Use .cfi_sections to put the unwind info in .debug_frame when possible. With

this clang will use .debug_frame in, for example,
clang -g -c -m32 test.c
This matches gcc's behaviour. It looks like .debug_frame is a bit bigger
than .eh_frame, but has the big advantage of not being allocated.

llvm-svn: 131140

llvm/include/llvm/CodeGen/AsmPrinter.h

@@ -185,7 +185,12 @@ namespace llvm {
 
     void emitPrologLabel(const MachineInstr &MI);
 
-    bool needsCFIMoves();
+    enum CFIMoveType {
+      CFI_M_None,
+      CFI_M_EH,
+      CFI_M_Debug
+    };
+    CFIMoveType needsCFIMoves();
 
     /// EmitConstantPool - Print to the current output stream assembly
     /// representations of the constants in the constant pool MCP. This is

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -592,17 +592,17 @@ static bool EmitDebugValueComment(const MachineInstr *MI, AsmPrinter &AP) {
   return true;
 }
 
-bool AsmPrinter::needsCFIMoves() {
+AsmPrinter::CFIMoveType AsmPrinter::needsCFIMoves() {
   if (UnwindTablesMandatory)
-    return true;
+    return CFI_M_EH;
+
+  if (!MF->getFunction()->doesNotThrow())
+    return CFI_M_EH;
 
   if (MMI->hasDebugInfo())
-    return true;
+    return CFI_M_Debug;
 
-  if (MF->getFunction()->doesNotThrow())
-    return false;
-
-  return true;
+  return CFI_M_None;
 }
 
 void AsmPrinter::emitPrologLabel(const MachineInstr &MI) {
@@ -611,7 +611,7 @@ void AsmPrinter::emitPrologLabel(const MachineInstr &MI) {
   if (MAI->getExceptionHandlingType() != ExceptionHandling::DwarfCFI)
     return;
 
-  if (!needsCFIMoves())
+  if (needsCFIMoves() == CFI_M_None)
     return;
 
   MachineModuleInfo &MMI = MF->getMMI();

llvm/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp

@@ -49,6 +49,9 @@ DwarfCFIException::~DwarfCFIException() {}
 /// EndModule - Emit all exception information that should come after the
 /// content.
 void DwarfCFIException::EndModule() {
+  if (moveTypeModule == AsmPrinter::CFI_M_Debug)
+    Asm->OutStreamer.EmitCFISections(false, true);
+
   if (!Asm->MAI->isExceptionHandlingDwarf())
     return;
 
@@ -87,7 +90,13 @@ void DwarfCFIException::BeginFunction(const MachineFunction *MF) {
   bool hasLandingPads = !MMI->getLandingPads().empty();
 
   // See if we need frame move info.
-  shouldEmitMoves = Asm->needsCFIMoves();
+  AsmPrinter::CFIMoveType MoveType = Asm->needsCFIMoves();
+  if (MoveType == AsmPrinter::CFI_M_EH ||
+      (MoveType == AsmPrinter::CFI_M_Debug &&
+       moveTypeModule == AsmPrinter::CFI_M_None))
+    moveTypeModule = MoveType;
+
+  shouldEmitMoves = MoveType != AsmPrinter::CFI_M_None;
 
   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
   unsigned PerEncoding = TLOF.getPersonalityEncoding();

llvm/lib/CodeGen/AsmPrinter/DwarfException.h

@@ -15,6 +15,7 @@
 #define LLVM_CODEGEN_ASMPRINTER_DWARFEXCEPTION_H
 
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/CodeGen/AsmPrinter.h"
 #include <vector>
 
 namespace llvm {
@@ -152,6 +153,8 @@ class DwarfCFIException : public DwarfException {
   /// should be emitted.
   bool shouldEmitMoves;
 
+  AsmPrinter::CFIMoveType moveTypeModule;
+
 public:
   //===--------------------------------------------------------------------===//
   // Main entry points.

llvm/test/DebugInfo/debug_frame.ll

@@ -0,0 +1,18 @@
+; RUN: llc %s -o - | FileCheck %s
+
+; Test that we produce a .debug_frame, not an .eh_frame
+
+; CHECK: .cfi_sections .debug_frame
+
+define void @f() nounwind {
+entry:
+  ret void
+}
+
+!llvm.dbg.sp = !{!0}
+
+!0 = metadata !{i32 589870, i32 0, metadata !1, metadata !"f", metadata !"f", metadata !"", metadata !1, i32 1, metadata !3, i1 false, i1 true, i32 0, i32 0, i32 0, i32 256, i1 true, void ()* @f, null, null} ; [ DW_TAG_subprogram ]
+!1 = metadata !{i32 589865, metadata !"/home/espindola/llvm/test.c", metadata !"/home/espindola/llvm/build", metadata !2} ; [ DW_TAG_file_type ]
+!2 = metadata !{i32 589841, i32 0, i32 12, metadata !"/home/espindola/llvm/test.c", metadata !"/home/espindola/llvm/build", metadata !"clang version 3.0 ()", i1 true, i1 true, metadata !"", i32 0} ; [ DW_TAG_compile_unit ]
+!3 = metadata !{i32 589845, metadata !1, metadata !"", metadata !1, i32 0, i64 0, i64 0, i32 0, i32 0, i32 0, metadata !4, i32 0, i32 0} ; [ DW_TAG_subroutine_type ]
+!4 = metadata !{null}