Add trace accessor methods, implement primitive if-conversion heuristic.
Compare the critical paths of the two traces through an if-conversion
candidate. If the difference is larger than the branch brediction
penalty, reject the if-conversion. If would never pay.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161433 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineTraceMetrics.h b/lib/CodeGen/MachineTraceMetrics.h
index 33c2d95..626b28b 100644
--- a/lib/CodeGen/MachineTraceMetrics.h
+++ b/lib/CodeGen/MachineTraceMetrics.h
@@ -188,23 +188,6 @@
void print(raw_ostream&) const;
};
- /// A trace represents a plausible sequence of executed basic blocks that
- /// passes through the current basic block one. The Trace class serves as a
- /// handle to internal cached data structures.
- class Trace {
- Ensemble &TE;
- TraceBlockInfo &TBI;
-
- public:
- explicit Trace(Ensemble &te, TraceBlockInfo &tbi) : TE(te), TBI(tbi) {}
- void print(raw_ostream&) const;
-
- /// Compute the total number of instructions in the trace.
- unsigned getInstrCount() const {
- return TBI.InstrDepth + TBI.InstrHeight;
- }
- };
-
/// InstrCycles represents the cycle height and depth of an instruction in a
/// trace.
struct InstrCycles {
@@ -218,6 +201,48 @@
unsigned Height;
};
+ /// A trace represents a plausible sequence of executed basic blocks that
+ /// passes through the current basic block one. The Trace class serves as a
+ /// handle to internal cached data structures.
+ class Trace {
+ Ensemble &TE;
+ TraceBlockInfo &TBI;
+
+ unsigned getBlockNum() const { return &TBI - &TE.BlockInfo[0]; }
+
+ public:
+ explicit Trace(Ensemble &te, TraceBlockInfo &tbi) : TE(te), TBI(tbi) {}
+ void print(raw_ostream&) const;
+
+ /// Compute the total number of instructions in the trace.
+ unsigned getInstrCount() const {
+ return TBI.InstrDepth + TBI.InstrHeight;
+ }
+
+ /// Return the resource dpeth of the top/bottom of the trace center block.
+ /// This is the number of cycles required to execute all instructions from
+ /// the trace head to the trace center block. The resource depth only
+ /// considers execution resources, it ignores data dependencies.
+ /// When Bottom is set, instructions in the trace center block are included.
+ unsigned getResourceDepth(bool Bottom) const;
+
+ /// Return the length of the (data dependency) critical path through the
+ /// trace.
+ unsigned getCriticalPath() const { return TBI.CriticalPath; }
+
+ /// Return the depth and height of MI. The depth is only valid for
+ /// instructions in or above the trace center block. The height is only
+ /// valid for instructions in or below the trace center block.
+ InstrCycles getInstrCycles(const MachineInstr *MI) const {
+ return TE.Cycles.lookup(MI);
+ }
+
+ /// Return the slack of MI. This is the number of cycles MI can be delayed
+ /// before the critical path becomes longer.
+ /// MI must be an instruction in the trace center block.
+ unsigned getInstrSlack(const MachineInstr *MI) const;
+ };
+
/// A trace ensemble is a collection of traces selected using the same
/// strategy, for example 'minimum resource height'. There is one trace for
/// every block in the function.