The patch refactors unroll pass.

Summary:
Unroll factor (Count) calculations moved to a new function.
Early exits on pragma and "-unroll-count" defined factor added.
New type of unrolling "Force" introduced (previously used implicitly).
New unroll preference "AllowRemainder" introduced and set "true" by default.
(should be set to false for architectures that suffers from it).

Reviewers: hfinkel, mzolotukhin, zzheng

Differential Revision: http://reviews.llvm.org/D19553

From: Evgeny Stupachenko <evstupac@gmail.com>
llvm-svn: 271071

1 files changed, 7 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index 77314d70903..baeaab17c11 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -199,7 +199,7 @@ static bool needToInsertPhisForLCSSA(Loop *L, std::vector<BasicBlock *> Blocks,
 ///
 /// This utility preserves LoopInfo. It will also preserve ScalarEvolution and
 /// DominatorTree if they are non-null.
-bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
+bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount, bool Force,
                       bool AllowRuntime, bool AllowExpensiveTripCount,
                       unsigned TripMultiple, LoopInfo *LI, ScalarEvolution *SE,
                       DominatorTree *DT, AssumptionCache *AC,
@@ -298,8 +298,12 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
   if (RuntimeTripCount && TripMultiple % Count != 0 &&
       !UnrollRuntimeLoopRemainder(L, Count, AllowExpensiveTripCount,
                                   UnrollRuntimeEpilog, LI, SE, DT, 
-                                  PreserveLCSSA))
-    return false;
+                                  PreserveLCSSA)) {
+    if (Force)
+      RuntimeTripCount = false;
+    else
+      return false;
+  }
 
   // Notify ScalarEvolution that the loop will be substantially changed,
   // if not outright eliminated.