SILVerifier - allow rebind_memory token to cross functions

Remove a completely unnecessary assertion to handle reasonable use
cases.

Author: atrick

lib/SIL/Utils/MemAccessUtils.cpp

@@ -2387,6 +2387,7 @@ void swift::visitAccessedAddress(SILInstruction *I,
   case SILInstructionKind::EndCOWMutationInst:
   case SILInstructionKind::BeginUnpairedAccessInst:
   case SILInstructionKind::BindMemoryInst:
+  case SILInstructionKind::RebindMemoryInst:
   case SILInstructionKind::CheckedCastValueBranchInst:
   case SILInstructionKind::CondFailInst:
   case SILInstructionKind::CopyBlockInst:

lib/SIL/Verifier/SILVerifier.cpp

@@ -3046,9 +3046,6 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
     requireSameType(rbi->getInToken()->getType(),
                     SILType::getBuiltinWordType(F.getASTContext()),
                     "rebind_memory token must be a Builtin.Int64");
-    require(isa<BindMemoryInst>(rbi->getInToken())
-            || isa<RebindMemoryInst>(rbi->getInToken()),
-            "rebind_memory token must originate from bind_memory");
   }
 
   void checkIndexAddrInst(IndexAddrInst *IAI) {

test/SILOptimizer/pointer_conversion.swift

@@ -1,6 +1,8 @@
-// RUN: %target-swift-frontend -emit-sil -O %s | %FileCheck %s
+// RUN: %target-swift-frontend -parse-stdlib -parse-as-library -emit-sil -O %s | %FileCheck %s
 // REQUIRES: optimized_stdlib,swift_stdlib_no_asserts
 
+import Swift
+
 // Opaque, unoptimizable functions to call.
 @_silgen_name("takesConstRawPointer")
 func takesConstRawPointer(_ x: UnsafeRawPointer)
@@ -99,3 +101,23 @@ public func arrayLiteralPromotion() {
   // CHECK: apply [[FN]]([[PTR]])
 }
 
+// Test sil verification at -O with bind_memory and rebind_memory
+// where the rebind is in a defer block.
+//
+// CHECK-LABEL: sil @$s18pointer_conversion21testWithMemoryRebound6rawPtr2to8capacity_q_Bp_xmSiq_SPyxGKXEtKr0_lF
+// CHECK: [[BIND:%.*]] = bind_memory %1 : $Builtin.RawPointer, %{{.*}} : $Builtin.Word to $*T
+// CHECK: rebind_memory %1 : $Builtin.RawPointer to [[BIND]] : $Builtin.Word
+// CHECK-LABEL: } // end sil function '$s18pointer_conversion21testWithMemoryRebound6rawPtr2to8capacity_q_Bp_xmSiq_SPyxGKXEtKr0_lF'
+public func testWithMemoryRebound<T, Result>(
+  rawPtr: Builtin.RawPointer,
+  to type: T.Type,
+  capacity count: Int,
+  _ body: (_ pointer: UnsafePointer<T>) throws -> Result
+) rethrows -> Result {
+  let binding =
+    Builtin.bindMemory(rawPtr, count._builtinWordValue, T.self)
+  defer {
+    Builtin.rebindMemory(rawPtr, binding)
+  }
+  return try body(.init(rawPtr))
+}