Fix bug: forgot branchTarget() method on indirect branches.

arch/alpha/isa_desc:
    Add missing branchTarget() method for indirect branches.
cpu/static_inst.hh:
    Add comment clarifying when branchTarget() can be used
    on indirect branches.

--HG--
extra : convert_revision : 0dcfb36a9792a338cefceb3d1501825abace7ac5

arch/alpha/isa_desc

@@ -1287,6 +1287,13 @@ declare {{
 	{
 	}
 
+	Addr branchTarget(ExecContext *xc)
+	{
+	    Addr NPC = xc->readPC() + 4;
+	    uint64_t Rb = xc->readIntReg(_srcRegIdx[0]);
+	    return (Rb & ~3) | (NPC & 1);
+	}
+
 	std::string generateDisassembly(Addr pc, const SymbolTable *symtab)
 	{
 	    std::stringstream ss;

cpu/static_inst.hh

@@ -312,10 +312,11 @@ class StaticInst : public StaticInstBase
     }
 
     /**
-     * Return the target address for an indirect branch (jump).
-     * The register value is read from the supplied execution context.
-     * Invalid if not an indirect branch (i.e. isIndirectCtrl()
-     * should be true).
+     * Return the target address for an indirect branch (jump).  The
+     * register value is read from the supplied execution context, so
+     * the result is valid only if the execution context is about to
+     * execute the branch in question.  Invalid if not an indirect
+     * branch (i.e. isIndirectCtrl() should be true).
      */
     virtual Addr branchTarget(ExecContext *xc)
     {