Merge pull request #40517 from nate-chandler/cherrypick/lexical-lifetimes/enable-with-copy-propagation/release/5.6

[5.6] Copy-propagation enables lexical-lifetimes.

Author: nate-chandler

include/swift/AST/DiagnosticsFrontend.def

@@ -80,6 +80,8 @@ ERROR(error_unknown_arg,none,
       "unknown argument: '%0'", (StringRef))
 ERROR(error_invalid_arg_value,none,
       "invalid value '%1' in '%0'", (StringRef, StringRef))
+ERROR(error_invalid_arg_combination,none,
+      "unsupported argument combination: '%0' and '%1'", (StringRef, StringRef))
 WARNING(warning_invalid_locale_code,none,
       "unsupported locale code; supported locale codes are: '%0'", (StringRef))
 WARNING(warning_locale_path_not_found,none,

include/swift/AST/SILOptions.h

@@ -31,15 +31,31 @@
 namespace swift {
 
 enum class LexicalLifetimesOption : uint8_t {
-  // Do not insert any lexical lifetimes.
+  // Do not insert lexical markers.
   Off = 0,
 
-  // Insert lexical lifetimes in SILGen, but remove them before leaving Raw SIL.
-  Early,
+  // Insert lexical markers via lexical borrow scopes and the lexical flag on
+  // alloc_stacks produced from alloc_boxes, but strip them when lowering out of
+  // Raw SIL.
+  DiagnosticMarkersOnly,
 
-  // Insert lexical lifetimes and do not remove them until OSSA is lowered. This
-  // is experimental.
-  ExperimentalLate,
+  // Insert lexical markers and use them to lengthen object lifetime based on
+  // lexical scope.
+  On,
+};
+
+enum class CopyPropagationOption : uint8_t {
+  // Do not add any copy propagation passes.
+  Off = 0,
+
+  // Only add the copy propagation passes requested by other flags, currently
+  // just -enable-ossa-modules.
+  RequestedPassesOnly,
+
+  // Add all relevant copy propagation passes.  If a setting, e.g.
+  // -enable-ossa-modules, requests to add copy propagation to the pipeline, do
+  // so.
+  On
 };
 
 class SILModule;
@@ -59,17 +75,15 @@ class SILOptions {
   bool RemoveRuntimeAsserts = false;
 
   /// Enable experimental support for emitting defined borrow scopes.
-  LexicalLifetimesOption LexicalLifetimes = LexicalLifetimesOption::Early;
-
-  /// Force-run SIL copy propagation to shorten object lifetime in whatever
-  /// optimization pipeline is currently used.
-  /// When this is 'false' the pipeline has default behavior.
-  bool EnableCopyPropagation = false;
+  LexicalLifetimesOption LexicalLifetimes =
+      LexicalLifetimesOption::DiagnosticMarkersOnly;
 
-  /// Disable SIL copy propagation to preserve object lifetime in whatever
+  /// Whether to run SIL copy propagation to shorten object lifetime in whatever
   /// optimization pipeline is currently used.
-  /// When this is 'false' the pipeline has default behavior.
-  bool DisableCopyPropagation = false;
+  ///
+  /// When this is 'RequestedPassesOnly' the pipeline has default behavior.
+  CopyPropagationOption CopyPropagation =
+      CopyPropagationOption::RequestedPassesOnly;
 
