Revert "Generalized assignment rewriting pass."

This reverts commit 2ec79623.

compiler/cmm/CmmCPS.hs

@@ -95,8 +95,9 @@ cpsTop hsc_env (CmmProc h@(TopInfo {stack_info=StackInfo {arg_space=entry_off}})
                              (dualLivenessWithInsertion procPoints) g
                     -- Insert spills at defns; reloads at return points
        g     <-
-                runOptimization $ rewriteAssignments g
-       dump Opt_D_dump_cmmz "Post rewrite assignments" g
+              -- pprTrace "pre insertLateReloads" (ppr g) $
+                runOptimization $ insertLateReloads g -- Duplicate reloads just before uses
+       dump Opt_D_dump_cmmz "Post late reloads" g
        g     <-
                -- pprTrace "post insertLateReloads" (ppr g) $
                 dual_rewrite runOptimization Opt_D_dump_cmmz "Dead Assignment Elimination"