Manual merge 2020/10/08

.github/workflows/main.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Free disk space
         run: |
           df -h
-          sudo apt-get purge libgcc-9-dev gcc-9 libstdc++-9-dev
+          sudo apt-get purge libgcc-9-dev gcc-9 libstdc++-9-dev clang-6.0 llvm-6.0
           sudo swapoff -a
           sudo rm -f /swapfile
           sudo rm -rf /opt/hostedtoolcache

apinotes/os.apinotes

@@ -63,5 +63,5 @@ Functions:
   SwiftPrivate: true
   NullabilityOfRet: O
 - Name: _os_signpost_emit_with_name_impl
-  Availability: nonswift
-  AvailabilityMsg: 'Use os_signpost'
+  SwiftPrivate: true
+  NullabilityOfRet: O

docs/DebuggingTheCompiler.md

@@ -30,6 +30,8 @@ benefit of all Swift developers.
         - [Debugging the Compiler using advanced LLDB Breakpoints](#debugging-the-compiler-using-advanced-lldb-breakpoints)
         - [Debugging the Compiler using LLDB Scripts](#debugging-the-compiler-using-lldb-scripts)
         - [Custom LLDB Commands](#custom-lldb-commands)
+    - [Debugging at LLVM Level](#debugging-at-llvm-level)
+        - [Options for Dumping LLVM IR](#options-for-dumping-llvm-ir)
     - [Bisecting Compiler Errors](#bisecting-compiler-errors)
         - [Bisecting on SIL optimizer pass counts to identify optimizer bugs](#bisecting-on-sil-optimizer-pass-counts-to-identify-optimizer-bugs)
         - [Using git-bisect in the presence of branch forwarding/feature branches](#using-git-bisect-in-the-presence-of-branch-forwardingfeature-branches)
@@ -537,6 +539,20 @@ to define custom commands using just other lldb commands. For example,
 
     (lldb) command alias cs sequence p/x $rax; stepi
 
+## Debugging at LLVM Level
+
+### Options for Dumping LLVM IR
+
+Similar to SIL, one can configure LLVM to dump the llvm-ir at various points in
+the pipeline. Here is a quick summary of the various options:
+
+* ``-Xllvm -print-before=$PASS_ID``: Print the LLVM IR before a specified LLVM pass runs.
+* ``-Xllvm -print-before-all``: Print the LLVM IR before each pass runs.
+* ``-Xllvm -print-after-all``: Print the LLVM IR after each pass runs.
+* ``-Xllvm -filter-print-funcs=$FUNC_NAME_1,$FUNC_NAME_2,...,$FUNC_NAME_N``:
+  When printing IR for functions for print-[before|after]-all options, Only
+  print the IR for functions whose name is in this comma separated list.
+
 ## Bisecting Compiler Errors
 
 ### Bisecting on SIL optimizer pass counts to identify optimizer bugs

docs/RequestEvaluator.md

@@ -80,4 +80,4 @@ The request-evaluator is relatively new to the Swift compiler, having been intro
 * Port higher-level queries (e.g., those that come from SourceKit) over to the request-evaluator, so we can see the dependencies of a given SourceKit request for testing and performance tuning.
 
 ## Prior art
-Rust's compiler went through a similar transformation to support [demand-driven compilation](https://rust-lang-nursery.github.io/rustc-guide/query.html). We should learn from their experience!
+Rust's compiler went through a similar transformation to support [demand-driven compilation](https://rustc-dev-guide.rust-lang.org/query.html). We should learn from their experience!

include/swift/AST/ASTContext.h

@@ -694,6 +694,9 @@ class ASTContext final {
   /// generic metadata.
   AvailabilityContext getIntermodulePrespecializedGenericMetadataAvailability();
 
+  /// Get the runtime availability of support for concurrency.
+  AvailabilityContext getConcurrencyAvailability();
+
   /// Get the runtime availability of features introduced in the Swift 5.2
   /// compiler for the target platform.
   AvailabilityContext getSwift52Availability();