   /// Controls whether the SIL ARC optimizations are run.
   bool EnableARCOptimizations = true;

include/swift/Option/FrontendOptions.td

@@ -213,9 +213,12 @@ def dependency_scan_cache_remarks : Flag<["-"], "Rdependency-scan-cache">,
   HelpText<"Emit remarks indicating use of the serialized module dependency scanning cache.">;
 
 def enable_copy_propagation : Flag<["-"], "enable-copy-propagation">,
-  HelpText<"Run SIL copy propagation to shorten object lifetime.">;
-def disable_copy_propagation : Flag<["-"], "disable-copy-propagation">,
-  HelpText<"Don't run SIL copy propagation to preserve object lifetime.">;
+  HelpText<"Run SIL copy propagation with lexical lifetimes to shorten object "
+           "lifetimes while preserving variable lifetimes.">;
+def copy_propagation_state_EQ :
+  Joined<["-"], "enable-copy-propagation=">,
+  HelpText<"Whether to enable copy propagation">,
+  MetaVarName<"true|requested-passes-only|false">;
 
 def enable_infer_public_concurrent_value : Flag<["-"], "enable-infer-public-sendable">,
     HelpText<"Enable inference of Sendable conformances for public structs and enums">;
@@ -259,15 +262,18 @@ def enable_experimental_concurrency :
   Flag<["-"], "enable-experimental-concurrency">,
   HelpText<"Enable experimental concurrency model">;
 
-def disable_lexical_lifetimes :
-  Flag<["-"], "disable-lexical-lifetimes">,
-  HelpText<"Disables early lexical lifetimes. Mutually exclusive with "
-           "-enable-lexical-lifetimes">;
-
+def enable_lexical_borrow_scopes :
+  Joined<["-"], "enable-lexical-borrow-scopes=">,
+  HelpText<"Whether to emit lexical borrow scopes (default: true)">,
+  MetaVarName<"true|false">;
+          
 def enable_lexical_lifetimes :
+  Joined<["-"], "enable-lexical-lifetimes=">,
+  HelpText<"Whether to enable lexical lifetimes">,
+  MetaVarName<"true|false">;
+def enable_lexical_lifetimes_noArg :
   Flag<["-"], "enable-lexical-lifetimes">,
-  HelpText<"Enable lexical lifetimes. Mutually exclusive with "
-           "-disable-lexical-lifetimes">;
+  HelpText<"Enable lexical lifetimes">;
 
 def enable_experimental_move_only :
   Flag<["-"], "enable-experimental-move-only">,

include/swift/SIL/OwnershipUtils.h

@@ -104,12 +104,9 @@ inline bool isForwardingConsume(SILValue value) {
 bool findInnerTransitiveGuaranteedUses(
     SILValue guaranteedValue, SmallVectorImpl<Operand *> *usePoints = nullptr);
 
-/// Like findInnerTransitiveGuaranteedUses except that rather than it being a
-/// precondition that the provided value not be a BorrowedValue, it is a [type-
-/// system-enforced] precondition that the provided value be a BorrowedValue.
-///
-/// TODO: Merge with findInnerTransitiveGuaranteedUses.
-bool findInnerTransitiveGuaranteedUsesOfBorrowedValue(
+/// Find all uses in the extended lifetime (i.e. including copies) of a simple
+/// (i.e. not reborrowed) borrow scope and its transitive uses.
+bool findExtendedUsesOfSimpleBorrowedValue(
     BorrowedValue borrowedValue,
     SmallVectorImpl<Operand *> *usePoints = nullptr);
 
@@ -566,8 +563,11 @@ struct BorrowedValue {
   /// This ignores reborrows. The assumption is that, since \p uses are
   /// dominated by this local scope, checking the extended borrow scope should
   /// not be necessary to determine they are within the scope.
+  ///
+  /// \p deadEndBlocks is optional during transition. It will be completely
+  /// removed in an upcoming commit.
   bool areUsesWithinLocalScope(ArrayRef<Operand *> uses,
-                               DeadEndBlocks &deadEndBlocks) const;
+                               DeadEndBlocks *deadEndBlocks) const;
 
   /// Given a local borrow scope introducer, visit all non-forwarding consuming
   /// users. This means that this looks through guaranteed block arguments. \p
@@ -1206,6 +1206,14 @@ void visitTransitiveEndBorrows(
     BorrowedValue beginBorrow,
     function_ref<void(EndBorrowInst *)> visitEndBorrow);
 
