[AutoDiff] Fix forward-mode differentiation ownership verification failure. (swiftlang#33898)

Previously, `LinearMapInfo::shouldDifferentiateInstruction` had a special case
for `copy_value`, returning true for `copy_value` instructions with an active
operand.

This is unexpected and led to "leaked owned value" ownership verification
failures due to unnecessarily cloned `copy_value` instructions during
differential generation.

Now, the special case is removed, fixing the failures.
`shouldDifferentiateInstruction` returns true for `copy_value` instructions
whose operand and result are both active.

Resolves SR-13530.

Author: dan-zheng

lib/SILOptimizer/Differentiation/LinearMapInfo.cpp

@@ -537,10 +537,6 @@ bool LinearMapInfo::shouldDifferentiateInstruction(SILInstruction *inst) {
         isa<EndBorrowInst>(inst) || isa<DeallocationInst>(inst) ||
         isa<DestroyValueInst>(inst) || isa<DestroyAddrInst>(inst))
       return true;
-    // Should differentiate any instruction that creates an SSA copy of an
-    // active operand.
-    if (isa<CopyValueInst>(inst))
-      return true;
   }
   return false;
 }

test/AutoDiff/validation-test/forward_mode_simple.swift

@@ -1389,4 +1389,15 @@ ForwardModeTests.test("ApplyNonActiveIndirectResult") {
   expectEqual(1.0, derivative(at: 2, in: applyNonactiveArgumentActiveIndirectResult))
 }
 
+ForwardModeTests.test("SR-13530") {
+  // SR-13530: Test "leaked owned value" ownership verification failure related
+  // to differential generation for `copy_value` instruction.
+  @differentiable
+  func SR_13530(_ x: NonresilientTracked<Float>) -> NonresilientTracked<Float> {
+    precondition(x >= 0)
+    return x
+  }
+  expectEqual(1, derivative(at: 2, in: SR_13530))
+}
+
 runAllTests()