Available debugging options:

     a          show node-matching during simplification
     b          show breakdown of time needed for each compiler pass
     c          print every expression before macro-expansion
     d          lists all assigned global variables
     e          show information about specializations
     h          you already figured that out
     i          show information about inlining
     m          show GC statistics during compilation
     n          print the line-number database 
     o          show performed optimizations
     p          display information about what the compiler is currently doing
     r          show invocation parameters
     s          show program-size information and other statistics
     t          show time needed for compilation
     u          lists all unassigned global variable references
     x          display information about experimental features
     D          when printing nodes, use node-tree output
     I          show inferred type information for unexported globals
     M          show syntax-/runtime-requirements
     N          show the real-name mapping table
     P          show expressions after specialization
     S          show applications of compiler syntax
     T          show expressions after converting to node tree
     1          show source expressions
     2          show canonicalized expressions
     3          show expressions converted into CPS
     4          show database after each analysis pass
     5          show expressions after each optimization pass
     6          show expressions after each inlining pass
     7          show expressions after complete optimization
     8          show database after final analysis
     9          show expressions after closure conversion