[llvm-commits] [llvm] r112439 - /llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp

[Dan Gohman]

Author: djg
Date: Sun Aug 29 11:09:42 2010
New Revision: 112439

URL: http://llvm.org/viewvc/llvm-project?rev=112439&view=rev
Log:
Refactor the three main groups of code out of
NarrowSearchSpaceUsingHeuristics into separate functions.

Modified:
    llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp?rev=112439&r1=112438&r2=112439&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp Sun Aug 29 11:09:42 2010
@@ -1367,6 +1367,9 @@
   void FilterOutUndesirableDedicatedRegisters();
 
   size_t EstimateSearchSpaceComplexity() const;
+  void NarrowSearchSpaceByDetectingSupersets();
+  void NarrowSearchSpaceByCollapsingUnrolledCode();
+  void NarrowSearchSpaceByPickingWinnerRegs();
   void NarrowSearchSpaceUsingHeuristics();
 
   void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
@@ -2905,11 +2908,11 @@
   return Power;
 }
 
-/// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of
-/// formulae to choose from, use some rough heuristics to prune down the number
-/// of formulae. This keeps the main solver from taking an extraordinary amount
-/// of time in some worst-case scenarios.
-void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
+/// NarrowSearchSpaceByDetectingSupersets - When one formula uses a superset
+/// of the registers of another formula, it won't help reduce register
+/// pressure (though it may not necessarily hurt register pressure); remove
+/// it to simplify the system.
+void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
   if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
     DEBUG(dbgs() << "The search space is too complex.\n");
 
@@ -2967,7 +2970,12 @@
     DEBUG(dbgs() << "After pre-selection:\n";
           print_uses(dbgs()));
   }
+}
 
+/// NarrowSearchSpaceByCollapsingUnrolledCode - When there are many registers
+/// for expressions like A, A+1, A+2, etc., allocate a single register for
+/// them.
+void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
   if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
     DEBUG(dbgs() << "The search space is too complex.\n");
 
@@ -3038,7 +3046,12 @@
     DEBUG(dbgs() << "After pre-selection:\n";
           print_uses(dbgs()));
   }
+}
 
+/// NarrowSearchSpaceByPickingWinnerRegs - Pick a register which seems likely
+/// to be profitable, and then in any use which has any reference to that
+/// register, delete all formulae which do not reference that register.
+void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
   // With all other options exhausted, loop until the system is simple
   // enough to handle.
   SmallPtrSet<const SCEV *, 4> Taken;
@@ -3100,6 +3113,16 @@
   }
 }
 
+/// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of
+/// formulae to choose from, use some rough heuristics to prune down the number
+/// of formulae. This keeps the main solver from taking an extraordinary amount
+/// of time in some worst-case scenarios.
+void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
+  NarrowSearchSpaceByDetectingSupersets();
+  NarrowSearchSpaceByCollapsingUnrolledCode();
+  NarrowSearchSpaceByPickingWinnerRegs();
+}
+
 /// SolveRecurse - This is the recursive solver.
 void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
                                Cost &SolutionCost,