Revert "Revert "Optimizer: improve the load-copy-to-borrow optimization and implement it in swift""

This reverts commit 0666c446ec.

lib/SILOptimizer/PassManager/PassPipeline.cpp

@@ -517,6 +517,7 @@ void addFunctionPasses(SILPassPipelinePlan &P,
     P.addCopyPropagation();
   }
   P.addSemanticARCOpts();
+  P.addLoadCopyToBorrowOptimization();
 
   if (!P.getOptions().EnableOSSAModules) {
     if (P.getOptions().StopOptimizationBeforeLoweringOwnership)
@@ -546,6 +547,7 @@ void addFunctionPasses(SILPassPipelinePlan &P,
       P.addCopyPropagation();
     }
     P.addSemanticARCOpts();
+    P.addLoadCopyToBorrowOptimization();
   }
 
   // Promote stack allocations to values and eliminate redundant
@@ -574,6 +576,7 @@ void addFunctionPasses(SILPassPipelinePlan &P,
   }
   // Optimize copies created during RLE.
   P.addSemanticARCOpts();
+  P.addLoadCopyToBorrowOptimization();
 
   P.addCOWOpts();
   P.addPerformanceConstantPropagation();
@@ -611,6 +614,7 @@ void addFunctionPasses(SILPassPipelinePlan &P,
       P.addCopyPropagation();
     }
     P.addSemanticARCOpts();
+    P.addLoadCopyToBorrowOptimization();
   }
 }
 
@@ -648,6 +652,7 @@ static void addPerfEarlyModulePassPipeline(SILPassPipelinePlan &P) {
     P.addCopyPropagation();
   }
   P.addSemanticARCOpts();
+  P.addLoadCopyToBorrowOptimization();
 
   // Devirtualizes differentiability witnesses into functions that reference them.
   // This unblocks many other passes' optimizations (e.g. inlining) and this is
@@ -994,6 +999,7 @@ SILPassPipelinePlan::getPerformancePassPipeline(const SILOptions &Options) {
       P.addCopyPropagation();
     }
     P.addSemanticARCOpts();
+    P.addLoadCopyToBorrowOptimization();
   }
 
   P.addCrossModuleOptimization();