A CIL Tutorial - Department of Computer Science - ETH Zürich

CHAPTER 10. ADDING A NEW KIND OF STATEMENT 83
The cacheReportAdder visitor nds statements satisfying isCacheReportStmt, and brackets the
statements nested within them inside of the calls to our runtime, which are given by makeCacheReportStmts.
class cacheReportAdder = object(self)
inherit nopCilVisitor
method vstmt (s : stmt) =
let action s =
match isCacheReportStmt s with
| Some b → begin
let bs, es = makeCacheReportStmts (get stmtLoc s.skind) in
let nb = mkBlock [bs; mkStmt(Block b); es] in
s.skind ← Block nb;
s
end
| None → s
in
ChangeDoChildrenPost(s, action)
end
The function tut10 is the entry point to this module.
invokes the cacheReportAdder visitor on the le f.
It Initializes the runtime functions, and
let tut10 (f : file) : unit =
initCacheFunctions f;
let vis = new cacheReportAdder in
visitCilFile vis f
Now we describe all of the hard work that takes place inside of the C functions tut cache begin and
tut cache end. In addition we must explain the data structures used to maintain per-thread state,
and the method for reading the hardware performance counters for cache misses and references.
10.2 tut10.c
This C source le contains the implementation of the runtime for the cache report statement. It
must accomplish three things. First, each thread must use Linux's perf event open system call to
access the hardware performance counters for cache misses and references. Secondly, each thread
must maintain a stack that mirrors the nesting structure of the cache report statement. Finally,
we must use the dynamic linker to override the C Library function pthread create to ensure that
new threads are set up to access the performance counters and to maintain the stack.