+/// Whether the specified lexical begin_borrow instruction is nested.
+///
+/// A begin_borrow [lexical] is nested if the borrowed value's lifetime is
+/// guaranteed by another lexical scope.  That happens if:
+/// - the value is a guaranteed argument to the function
+/// - the value is itself a begin_borrow [lexical]
+bool isNestedLexicalBeginBorrow(BeginBorrowInst *bbi);
+
 } // namespace swift
 
 #endif

include/swift/SIL/PrunedLiveness.h

@@ -334,8 +334,9 @@ class PrunedLiveness {
   /// client already knows that inst occurs after the start of liveness.
   bool isWithinBoundary(SILInstruction *inst) const;
 
+  /// \p deadEndBlocks is optional.
   bool areUsesWithinBoundary(ArrayRef<Operand *> uses,
-                             DeadEndBlocks &deadEndBlocks) const;
+                             DeadEndBlocks *deadEndBlocks) const;
 
   /// Compute liveness for a single SSA definition.
   void computeSSALiveness(SILValue def);

include/swift/SIL/SILModule.h

@@ -911,14 +911,17 @@ inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, const SILModule &M){
 inline bool SILOptions::supportsLexicalLifetimes(const SILModule &mod) const {
   switch (mod.getStage()) {
   case SILStage::Raw:
-    // In Raw SIL, we support lexical lifetimes as long as lexical lifetimes is
-    // not turned off all the way. This means lexical lifetimes is set to either
-    // early or experimental late.
+    // In raw SIL, lexical markers are used for diagnostics.  These markers are
+    // present as long as the lexical lifetimes feature is not disabled
+    // entirely.
     return LexicalLifetimes != LexicalLifetimesOption::Off;
   case SILStage::Canonical:
-    // In Canonical SIL, we only support lexical lifetimes when in experimental
-    // late mode.
-    return LexicalLifetimes == LexicalLifetimesOption::ExperimentalLate;
+    // In Canonical SIL, lexical markers are used to ensure that object
+    // lifetimes do not get observably shortened from the end of a lexical
+    // scope.  That behavior only occurs when lexical lifetimes is (fully)
+    // enabled.  (When only diagnostic markers are enabled, the markers are
+    // stripped as part of lowering from raw to canonical SIL.)
+    return LexicalLifetimes == LexicalLifetimesOption::On;
   case SILStage::Lowered:
     // We do not support OSSA in Lowered SIL, so this is always false.
     return false;

include/swift/SIL/SILValue.h

@@ -438,7 +438,7 @@ class ValueBase : public SILNode, public SILAllocated<ValueBase> {
 
   template <class T> inline T *getSingleConsumingUserOfType() const;
 
-  /// Returns true if this operand has exactly two.
+  /// Returns true if this operand has exactly two uses.
   ///
   /// This is useful if one has found a predefined set of 2 unique users and
   /// wants to check if there are any other users without iterating over the

include/swift/SILOptimizer/Utils/CanonicalizeBorrowScope.h

@@ -147,7 +147,9 @@ class CanonicalizeBorrowScope {
   bool consolidateBorrowScope();
 };
 
-bool shrinkBorrowScope(BeginBorrowInst *bbi, InstructionDeleter &deleter);
+bool shrinkBorrowScope(
+    BeginBorrowInst *bbi, InstructionDeleter &deleter,
+    SmallVectorImpl<CopyValueInst *> &modifiedCopyValueInsts);
 
 } // namespace swift
 

lib/Frontend/CompilerInvocation.cpp

@@ -1455,25 +1455,131 @@ static bool ParseSILArgs(SILOptions &Opts, ArgList &Args,
   // -Ounchecked might also set removal of runtime asserts (cond_fail).
   Opts.RemoveRuntimeAsserts |= Args.hasArg(OPT_RemoveRuntimeAsserts);
 
