Add comment to elaborate on store-conditional result code (and remove

stale reference to machine.def).

arch/alpha/isa_desc:
    Add comment describing store-conditional result code
cpu/exec_context.hh:
    update comments

--HG--
extra : convert_revision : ac59e0ad7a9440cb6656617fdf05495b59c68f55

arch/alpha/isa_desc

@@ -1808,11 +1808,19 @@ decode OPCODE default Unknown::unknown() {
 	0x2e: stl_c({{ EA = Rb + disp; }}, {{ Mem.ul = Ra<31:0>; }},
 		    {{
 			uint64_t tmp = Mem_write_result;
+			// see stq_c
 			Ra = (tmp == 0 || tmp == 1) ? tmp : Ra;
 		    }}, LOCKED);
 	0x2f: stq_c({{ EA = Rb + disp; }}, {{ Mem.uq = Ra; }},
 		    {{
 			uint64_t tmp = Mem_write_result;
+			// If the write operation returns 0 or 1, then
+			// this was a conventional store conditional,
+			// and the value indicates the success/failure
+			// of the operation.  If another value is
+			// returned, then this was a Turbolaser
+			// mailbox access, and we don't update the
+			// result register at all.
 			Ra = (tmp == 0 || tmp == 1) ? tmp : Ra;
 		    }}, LOCKED);
     }

cpu/exec_context.hh

@@ -218,7 +218,7 @@ class ExecContext
             cregs = &req->xc->regs.miscRegs;
 
             if (req->flags & UNCACHEABLE) {
-                // Don't update result register (see machine.def)
+                // Don't update result register (see stq_c in isa_desc)
                 req->result = 2;
                 req->xc->storeCondFailures = 0;//Needed? [RGD]
             } else {
@@ -239,12 +239,11 @@ class ExecContext
             }
         }
 
-        // Need to clear any locked flags on other proccessors for this
-        // address
-        // Only do this for succsful Store Conditionals and all other
-        // stores (WH64?)
-        // Unsuccesful Store Conditionals would have returned above,
-        // and wouldn't fall through
+        // Need to clear any locked flags on other proccessors for
+        // this address.  Only do this for succsful Store Conditionals
+        // and all other stores (WH64?).  Unsuccessful Store
+        // Conditionals would have returned above, and wouldn't fall
+        // through.
         for (int i = 0; i < system->xcvec.size(); i++){
             cregs = &system->xcvec[i]->regs.miscRegs;
             if ((cregs->lock_addr & ~0xf) == (req->paddr & ~0xf)) {