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Author SHA1 Message Date
Jakob Stoklund Olesen eb488fe165 Verify that the CFG hasn't changed during invalidate(). 
The MachineTraceMetrics analysis must be invalidated before modifying
the CFG. This will catch some of the violations of that rule.

llvm-svn: 160969
 2012-07-30 17:36:49 +00:00
Jakob Stoklund Olesen 0563369755 Add more debug output to MachineTraceMetrics. 
llvm-svn: 160905
 2012-07-27 23:58:38 +00:00
Jakob Stoklund Olesen 1152202cc2 Keep track of the head and tail of the trace through each block. 
This makes it possible to quickly detect blocks that are outside the
trace.

llvm-svn: 160904
 2012-07-27 23:58:36 +00:00
Jakob Stoklund Olesen 35400b1dda Use an otherwise unused variable. 
llvm-svn: 160798
 2012-07-26 19:42:56 +00:00
Jakob Stoklund Olesen f9029fef2a Start scaffolding for a MachineTraceMetrics analysis pass. 
This is still a work in progress.

Out-of-order CPUs usually execute instructions from multiple basic
blocks simultaneously, so it is necessary to look at longer traces when
estimating the performance effects of code transformations.

The MachineTraceMetrics analysis will pick a typical trace through a
given basic block and provide performance metrics for the trace. Metrics
will include:

- Instruction count through the trace.
- Issue count per functional unit.
- Critical path length, and per-instruction 'slack'.

These metrics can be used to determine the performance limiting factor
when executing the trace, and how it will be affected by a code
transformation.

Initially, this will be used by the early if-conversion pass.

llvm-svn: 160796
 2012-07-26 18:38:11 +00:00