Improve LifetimeDependence.Scope for mutable trivial variables.

Recognize dependence on the address of a trivial 'var' as an "access" dependence
instead of an "unknown" dependence. This allows the mark_dependence to be
resolved as "[nonescaping]".

Author: atrick

SwiftCompilerSources/Sources/Optimizer/Utilities/LifetimeDependenceUtils.swift

@@ -394,6 +394,8 @@ extension LifetimeDependence.Scope {
       self = .borrowed(BeginBorrowValue(bbi)!)
     case is MoveValueInst:
       self = .owned(introducer)
+    case let bai as BeginAccessInst:
+      self = .access(bai)
     default:
       self = .unknown(introducer)
     }

test/SILGen/addressors.swift

@@ -46,6 +46,7 @@ struct A {
 // CHECK:   [[BASE:%.*]] = load [[T0]] : $*UnsafeMutablePointer<Int32>
 // CHECK:   return [[BASE]] : $UnsafeMutablePointer<Int32>
 
+// SILGEN-LABEL: sil hidden [ossa] @$s10addressors5test0yyF : $@convention(thin) () -> () {
 // CHECK-LABEL: sil hidden @$s10addressors5test0yyF : $@convention(thin) () -> () {
 func test0() {
 // CHECK: [[A:%.*]] = alloc_stack [var_decl] $A
@@ -55,12 +56,16 @@ func test0() {
 // CHECK: store [[AVAL]] to [[A]]
   var a = A()
 
-// CHECK: [[ACCESS:%.*]] = begin_access [read] [static] [[A]] : $*A
+// SILGEN: [[ACCESS:%.*]] = begin_access [read] [unknown] %{{.*}} : $*A
+// SILGEN: [[LD:%.*]] = load [trivial] [[ACCESS]] : $*A
+// SILGEN: [[T3:%.*]] = pointer_to_address %{{.*}} : $Builtin.RawPointer to [strict] $*Int32
+// SILGEN: [[MD:%.*]] = mark_dependence [unresolved] [[T3]] : $*Int32 on [[LD]] : $A
+
 // CHECK: [[T0:%.*]] = function_ref @$s10addressors1AVys5Int32VAEcilu :
 // CHECK: [[T1:%.*]] = apply [[T0]]({{%.*}}, [[AVAL]])
 // CHECK: [[T2:%.*]] = struct_extract [[T1]] : $UnsafePointer<Int32>, #UnsafePointer._rawValue
 // CHECK: [[T3:%.*]] = pointer_to_address [[T2]] : $Builtin.RawPointer to [strict] $*Int32
-// CHECK: [[MD:%.*]] = mark_dependence [nonescaping] [[T3]] : $*Int32 on [[ACCESS]] : $*A
+// CHECK: [[MD:%.*]] = mark_dependence [nonescaping] [[T3]] : $*Int32 on [[AVAL]] : $A
 // CHECK: [[ACCESS:%.*]] = begin_access [read] [unsafe] [[MD]] : $*Int32
 // CHECK: [[Z:%.*]] = load [[ACCESS]] : $*Int32
   let z = a[10]

test/SILOptimizer/lifetime_dependence/lifetime_dependence_scope_fixup.swift

@@ -231,7 +231,7 @@ public func test10() {
 // CHECK-LABEL: sil hidden @$s31lifetime_dependence_scope_fixup37testPointeeDependenceOnMutablePointer1pySPys5Int64VG_tF : $@convention(thin) (UnsafePointer<Int64>) -> () {
 // CHECK: bb0(%0 : $UnsafePointer<Int64>):
 // CHECK:   [[ALLOC:%.*]] = alloc_stack [var_decl] $UnsafePointer<Int64>, var, name "ptr", type $UnsafePointer<Int64>
-// CHECK:   mark_dependence %{{.*}} on %0
+// CHECK:   mark_dependence [nonescaping] %{{.*}} on %0
 // CHECK-LABEL: } // end sil function '$s31lifetime_dependence_scope_fixup37testPointeeDependenceOnMutablePointer1pySPys5Int64VG_tF'
 func testPointeeDependenceOnMutablePointer(p: UnsafePointer<Int64>) {
   var ptr = p

test/SILOptimizer/lifetime_dependence/scopefixup.sil

@@ -91,9 +91,11 @@ sil @pointeeAddressor : $@convention(method) <τ_0_0 where τ_0_0 : ~Copyable> (
 // CHECK: bb0(%0 : $UnsafePointer<Int64>):
 // CHECK:   [[ACCESS:%.*]] = begin_access [read] [unknown]
 // CHECK:   [[LD:%.*]] = load [trivial] [[ACCESS]]
-// CHECK:   end_access [[ACCESS]]
 // CHECK:   [[ADR:%.*]] = pointer_to_address %{{.*}} to [strict] $*Int64
-// CHECK:   mark_dependence [unresolved] [[ADR]] on [[LD]]
+// CHECK:   [[MD:%.*]] = mark_dependence [unresolved] [[ADR]] on [[LD]]
+// CHECK:   [[ACCESS2:%.*]] = begin_access [read] [unsafe] [[MD]]
+// CHECK:   end_access [[ACCESS2]]
+// CHECK:   end_access [[ACCESS]]
 // CHECK-LABEL: } // end sil function 'testTrivialAccess'
 sil hidden [ossa] @testTrivialAccess : $@convention(thin) (UnsafePointer<Int64>) -> () {
 bb0(%0 : $UnsafePointer<Int64>):

test/SILOptimizer/unsafeAddress.swift

@@ -97,13 +97,11 @@ func testSMod(s: inout S) {
 
 // Accessing s.data causes an escaping dependence because we don't extend the local access scope of 's'.
 //
-// TODO: could we notice the local access is already nested inside the same kind of access (modify) and consider this to
-// be 'mark_dependence [nonescaping]'?
-//
 // CHECK-LABEL: sil hidden @$s4main16testSInoutBorrow5mut_syAA1SVz_tF : $@convention(thin) (@inout S) -> () {
 // CHECK: [[ACCESS:%.*]] = begin_access [read] [static] %0
+// CHECK: [[LD:%.*]] = load [[ACCESS]]
 // CHECK: [[ADR:%.*]] = pointer_to_address %{{.*}} to [strict] $*NC
-// CHECK: [[MD:%.*]] = mark_dependence [[ADR]] on [[ACCESS]]
+// CHECK: [[MD:%.*]] = mark_dependence [nonescaping] [[ADR]] on [[LD]]
 // CHECK: begin_access [read] [unsafe] [[MD]]
 // CHECK: apply
 // CHECK: end_access
@@ -114,8 +112,9 @@ func testSInoutBorrow(mut_s s: inout S) {
 
 // CHECK-LABEL: sil hidden @$s4main19testSInoutMutBorrow5mut_syAA1SVz_tF : $@convention(thin) (@inout S) -> () {
 // CHECK: [[ACCESS:%.*]] = begin_access [read] [static] %0
+// CHECK: [[LD:%.*]] = load [[ACCESS]]
 // CHECK: [[ADR:%.*]] = pointer_to_address %{{.*}} to [strict] $*NC
-// CHECK: [[MD:%.*]] = mark_dependence [nonescaping] [[ADR]] on [[ACCESS]]
+// CHECK: [[MD:%.*]] = mark_dependence [nonescaping] [[ADR]] on [[LD]]
 // CHECK: begin_access [read] [unsafe] [[MD]]
 // CHECK: apply
 // CHECK: end_access