Merge pull request #59665 from eeckstein/target-constprop

eeckstein · web-flow · commit ba42be5fcf2d · 2022-06-24T08:57:54.000+02:00
SILOptimizer: add a pass to perform target specific constant folding.
diff --git a/include/swift/AST/SILGenRequests.h b/include/swift/AST/SILGenRequests.h
@@ -29,6 +29,7 @@ class LangOptions;
 class ModuleDecl;
 class SILModule;
 class SILOptions;
+class IRGenOptions;
 
 namespace Lowering {
   class TypeConverter;
@@ -47,6 +48,7 @@ struct ASTLoweringDescriptor {
   llvm::PointerUnion<FileUnit *, ModuleDecl *> context;
   Lowering::TypeConverter &conv;
   const SILOptions &opts;
+  const IRGenOptions *irgenOptions;
 
   /// A specific set of SILDeclRefs to emit. If set, only these refs will be
   /// emitted. Otherwise the entire \c context will be emitted.
@@ -74,15 +76,17 @@ struct ASTLoweringDescriptor {
 public:
   static ASTLoweringDescriptor
   forFile(FileUnit &sf, Lowering::TypeConverter &conv, const SILOptions &opts,
-          Optional<SILRefsToEmit> refsToEmit = None) {
-    return ASTLoweringDescriptor{&sf, conv, opts, refsToEmit};
+          Optional<SILRefsToEmit> refsToEmit = None,
+          const IRGenOptions *irgenOptions = nullptr) {
+    return ASTLoweringDescriptor{&sf, conv, opts, irgenOptions, refsToEmit};
   }
 
   static ASTLoweringDescriptor
   forWholeModule(ModuleDecl *mod, Lowering::TypeConverter &conv,
                  const SILOptions &opts,
-                 Optional<SILRefsToEmit> refsToEmit = None) {
-    return ASTLoweringDescriptor{mod, conv, opts, refsToEmit};
+                 Optional<SILRefsToEmit> refsToEmit = None,
+                 const IRGenOptions *irgenOptions = nullptr) {
+    return ASTLoweringDescriptor{mod, conv, opts, irgenOptions, refsToEmit};
   }
 
   /// Retrieves the files to generate SIL for. If the descriptor is configured
diff --git a/include/swift/SIL/SILModule.h b/include/swift/SIL/SILModule.h
@@ -103,6 +103,7 @@ class AnyFunctionType;
 class ASTContext;
 class FileUnit;
 class FuncDecl;
+class IRGenOptions;
 class KeyPathPattern;
 class ModuleDecl;
 class SILUndef;
@@ -353,6 +354,12 @@ class SILModule {
   /// The options passed into this SILModule.
   const SILOptions &Options;
 
+  /// IRGen options to be used by target specific SIL optimization passes.
+  ///
+  /// Not null, if the module is created by the compiler itself (and not
+  /// e.g. by lldb).
+  const IRGenOptions *irgenOptions;
+
   /// The number of functions created in this module, which will be the index of
   /// the next function.
   unsigned nextFunctionIndex = 0;
@@ -382,7 +389,8 @@ class SILModule {
 #endif
 
   SILModule(llvm::PointerUnion<FileUnit *, ModuleDecl *> context,
-            Lowering::TypeConverter &TC, const SILOptions &Options);
+            Lowering::TypeConverter &TC, const SILOptions &Options,
+            const IRGenOptions *irgenOptions = nullptr);
 
   SILModule(const SILModule&) = delete;
   void operator=(const SILModule&) = delete;
@@ -537,7 +545,8 @@ class SILModule {
   /// single-file mode, and a ModuleDecl in whole-module mode.
   static std::unique_ptr<SILModule>
   createEmptyModule(llvm::PointerUnion<FileUnit *, ModuleDecl *> context,
-                    Lowering::TypeConverter &TC, const SILOptions &Options);
+                    Lowering::TypeConverter &TC, const SILOptions &Options,
+                    const IRGenOptions *irgenOptions = nullptr);
 
