Optimizer - So, UD chains are broken

Disabled broken code and added some notes, which are probably broken as
well but fuck it.

c-opopt.cc

@@ -634,6 +634,30 @@ void T_OptData::buildUseDefineChains(
 		BUDCAddEntries_( udPerInstr , i , false , r.defines );
 	}
 
+
+	/*
+	 * So this whole heap of code below is wrong. It wouldn't work correctly
+	 * in all cases (although it does with the current test code, but that's
+	 * irrelevant).
+	 *
+	 * A block B from the CFG has instr{B}+1 points (1 point before each
+	 * instruction, and 1 point at the end of the block).
+	 *
+	 * Uses should be assigned to the point preceding the instruction; defs
+	 * and kills should be assigned to the point that follows it, before
+	 * any uses (it may be simpler to have 2 points / instruction?)
+	 *
+	 *               defs from I0         defs from I1
+	 *              \/                   \/
+	 * P00 -> I0 -> P01 -> P10 -> I1 -> I11 -> PBE
+	 *  /\                  /\                  /\
+	 *   uses from I0        uses from I1        defs/kills from block end
+	 *
+	 * Entering/exiting functions is a bit of a PITA:
+	 *	- call instructions define function arguments;
+	 *	- return edges kill locals
+	 */
+#if 0
 	// Walk the graph from the entry point until all reachable nodes
 	// have been covered and keeping track of active definitions. When
 	// the flow diverges, we need to store the state before the
@@ -785,6 +809,7 @@ void T_OptData::buildUseDefineChains(
 
 		// 30 if next block is an end of function, kill locals
 	}
+#endif
 }