From 703d89c8bd92cc44b181897e0a3b816ae8ef04ac Mon Sep 17 00:00:00 2001
From: Slava Pestov <spestov@apple.com>
Date: Thu, 31 Mar 2022 11:26:07 -0400
Subject: [PATCH] Turn off the GenericSignatureBuilder

The Requirement Machine has been enabled in 'verify' mode for a while,
where we run both the GenericSignatureBuilder and Requirement Machine
minimization algorithm and compare the results, with the
GenericSignatureBuilder being used to emit diagnostics.

Now, it's time to flip the flags to 'enabled' mode, where the
GenericSignatureBuilder doesn't run at all, and the Requirement Machine
emits diagnostics. This finally allows us to realize the correctness
and performance gains from using the Requirement Machine.

See https://forums.swift.org/t/the-requirement-machine-a-new-generics-implementation-based-on-term-rewriting/55601/9
for details.

Correctness:

- https://bugs.swift.org/browse/SR-7353
- https://bugs.swift.org/browse/SR-9595
- https://bugs.swift.org/browse/SR-10532
- https://bugs.swift.org/browse/SR-10752
- https://bugs.swift.org/browse/SR-11100
- https://bugs.swift.org/browse/SR-11532
- https://bugs.swift.org/browse/SR-11997
- https://bugs.swift.org/browse/SR-12120
- https://bugs.swift.org/browse/SR-12736
- https://bugs.swift.org/browse/SR-12980
- https://bugs.swift.org/browse/SR-13018
- https://bugs.swift.org/browse/SR-13491
- https://bugs.swift.org/browse/SR-13502
- https://bugs.swift.org/browse/SR-14484
- https://bugs.swift.org/browse/SR-14485
- https://bugs.swift.org/browse/SR-14659
- https://bugs.swift.org/browse/SR-14776
- https://bugs.swift.org/browse/SR-14917
- https://bugs.swift.org/browse/SR-15009
- https://bugs.swift.org/browse/SR-15790
- https://bugs.swift.org/browse/SR-15920
- rdar://25065503
- rdar://39225307
- rdar://44590919
- rdar://45957015
- rdar://50169558
- rdar://51068593
- rdar://52921168
- rdar://54394068
- rdar://55758433
- rdar://58455439
- rdar://59132837
- rdar://62894047
- rdar://64953119
- rdar://65015626
- rdar://65558829
- rdar://68084643
- rdar://68376692
- rdar://75329340
- rdar://76646764
- rdar://77683844
- rdar://77794156
- rdar://78233378
- rdar://78481510
- rdar://78643612
- rdar://80820294
- rdar://81276358
- rdar://81425392
- rdar://83308672
- rdar://83373331
- rdar://83848546
- rdar://83955123
- rdar://88514540
- rdar://89641532
- rdar://90264856
- rdar://90343419

Performance:

- rdar://33654588
- rdar://47821930
- rdar://51908331
- rdar://59037195
- rdar://65131776
- rdar://73771235
- rdar://75188696

GSB crashes with no reduced test case that are likely fixed:

- https://bugs.swift.org/browse/SR-4872
- rdar://32144681
- rdar://42376632
- rdar://46270030
- rdar://47199993
- rdar://48648900
- rdar://49535930
- rdar://49712445
- rdar://49712637
- rdar://49713096
- rdar://49713107
- rdar://60334839
- rdar://66593156
- rdar://68982368
- rdar://76706682
- rdar://77794745
- rdar://84724541
---
 include/swift/Basic/LangOptions.h      | 4 ++--
 stdlib/cmake/modules/SwiftSource.cmake | 5 -----
 2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/include/swift/Basic/LangOptions.h b/include/swift/Basic/LangOptions.h
index d9d90eda3d4b7..0c8fa84984a64 100644
--- a/include/swift/Basic/LangOptions.h
+++ b/include/swift/Basic/LangOptions.h
@@ -528,7 +528,7 @@ namespace swift {
     /// Enable the new experimental protocol requirement signature minimization
     /// algorithm.
     RequirementMachineMode RequirementMachineProtocolSignatures =
-        RequirementMachineMode::Verify;
+        RequirementMachineMode::Enabled;
 
     /// Enable the new experimental generic signature minimization algorithm
     /// for abstract generic signatures.
@@ -538,7 +538,7 @@ namespace swift {
     /// Enable the new experimental generic signature minimization algorithm
     /// for user-written generic signatures.
     RequirementMachineMode RequirementMachineInferredSignatures =
-        RequirementMachineMode::Verify;
+        RequirementMachineMode::Enabled;
 
     /// Enable preprocessing pass to eliminate conformance requirements
     /// on generic parameters which are made concrete. Usually you want this
diff --git a/stdlib/cmake/modules/SwiftSource.cmake b/stdlib/cmake/modules/SwiftSource.cmake
index 128ddde624ca7..903214b874cae 100644
--- a/stdlib/cmake/modules/SwiftSource.cmake
+++ b/stdlib/cmake/modules/SwiftSource.cmake
@@ -469,11 +469,6 @@ function(_compile_swift_files
     endif()
   endif()
 
-  # The standard library and overlays are built with the Requirement Machine enabled.
-  if(SWIFTFILE_IS_STDLIB)
-    list(APPEND swift_flags "-Xfrontend" "-requirement-machine-inferred-signatures=verify")
-  endif()
-
   # The standard library and overlays are built resiliently when SWIFT_STDLIB_STABLE_ABI=On.
   if(SWIFTFILE_IS_STDLIB AND SWIFT_STDLIB_STABLE_ABI)
     list(APPEND swift_flags "-enable-library-evolution")