-  // If experimental move only is enabled, always enable lexical lifetime as
-  // well. Move only depends on lexical lifetimes.
-  bool enableExperimentalLexicalLifetimes =
-      Args.hasArg(OPT_enable_lexical_lifetimes) ||
-      Args.hasArg(OPT_enable_experimental_move_only);
-  // Error if both experimental lexical lifetimes and disable lexical lifetimes
-  // are both set.
-  if (enableExperimentalLexicalLifetimes &&
-      Args.hasArg(OPT_disable_lexical_lifetimes)) {
+  Optional<CopyPropagationOption> specifiedCopyPropagationOption;
+  if (Arg *A = Args.getLastArg(OPT_copy_propagation_state_EQ)) {
+    specifiedCopyPropagationOption =
+        llvm::StringSwitch<Optional<CopyPropagationOption>>(A->getValue())
+            .Case("true", CopyPropagationOption::On)
+            .Case("false", CopyPropagationOption::Off)
+            .Case("requested-passes-only",
+                  CopyPropagationOption::RequestedPassesOnly)
+            .Default(None);
+  }
+  if (Args.hasArg(OPT_enable_copy_propagation)) {
+    if (specifiedCopyPropagationOption) {
+      if (*specifiedCopyPropagationOption == CopyPropagationOption::Off) {
+        // Error if copy propagation has been set to ::Off via the meta-var form
+        // and enabled via the flag.
+        Diags.diagnose(SourceLoc(), diag::error_invalid_arg_combination,
+                       "enable-copy-propagation",
+                       "enable-copy-propagation=false");
+        return true;
+      } else if (*specifiedCopyPropagationOption ==
+                 CopyPropagationOption::RequestedPassesOnly) {
+        // Error if copy propagation has been set to ::RequestedPassesOnly via
+        // the meta-var form and enabled via the flag.
+        Diags.diagnose(SourceLoc(), diag::error_invalid_arg_combination,
+                       "enable-copy-propagation",
+                       "enable-copy-propagation=requested-passes-only");
+        return true;
+      }
+    } else {
+      specifiedCopyPropagationOption = CopyPropagationOption::On;
+    }
+  }
+  if (specifiedCopyPropagationOption) {
+    Opts.CopyPropagation = *specifiedCopyPropagationOption;
+  }
+
+  Optional<bool> enableLexicalBorrowScopesFlag;
+  if (Arg *A = Args.getLastArg(OPT_enable_lexical_borrow_scopes)) {
+    enableLexicalBorrowScopesFlag =
+        llvm::StringSwitch<Optional<bool>>(A->getValue())
+            .Case("true", true)
+            .Case("false", false)
+            .Default(None);
+  }
+  Optional<bool> enableLexicalLifetimesFlag;
+  if (Arg *A = Args.getLastArg(OPT_enable_lexical_lifetimes)) {
+    enableLexicalLifetimesFlag =
+        llvm::StringSwitch<Optional<bool>>(A->getValue())
+            .Case("true", true)
+            .Case("false", false)
+            .Default(None);
+  }
+  if (Args.getLastArg(OPT_enable_lexical_lifetimes_noArg)) {
+    if (!enableLexicalLifetimesFlag.getValueOr(true)) {
+      // Error if lexical lifetimes have been disabled via the meta-var form
+      // and enabled via the flag.
+      Diags.diagnose(SourceLoc(), diag::error_invalid_arg_combination,
+                     "enable-lexical-lifetimes",
+                     "enable-lexical-lifetimes=false");
+      return true;
+    } else {
+      enableLexicalLifetimesFlag = true;
+    }
+  }
+
+  if (enableLexicalLifetimesFlag.getValueOr(false) &&
+      !enableLexicalBorrowScopesFlag.getValueOr(true)) {