   /// Get the Swift module associated with this SIL module.
   ModuleDecl *getSwiftModule() const { return TheSwiftModule; }
@@ -570,6 +579,7 @@ class SILModule {
   bool isOptimizedOnoneSupportModule() const;
 
   const SILOptions &getOptions() const { return Options; }
+  const IRGenOptions *getIRGenOptionsOrNull() const { return irgenOptions; }
 
   using iterator = FunctionListType::iterator;
   using const_iterator = FunctionListType::const_iterator;
diff --git a/include/swift/SILOptimizer/PassManager/Passes.def b/include/swift/SILOptimizer/PassManager/Passes.def
@@ -356,6 +356,8 @@ PASS(ReleaseHoisting, "release-hoisting",
      "SIL release Hoisting")
 PASS(LateReleaseHoisting, "late-release-hoisting",
      "Late SIL release Hoisting Preserving Epilogues")
+PASS(TargetConstantFolding, "target-constant-folding",
+     "Target specific constant folding")
 IRGEN_PASS(LoadableByAddress, "loadable-address",
      "SIL Large Loadable type by-address lowering.")
 PASS(MandatorySILLinker, "mandatory-linker",
diff --git a/include/swift/Subsystems.h b/include/swift/Subsystems.h
@@ -179,12 +179,14 @@ namespace swift {
   /// SIL of all files in the module is present in the SILModule.
   std::unique_ptr<SILModule>
   performASTLowering(ModuleDecl *M, Lowering::TypeConverter &TC,
-                     const SILOptions &options);
+                     const SILOptions &options,
+                     const IRGenOptions *irgenOptions = nullptr);
 
   /// Turn a source file into SIL IR.
   std::unique_ptr<SILModule>
   performASTLowering(FileUnit &SF, Lowering::TypeConverter &TC,
-                     const SILOptions &options);
+                     const SILOptions &options,
+                     const IRGenOptions *irgenOptions = nullptr);
 
   using ModuleOrSourceFile = PointerUnion<ModuleDecl *, SourceFile *>;
 
diff --git a/lib/FrontendTool/FrontendTool.cpp b/lib/FrontendTool/FrontendTool.cpp
@@ -766,7 +766,9 @@ bool swift::performCompileStepsPostSema(CompilerInstance &Instance,
     const PrimarySpecificPaths PSPs =
         Instance.getPrimarySpecificPathsForWholeModuleOptimizationMode();
     SILOptions SILOpts = getSILOptions(PSPs);
-    auto SM = performASTLowering(mod, Instance.getSILTypes(), SILOpts);
+    IRGenOptions irgenOpts = Invocation.getIRGenOptions();
+    auto SM = performASTLowering(mod, Instance.getSILTypes(), SILOpts,
+                                 &irgenOpts);
     return performCompileStepsPostSILGen(Instance, std::move(SM), mod, PSPs,
                                          ReturnValue, observer);
   }
@@ -779,8 +781,9 @@ bool swift::performCompileStepsPostSema(CompilerInstance &Instance,
       const PrimarySpecificPaths PSPs =
           Instance.getPrimarySpecificPathsForSourceFile(*PrimaryFile);
       SILOptions SILOpts = getSILOptions(PSPs);
+    IRGenOptions irgenOpts = Invocation.getIRGenOptions();
       auto SM = performASTLowering(*PrimaryFile, Instance.getSILTypes(),
-                                   SILOpts);
+                                   SILOpts, &irgenOpts);
       result |= performCompileStepsPostSILGen(Instance, std::move(SM),
                                               PrimaryFile, PSPs, ReturnValue,
                                               observer);
diff --git a/lib/IRGen/CMakeLists.txt b/lib/IRGen/CMakeLists.txt
@@ -57,6 +57,7 @@ add_swift_host_library(swiftIRGen STATIC
   Outlining.cpp
   StructLayout.cpp
   SwiftTargetInfo.cpp
+  TargetConstantFolding.cpp
   TypeLayout.cpp
   TypeLayoutDumper.cpp
   TypeLayoutVerifier.cpp
diff --git a/lib/IRGen/IRGen.cpp b/lib/IRGen/IRGen.cpp
@@ -1059,7 +1059,7 @@ GeneratedModule IRGenRequest::evaluate(Evaluator &evaluator,
   auto SILMod = std::unique_ptr<SILModule>(desc.SILMod);
   if (!SILMod) {
     auto loweringDesc = ASTLoweringDescriptor{
-        desc.Ctx, desc.Conv, desc.SILOpts,
+        desc.Ctx, desc.Conv, desc.SILOpts, nullptr,
         symsToEmit.map([](const auto &x) { return x.silRefsToEmit; })};
     SILMod = llvm::cantFail(Ctx.evaluator(LoweredSILRequest{loweringDesc}));
 
