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.

llvm-svn: 189565

1 files changed, 17 insertions, 5 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
index 80d060b926e..f8ff275e969 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -55,6 +55,8 @@ namespace {
       CurrentAllowPartial = (P == -1) ? UnrollAllowPartial : (bool)P;
 
       UserThreshold = (T != -1) || (UnrollThreshold.getNumOccurrences() > 0);
+      UserAllowPartial = (P != -1) ||
+                         (UnrollAllowPartial.getNumOccurrences() > 0);
 
       initializeLoopUnrollPass(*PassRegistry::getPassRegistry());
     }
@@ -76,6 +78,7 @@ namespace {
     unsigned CurrentThreshold;
     bool     CurrentAllowPartial;
     bool     UserThreshold;        // CurrentThreshold is user-specified.
+    bool     UserAllowPartial;     // CurrentAllowPartial is user-specified.
 
     bool runOnLoop(Loop *L, LPPassManager &LPM);
 
@@ -145,16 +148,20 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
         << "] Loop %" << Header->getName() << "\n");
   (void)Header;
 
+  TargetTransformInfo::UnrollingPreferences UP;
+  bool HasUP = TTI.getUnrollingPreferences(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 = (HasUP && !UserThreshold) ? UP.Threshold :
+                                                   CurrentThreshold;
   if (!UserThreshold &&
       Header->getParent()->getAttributes().
         hasAttribute(AttributeSet::FunctionIndex,
                      Attribute::OptimizeForSize))
-    Threshold = OptSizeUnrollThreshold;
+    Threshold = HasUP ? UP.OptSizeThreshold : OptSizeUnrollThreshold;
 
   // Find trip count and trip multiple if count is not available
   unsigned TripCount = 0;
@@ -184,6 +191,9 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
     Count = TripCount;
   }
 
+  bool Runtime = (HasUP && UnrollRuntime.getNumOccurrences() == 0) ?
+                 UP.Runtime : UnrollRuntime;
+
   // Enforce the threshold.
   if (Threshold != NoThreshold) {
     unsigned NumInlineCandidates;
@@ -204,7 +214,9 @@ 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 = (HasUP && !UserAllowPartial) ? UP.Partial :
+                                                         CurrentAllowPartial;
+      if (!AllowPartial && !(Runtime && TripCount == 0)) {
         DEBUG(dbgs() << "  will not try to unroll partially because "
               << "-unroll-allow-partial not given\n");
         return false;
@@ -215,7 +227,7 @@ 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 +243,7 @@ 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;