+    // Error if lexical lifetimes have been enabled but lexical borrow scopes--
+    // on which they are dependent--have been disabled.
+    Diags.diagnose(SourceLoc(), diag::error_invalid_arg_combination,
+                   "enable-lexical-lifetimes=true",
+                   "enable-lexical-borrow-scopes=false");
     return true;
-  } else {
-    if (enableExperimentalLexicalLifetimes)
-      Opts.LexicalLifetimes = LexicalLifetimesOption::ExperimentalLate;
-    if (Args.hasArg(OPT_disable_lexical_lifetimes))
+  }
+
+  if (Args.hasArg(OPT_enable_experimental_move_only) &&
+      !enableLexicalBorrowScopesFlag.getValueOr(true)) {
+    // Error if move-only is enabled and lexical borrow scopes--on which it
+    // depends--has been disabled.
+    Diags.diagnose(SourceLoc(), diag::error_invalid_arg_combination,
+                   "enable-experimental-move-only",
+                   "enable-lexical-borrow-scopes=false");
+    return true;
+  }
+
+  if (Args.hasArg(OPT_enable_experimental_move_only) &&
+      !enableLexicalLifetimesFlag.getValueOr(true)) {
+    // Error if move-only is enabled and lexical lifetimes--on which it
+    // depends--has been disabled.
+    Diags.diagnose(SourceLoc(), diag::error_invalid_arg_combination,
+                   "enable-experimental-move-only",
+                   "enable-lexical-lifetimes=false");
+    return true;
+  }
+
+  // Unless overridden below, enabling copy propagation means enabling lexical
+  // lifetimes.
+  if (Opts.CopyPropagation == CopyPropagationOption::On)
+    Opts.LexicalLifetimes = LexicalLifetimesOption::On;
+
+  // Unless overridden below, disable copy propagation means disabling lexical
+  // lifetimes.
+  if (Opts.CopyPropagation == CopyPropagationOption::Off)
+    Opts.LexicalLifetimes = LexicalLifetimesOption::DiagnosticMarkersOnly;
+
+  // If move-only is enabled, always enable lexical lifetime as well.  Move-only
+  // depends on lexical lifetimes.
+  if (Args.hasArg(OPT_enable_experimental_move_only))
+    Opts.LexicalLifetimes = LexicalLifetimesOption::On;
+
+  if (enableLexicalLifetimesFlag) {
+    if (*enableLexicalLifetimesFlag) {
+      Opts.LexicalLifetimes = LexicalLifetimesOption::On;
+    } else {
+      Opts.LexicalLifetimes = LexicalLifetimesOption::DiagnosticMarkersOnly;
+    }
+  }
+  if (enableLexicalBorrowScopesFlag) {
+    if (*enableLexicalBorrowScopesFlag) {
+      Opts.LexicalLifetimes = LexicalLifetimesOption::DiagnosticMarkersOnly;
+    } else {
       Opts.LexicalLifetimes = LexicalLifetimesOption::Off;
+    }
   }
 
-  Opts.EnableCopyPropagation |= Args.hasArg(OPT_enable_copy_propagation);
-  Opts.DisableCopyPropagation |= Args.hasArg(OPT_disable_copy_propagation);
   Opts.EnableARCOptimizations &= !Args.hasArg(OPT_disable_arc_opts);
   Opts.EnableOSSAModules |= Args.hasArg(OPT_enable_ossa_modules);
   Opts.EnableOSSAOptimizations &= !Args.hasArg(OPT_disable_ossa_opts);

lib/IRGen/AllocStackHoisting.cpp

@@ -118,7 +118,8 @@ insertDeallocStackAtEndOf(SmallVectorImpl<SILInstruction *> &FunctionExits,
   // Insert dealloc_stack in the exit blocks.
   for (auto *Exit : FunctionExits) {
     SILBuilderWithScope Builder(Exit);
-    Builder.createDeallocStack(AllocStack->getLoc(), AllocStack);
+    Builder.createDeallocStack(CleanupLocation(AllocStack->getLoc()),
+                               AllocStack);
   }
 }