[MLton-user] experimental release 20051109
Mon, 14 Nov 2005 09:57:26 +0100
* Matthew Fluet:
> A little more investigation reveals that -fno-tree-ch suffices to quell
> the errors. The gcc documentation describes the tree-ch optimization as
> Perform loop header copying on trees. This is beneficial since it
> increases effectiveness of code motion optimizations. It also saves one
> jump. This flag is enabled by default at -O and higher. It is not
> enabled for -Os, since it usually increases code size.
> This agrees with the observed behavior: a loops in SML are almost
> invariably defined by recursive functions, hence would receive a
> distinguished profiling label. MLton successfully translates the
> recursive function into a local loop, with the profiling label in the loop
> (including the header). Duplicating the header duplicates the profile
Looks like a bug in should_duplicate_loop_header_p; it should not flag
volatile asm statements for duplication. However, this is a corner
case because duplication of volatile asm statements usually does not
hurt, as long as only one duplicate is ever executed.
I will check with the GCC folks.