Add getUnrollingPreferences to TTI

Allow targets to customize the default behavior of the generic loop unrolling
transformation. This will be used by the PowerPC backend when targeting the A2
core (which is in-order with a deep pipeline), and using more aggressive
defaults is important.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190542 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 35 insertions, 7 deletions

diff --git a/lib/Analysis/TargetTransformInfo.cpp b/lib/Analysis/TargetTransformInfo.cpp
index 8c6005b..b23223d 100644
--- a/lib/Analysis/TargetTransformInfo.cpp
+++ b/lib/Analysis/TargetTransformInfo.cpp
@@ -96,6 +96,11 @@ bool TargetTransformInfo::isLoweredToCall(const Function *F) const {
   return PrevTTI->isLoweredToCall(F);
 }
 
+void TargetTransformInfo::getUnrollingPreferences(Loop *L,
+                            UnrollingPreferences &UP) const {
+  PrevTTI->getUnrollingPreferences(L, UP);
+}
+
 bool TargetTransformInfo::isLegalAddImmediate(int64_t Imm) const {
   return PrevTTI->isLegalAddImmediate(Imm);
 }
@@ -469,6 +474,8 @@ struct NoTTI : ImmutablePass, TargetTransformInfo {
     return true;
   }
 
+  void getUnrollingPreferences(Loop *, UnrollingPreferences &) const { }
+
   bool isLegalAddImmediate(int64_t Imm) const {
     return false;
   }
diff --git a/lib/CodeGen/BasicTargetTransformInfo.cpp b/lib/CodeGen/BasicTargetTransformInfo.cpp
index d5340e6..9c4b49a 100644
--- a/lib/CodeGen/BasicTargetTransformInfo.cpp
+++ b/lib/CodeGen/BasicTargetTransformInfo.cpp
@@ -84,6 +84,7 @@ public:
   virtual unsigned getJumpBufSize() const;
   virtual bool shouldBuildLookupTables() const;
   virtual bool haveFastSqrt(Type *Ty) const;
+  virtual void getUnrollingPreferences(Loop *L, UnrollingPreferences &UP) const;
 
   /// @}
 
@@ -189,6 +190,8 @@ bool BasicTTI::haveFastSqrt(Type *Ty) const {
   return TLI->isTypeLegal(VT) && TLI->isOperationLegalOrCustom(ISD::FSQRT, VT);
 }
 
+void BasicTTI::getUnrollingPreferences(Loop *, UnrollingPreferences &) const { }
+
 //===----------------------------------------------------------------------===//
 //
 // Calls used by the vectorizers.
diff --git a/lib/Transforms/Scalar/LoopUnrollPass.cpp b/lib/Transforms/Scalar/LoopUnrollPass.cpp
index 80d060b..d47a3c3 100644
--- a/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -55,6 +55,9 @@ namespace {
       CurrentAllowPartial = (P == -1) ? UnrollAllowPartial : (bool)P;
 
       UserThreshold = (T != -1) || (UnrollThreshold.getNumOccurrences() > 0);
+      UserAllowPartial = (P != -1) ||
+                         (UnrollAllowPartial.getNumOccurrences() > 0);
+      UserCount = (C != -1) || (UnrollCount.getNumOccurrences() > 0);
 
       initializeLoopUnrollPass(*PassRegistry::getPassRegistry());
     }
@@ -75,7 +78,9 @@ namespace {
     unsigned CurrentCount;
     unsigned CurrentThreshold;
     bool     CurrentAllowPartial;
+    bool     UserCount;            // CurrentCount is user-specified.
     bool     UserThreshold;        // CurrentThreshold is user-specified.
+    bool     UserAllowPartial;     // CurrentAllowPartial is user-specified.
 
     bool runOnLoop(Loop *L, LPPassManager &LPM);
 
@@ -145,16 +150,24 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
         << "] Loop %" << Header->getName() << "\n");
   (void)Header;
 
+  TargetTransformInfo::UnrollingPreferences UP;
+  UP.Threshold = CurrentThreshold;
+  UP.OptSizeThreshold = OptSizeUnrollThreshold;
+  UP.Count = CurrentCount;
+  UP.Partial = CurrentAllowPartial;
+  UP.Runtime = UnrollRuntime;
+  TTI.getUnrollingPreferences(L, UP);
+
   // Determine the current unrolling threshold.  While this is normally set
   // from UnrollThreshold, it is overridden to a smaller value if the current
   // function is marked as optimize-for-size, and the unroll threshold was
   // not user specified.
-  unsigned Threshold = CurrentThreshold;
+  unsigned Threshold = UserThreshold ? CurrentThreshold : UP.Threshold;
   if (!UserThreshold &&
       Header->getParent()->getAttributes().
         hasAttribute(AttributeSet::FunctionIndex,
                      Attribute::OptimizeForSize))
-    Threshold = OptSizeUnrollThreshold;
+    Threshold = UP.OptSizeThreshold;
 
   // Find trip count and trip multiple if count is not available
   unsigned TripCount = 0;
@@ -167,11 +180,15 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
     TripCount = SE->getSmallConstantTripCount(L, LatchBlock);
     TripMultiple = SE->getSmallConstantTripMultiple(L, LatchBlock);
   }
+
+  bool Runtime = UnrollRuntime.getNumOccurrences() == 0 ?
+                 UP.Runtime : UnrollRuntime;
+
   // Use a default unroll-count if the user doesn't specify a value
   // and the trip count is a run-time value.  The default is different
   // for run-time or compile-time trip count loops.
-  unsigned Count = CurrentCount;
-  if (UnrollRuntime && CurrentCount == 0 && TripCount == 0)
+  unsigned Count = UserCount ? CurrentCount : UP.Count;
+  if (Runtime && Count == 0 && TripCount == 0)
     Count = UnrollRuntimeCount;
 
   if (Count == 0) {
@@ -204,7 +221,8 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
     if (TripCount != 1 && Size > Threshold) {
       DEBUG(dbgs() << "  Too large to fully unroll with count: " << Count
             << " because size: " << Size << ">" << Threshold << "\n");
-      if (!CurrentAllowPartial && !(UnrollRuntime && TripCount == 0)) {
+      bool AllowPartial = UserAllowPartial ? CurrentAllowPartial : UP.Partial;
+      if (!AllowPartial && !(Runtime && TripCount == 0)) {
         DEBUG(dbgs() << "  will not try to unroll partially because "
               << "-unroll-allow-partial not given\n");
         return false;
@@ -215,7 +233,7 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
         while (Count != 0 && TripCount%Count != 0)
           Count--;
       }
-      else if (UnrollRuntime) {
+      else if (Runtime) {
         // Reduce unroll count to be a lower power-of-two value
         while (Count != 0 && Size > Threshold) {
           Count >>= 1;
@@ -231,7 +249,7 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
   }
 
   // Unroll the loop.
-  if (!UnrollLoop(L, Count, TripCount, UnrollRuntime, TripMultiple, LI, &LPM))
+  if (!UnrollLoop(L, Count, TripCount, Runtime, TripMultiple, LI, &LPM))
     return false;
 
   return true;