames == Default)
+    UseLinkageNames = !tuneForSCE();
+  else
+    UseLinkageNames = DwarfLinkageNames == Enable;
+
   unsigned DwarfVersionNumber = Asm->TM.Options.MCOptions.DwarfVersion;
   DwarfVersion = DwarfVersionNumber ? DwarfVersionNumber
                                     : MMI->getModule()->getDwarfVersion();
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
index d17589cba9e..977f3406441 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -333,6 +333,9 @@ class DwarfDebug : public AsmPrinterHandler {
   /// Whether to use the GNU TLS opcode (instead of the standard opcode).
   bool UseGNUTLSOpcode;
 
+  /// Whether to emit DW_AT_[MIPS_]linkage_name.
+  bool UseLinkageNames;
+
   /// Version of dwarf we're emitting.
   unsigned DwarfVersion;
 
@@ -588,6 +591,9 @@ public:
     SymSize[Sym] = Size;
   }
 
+  /// Returns whether to emit DW_AT_[MIPS_]linkage_name.
+  bool useLinkageNames() const { return UseLinkageNames; }
+
   /// Returns whether to use DW_OP_GNU_push_tls_address, instead of the
   /// standard DW_OP_form_tls_address opcode
   bool useGNUTLSOpcode() const { return UseGNUTLSOpcode; }
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 72b9fe7fd8f..d5ed0cd0945 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -667,7 +667,7 @@ void DwarfUnit::addConstantValue(DIE &Die, const APInt &Val, bool Unsigned) {
 }
 
 void DwarfUnit::addLinkageName(DIE &Die, StringRef LinkageName) {
-  if (!LinkageName.empty())
+  if (!LinkageName.empty() && DD->useLinkageNames())
     addString(Die,
               DD->getDwarfVersion() >= 4 ? dwarf::DW_AT_linkage_name
                                          : dwarf::DW_AT_MIPS_linkage_name,