SIL Verifier: don't run read-only access scope verification in lowered SIL

LoadableByAddress in lowered SIL can insert `copy_addr`s inside read-only access scope.

rdar://163248403

Author: eeckstein

SwiftCompilerSources/Sources/SIL/Utilities/Verifier.swift

@@ -156,15 +156,20 @@ extension LoadBorrowInst : VerifiableInstruction {
 
 extension BeginAccessInst : VerifiableInstruction {
   func verify(_ context: VerifierContext) {
-    if context.silStage == .raw {
-      return
-    }
     // Catch violations like
     // ```
     //   %1 = begin_access [read] %0
     //   store %2 to %0
     //   end_access %1
     // ```
+
+    guard context.silStage == .canonical else {
+      // Mandatory passes on raw SIL need to be completed until we can verify this.
+      // Also, LoadableByAddress in lowered SIL can insert `copy_addr`s inside read-only access scope.
+      // Therefore we can only run this verification in canonical SIL.
+      return
+    }
+
     if address.type.isMoveOnly && enforcement == .static {
       // This is a workaround for a bug in the move-only checker: rdar://151841926.
       // The move-only checker sometimes inserts destroy_addr within read-only static access scopes.

test/SIL/verifier-fail-access-scope.sil

@@ -0,0 +1,17 @@
+// RUN: not --crash %target-sil-opt %s -o /dev/null
+
+// REQUIRES: asserts
+
+sil_stage canonical
+
+import Builtin
+import Swift
+
+sil [ossa] @write_in_read_only_scope : $@convention(thin) (@inout Int, Int) -> () {
+bb0(%0 : $*Int, %1 : $Int):
+  %2 = begin_access [read] [static] %0
+  store %1 to [trivial] %0
+  end_access %2
+  %5 = tuple()
+  return %5
+}

test/SIL/verifier-no-fail-access-scope1.sil

@@ -0,0 +1,19 @@
+// RUN: %target-sil-opt %s -o /dev/null
+
+// REQUIRES: asserts
+
+sil_stage raw
+
+// Need to complete mandatory passes until we can verify that there are no stores in read-only access scopes.
+
+import Builtin
+import Swift
+
+sil [ossa] @write_in_read_only_scope : $@convention(thin) (@inout Int, Int) -> () {
+bb0(%0 : $*Int, %1 : $Int):
+  %2 = begin_access [read] [static] %0
+  store %1 to [trivial] %0
+  end_access %2
+  %5 = tuple()
+  return %5
+}

test/SIL/verifier-no-fail-access-scope2.sil

@@ -0,0 +1,19 @@
+// RUN: %target-sil-opt %s -o /dev/null
+
+// REQUIRES: asserts
+
+sil_stage lowered
+
+// LoadableByAddress in lowered SIL can insert copy_addrs inside read-only access scope.
+
+import Builtin
+import Swift
+
+sil [ossa] @write_in_read_only_scope : $@convention(thin) (@inout Int, Int) -> () {
+bb0(%0 : $*Int, %1 : $Int):
+  %2 = begin_access [read] [static] %0
+  store %1 to [trivial] %0
+  end_access %2
+  %5 = tuple()
+  return %5
+}