EscapeAnalysis: Invert defer edges for array semantics.

Defer edges should always point to the more specific SSA value. For
example, the contents of a memory location point to the values stored
in that locations. Tuples point to their elements. BBArgs point to
their source operands. Likewise, array objects should point to their
exposed unsafe pointer (which is effectively a value stored in the
array object). I'm not sure why the defer edges were reversed in the
first place, but it was always confusing me.

Author: atrick

lib/SILOptimizer/Analysis/EscapeAnalysis.cpp

@@ -1891,7 +1891,7 @@ void EscapeAnalysis::analyzeInstruction(SILInstruction *I,
           if (LoadedElement) {
             if (CGNode *arrayElementStorage =
                     ConGraph->getFieldContent(ArrayObjNode)) {
-              ConGraph->defer(LoadedElement, arrayElementStorage);
+              ConGraph->defer(arrayElementStorage, LoadedElement);
               return;
             }
           }
@@ -1902,7 +1902,7 @@ void EscapeAnalysis::analyzeInstruction(SILInstruction *I,
         // returned address point to the same element storage.
         if (CGNode *ArrayObjNode = ConGraph->getValueContent(ASC.getSelf())) {
           CGNode *arrayElementAddress = ConGraph->getNode(ASC.getCallResult());
-          ConGraph->defer(arrayElementAddress, ArrayObjNode);
+          ConGraph->defer(ArrayObjNode, arrayElementAddress);
           return;
         }
         break;

test/SILOptimizer/escape_analysis.sil

@@ -1212,10 +1212,10 @@ bb0(%0 : $Array<X>):
 
 // CHECK-LABEL: CG of arraysemantics_get_element
 // CHECK-NEXT:    Arg %0 Esc: A, Succ: (%0.1)
-// CHECK-NEXT:    Con [ref] %0.1 Esc: A, Succ: %1.2
+// CHECK-NEXT:    Con [ref] %0.1 Esc: A, Succ:
 // CHECK-NEXT:    Arg [ref] %1 Esc: A, Succ: (%1.1)
 // CHECK-NEXT:    Con [int] %1.1 Esc: A, Succ: (%1.2)
-// CHECK-NEXT:    Con %1.2 Esc: A, Succ: 
+// CHECK-NEXT:    Con %1.2 Esc: A, Succ: %0.1
 // CHECK-NEXT:  End
 sil @arraysemantics_get_element : $@convention(thin) (Array<X>) -> @out X {
 bb0(%io : $*X, %1 : $Array<X>):
@@ -1246,9 +1246,9 @@ bb0(%0 : $*Array<X>):
 
 // CHECK-LABEL: CG of arraysemantics_get_element_address
 // CHECK-NEXT:    Arg [ref] %0 Esc: A, Succ: (%0.1)
-// CHECK-NEXT:    Con [int] %0.1 Esc: A, Succ: 
+// CHECK-NEXT:    Con [int] %0.1 Esc: A, Succ: (%0.2), %4
 // CHECK-NEXT:    Con %0.2 Esc: A, Succ: 
-// CHECK-NEXT:    Val %4 Esc: , Succ: %0.1
+// CHECK-NEXT:    Val %4 Esc: A, Succ: (%0.2)
 // CHECK-NEXT:  End
 sil @arraysemantics_get_element_address : $@convention(thin) (Array<X>) -> () {
 bb0(%0 : $Array<X>):