[NFC] OSSACanonicalizeOwned: Record originals.

When recording a def that's a copy, also record what value it's a copy
of.  This _could_ be rediscovered later, but it's more obvious when done
here.  (A note on rediscovery: it would be equivalent to recursing
through copy_value instructions until finding either (1) some value
which wasn't produced by a copy_value or (2) a copy_value which is the
current def.)

Author: nate-chandler

include/swift/SILOptimizer/Utils/CanonicalizeOSSALifetime.h

@@ -285,6 +285,7 @@ class CanonicalizeOSSALifetime final {
     };
     struct Copy {
       CopyValueInst *cvi;
+      SILValue original;
     };
     struct BorrowedFrom {
       BorrowedFromInst *bfi;
@@ -321,7 +322,9 @@ class CanonicalizeOSSALifetime final {
       return getKind() == rhs.getKind() && getValue() == rhs.getValue();
     }
     static Def root(SILValue value) { return {Root{value}}; }
-    static Def copy(CopyValueInst *cvi) { return {Copy{cvi}}; }
+    static Def copy(CopyValueInst *cvi, SILValue original) {
+      return {Copy{cvi, original}};
+    }
     static Def borrowedFrom(BorrowedFromInst *bfi) {
       return {BorrowedFrom{bfi}};
     }
@@ -339,6 +342,17 @@ class CanonicalizeOSSALifetime final {
       }
       llvm_unreachable("covered switch");
     }
+    SILValue getOriginalValue() const {
+      switch (*this) {
+      case Kind::Copy:
+        return payload.get<Copy>().original;
+      case Kind::Root:
+      case Kind::BorrowedFrom:
+      case Kind::Reborrow:
+        return getValue();
+      }
+      llvm_unreachable("covered switch");
+    }
   };
   friend llvm::DenseMapInfo<Def>;
 

lib/SILOptimizer/Utils/CanonicalizeOSSALifetime.cpp

@@ -165,7 +165,7 @@ bool CanonicalizeOSSALifetime::computeCanonicalLiveness() {
       auto *user = use->getUser();
       // Recurse through copies.
       if (auto *copy = dyn_cast<CopyValueInst>(user)) {
-        addDefToWorklist(Def::copy(copy));
+        addDefToWorklist(Def::copy(copy, def.getOriginalValue()));
         continue;
       }
       if (auto *bfi = dyn_cast<BorrowedFromInst>(user)) {