Extend Architecture to help retrieve return values.

- Architecture now has a new function to retrieve the location where
  a return value can be found. Added implementation for x86 and stub
  for x86-64.

src/apps/debugger/arch/Architecture.h

@@ -30,6 +30,7 @@ class StackTrace;
 class Statement;
 class Team;
 class TeamMemory;
+class ValueLocation;
 
 
 enum {
@@ -118,6 +119,10 @@ public:
 									int32& _maxBytesPerRegister,
 									uint8& _watchpointCapabilityFlags) = 0;
 
+	virtual	status_t			GetReturnAddressLocation(
+									StackFrame* frame, target_size_t valueSize,
+									ValueLocation*& _location) = 0;
+
 
 protected:
 			TeamMemory*			fTeamMemory;

src/apps/debugger/arch/x86/ArchitectureX86.cpp

@@ -23,6 +23,7 @@
 #include "StackFrame.h"
 #include "Statement.h"
 #include "TeamMemory.h"
+#include "ValueLocation.h"
 #include "X86AssemblyLanguage.h"
 
 #include "disasm/DisassemblerX86.h"
@@ -579,9 +580,8 @@ status_t
 ArchitectureX86::GetInstructionInfo(target_addr_t address,
 	InstructionInfo& _info)
 {
-	// read the code
+	// read the code - maximum x86{-64} instruction size = 15 bytes
 	uint8 buffer[16];
-		// TODO: What's the maximum instruction size?
 	ssize_t bytesRead = fTeamMemory->ReadMemory(address, buffer,
 		sizeof(buffer));
 	if (bytesRead < 0)
@@ -648,6 +648,52 @@ ArchitectureX86::GetWatchpointDebugCapabilities(int32& _maxRegisterCount,
 }
 
 
+status_t
+ArchitectureX86::GetReturnAddressLocation(StackFrame* frame,
+	target_size_t valueSize, ValueLocation*& _location)
+{
+	// for the calling conventions currently in use on Haiku,
+	// the x86 rules for how values are returned are as follows:
+	//
+	// - 32 bits or smaller values are returned directly in EAX.
+	// - 32-64 bit values are returned across EAX:EDX.
+	// - > 64 bit values are returned on the stack.
+	ValueLocation* location = new(std::nothrow) ValueLocation(
+		IsBigEndian());
+	if (location == NULL)
+		return B_NO_MEMORY;
+	BReference<ValueLocation> locationReference(location,
+		true);
+
+	if (valueSize <= 4) {
+		ValuePieceLocation piece;
+		piece.SetSize(valueSize);
+		piece.SetToRegister(X86_REGISTER_EAX);
+		if (!location->AddPiece(piece))
+			return B_NO_MEMORY;
+	} else if (valueSize <= 8) {
+		ValuePieceLocation piece;
+		piece.SetSize(4);
+		piece.SetToRegister(X86_REGISTER_EAX);
+		if (!location->AddPiece(piece))
+			return B_NO_MEMORY;
+		piece.SetToRegister(X86_REGISTER_EDX);
+		piece.SetSize(valueSize - 4);
+		if (!location->AddPiece(piece))
+			return B_NO_MEMORY;
+	} else {
+		ValuePieceLocation piece;
+		piece.SetToMemory(frame->GetCpuState()->StackPointer());
+		piece.SetSize(valueSize);
+		if (!location->AddPiece(piece))
+			return B_NO_MEMORY;
+	}
+
+	_location = locationReference.Detach();
+	return B_OK;
+}
+
+
 void
 ArchitectureX86::_AddRegister(int32 index, const char* name,
 	uint32 bitSize, uint32 valueType, register_type type, bool calleePreserved)

src/apps/debugger/arch/x86/ArchitectureX86.h

@@ -66,6 +66,11 @@ public:
 									int32& _maxBytesPerRegister,
 									uint8& _watchpointCapabilityFlags);
 
+	virtual	status_t			GetReturnAddressLocation(
+									StackFrame* frame, target_size_t valueSize,
+									ValueLocation*& _location);
+
+
 private:
 			struct ToDwarfRegisterMap;
 			struct FromDwarfRegisterMap;

src/apps/debugger/arch/x86_64/ArchitectureX8664.cpp

@@ -535,6 +535,13 @@ ArchitectureX8664::GetWatchpointDebugCapabilities(int32& _maxRegisterCount,
 }
 
 
+status_t
+ArchitectureX8664::GetReturnAddressLocation(StackFrame* frame,
+	target_size_t valueSize, ValueLocation*& _location) {
+	return B_NOT_SUPPORTED;
+}
+
+
 void
 ArchitectureX8664::_AddRegister(int32 index, const char* name,
 	uint32 bitSize, uint32 valueType, register_type type, bool calleePreserved)

src/apps/debugger/arch/x86_64/ArchitectureX8664.h

@@ -67,6 +67,10 @@ public:
 									int32& _maxBytesPerRegister,
 									uint8& _watchpointCapabilityFlags);
 
+	virtual	status_t			GetReturnAddressLocation(
+									StackFrame* frame, target_size_t valueSize,
+									ValueLocation*& _location);
+
 private:
 			struct ToDwarfRegisterMap;
 			struct FromDwarfRegisterMap;