disable loop interchange, fusion, and unroll-and-jam on runtime assumptions

Author: sebpop

llvm/lib/Transforms/Scalar/LoopFuse.cpp

@@ -1129,7 +1129,11 @@ struct LoopFuser {
         }
       }
     }
-    return true;
+    SCEVUnionPredicate Assumptions = DI.getRuntimeAssumptions();
+    // Fail if the dependence analysis has runtime assumptions.
+    // FIXME: do loop versioning to keep the original loop, and transform the
+    // loop under the runtime assumptions.
+    return Assumptions.isAlwaysTrue();
   }
 
   // Returns true if the instruction \p I can be sunk to the top of the exit
@@ -1172,7 +1176,11 @@ struct LoopFuser {
       }
     }
 
-    return true;
+    SCEVUnionPredicate Assumptions = DI.getRuntimeAssumptions();
+    // Fail if the dependence analysis has runtime assumptions.
+    // FIXME: do loop versioning to keep the original loop, and transform the
+    // loop under the runtime assumptions.
+    return Assumptions.isAlwaysTrue();
   }
 
   /// Collect instructions in the \p FC1 Preheader that can be hoisted
@@ -1420,7 +1428,11 @@ struct LoopFuser {
               return false;
             }
 
-    return true;
+    SCEVUnionPredicate Assumptions = DI.getRuntimeAssumptions();
+    // Fail if the dependence analysis has runtime assumptions.
+    // FIXME: do loop versioning to keep the original loop, and transform the
+    // loop under the runtime assumptions.
+    return Assumptions.isAlwaysTrue();
   }
 
   /// Determine if two fusion candidates are adjacent in the CFG.

llvm/lib/Transforms/Scalar/LoopInterchange.cpp

@@ -220,7 +220,11 @@ static bool populateDependencyMatrix(CharMatrix &DepMatrix, unsigned Level,
     }
   }
 
-  return true;
+  SCEVUnionPredicate Assumptions = DI->getRuntimeAssumptions();
+  // Fail if the dependence analysis has runtime assumptions.
+  // FIXME: do loop versioning to keep the original loop, and transform the
+  // loop under the runtime assumptions.
+  return Assumptions.isAlwaysTrue();
 }
 
 // A loop is moved from index 'from' to an index 'to'. Update the Dependence
@@ -1834,6 +1838,12 @@ PreservedAnalyses LoopInterchangePass::run(LoopNest &LN,
   std::unique_ptr<CacheCost> CC =
       CacheCost::getCacheCost(LN.getOutermostLoop(), AR, DI);
 
+  SCEVUnionPredicate Assumptions = DI.getRuntimeAssumptions();
+  // Early fail when the dependence analysis has runtime assumptions.
+  // FIXME: this could be handled by versioning the loop.
+  if (!Assumptions.isAlwaysTrue())
+    return PreservedAnalyses::all();
+
   if (!LoopInterchange(&AR.SE, &AR.LI, &DI, &AR.DT, CC, &ORE).run(LN))
     return PreservedAnalyses::all();
   U.markLoopNestChanged(true);

llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp

@@ -800,7 +800,12 @@ checkDependencies(Loop &Root, const BasicBlockSet &SubLoopBlocks,
     EarlierLoadsAndStores.append(CurrentLoadsAndStores.begin(),
                                  CurrentLoadsAndStores.end());
   }
-  return true;
+
+  SCEVUnionPredicate Assumptions = DI.getRuntimeAssumptions();
+  // Fail if the dependence analysis has runtime assumptions.
+  // FIXME: do loop versioning to keep the original loop, and transform the
+  // loop under the runtime assumptions.
+  return Assumptions.isAlwaysTrue();
 }
 
 static bool isEligibleLoopForm(const Loop &Root) {