diff --git a/lib/IRGen/TargetConstantFolding.cpp b/lib/IRGen/TargetConstantFolding.cpp
@@ -0,0 +1,142 @@
+//===--- TargetConstantFolding.cpp ----------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2022 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+// This pass lowers loadable SILTypes. On completion, the SILType of every
+// function argument is an address instead of the type itself.
+// This reduces the code size.
+// Consequently, this pass is required for IRGen.
+// It is a mandatory IRGen preparation pass (not a diagnostic pass).
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "target-constant-folding"
+#include "IRGenModule.h"
+#include "swift/SIL/SILBuilder.h"
+#include "swift/SILOptimizer/PassManager/Transforms.h"
+#include "swift/SILOptimizer/Utils/InstructionDeleter.h"
+#include "llvm/Support/Debug.h"
+
+using namespace swift;
+using namespace swift::irgen;
+
+namespace {
+
+/// Performs constant folding for target-specific values.
+///
+/// Specifically, this optimization constant folds
+/// ```
+///   MemoryLayout<S>.size
+///   MemoryLayout<S>.alignment
+///   MemoryLayout<S>.stride
+/// ```
+/// Constant folding those expressions in the middle of the SIL pipeline
+/// enables other optimizations to e.g. allow such expressions in statically
+/// allocated global variables (done by the GlobalOpt pass).
+class TargetConstantFolding : public SILModuleTransform {
+private:
+  /// The entry point to the transformation.
+  void run() override {
+    auto *irgenOpts = getModule()->getIRGenOptionsOrNull();
+    if (!irgenOpts)
+      return;
+    
+    // We need an IRGenModule to get the actual sizes from type lowering.
+    // Creating an IRGenModule involves some effort. Therefore this is a
+    // module pass rather than a function pass so that this one-time setup
+    // only needs to be done once and not for all functions in a module.
+    IRGenerator irgen(*irgenOpts, *getModule());
+    auto targetMachine = irgen.createTargetMachine();
+    if (!targetMachine)
+      return;
+    IRGenModule IGM(irgen, std::move(targetMachine));
+
+    // Scan all instructions in the module for constant foldable instructions.
+    for (SILFunction &function : *getModule()) {
+    
+      if (!function.shouldOptimize())
+        continue;
+    
+      bool changed = false;
+      for (SILBasicBlock &block : function) {
+        InstructionDeleter deleter;
+
+        for (SILInstruction *inst : deleter.updatingRange(&block)) {
+          if (constFold(inst, IGM)) {
+            deleter.forceDelete(inst);
+            changed = true;
+          }
+        }
+        deleter.cleanupDeadInstructions();
+      }
+      if (changed) {
+        invalidateAnalysis(&function, SILAnalysis::InvalidationKind::Instructions);
+      }
+    }
+  }
+ 
+  /// Constant fold a single instruction.
+  ///
+  /// Returns true if `inst` was replaced and can be deleted.
+  bool constFold(SILInstruction *inst, IRGenModule &IGM) {
+    auto *bi = dyn_cast<BuiltinInst>(inst);
+    if (!bi)
+      return false;
+    
+    llvm::Constant *c = nullptr;
+    uint64_t offset = 0;
+
+    switch (bi->getBuiltinInfo().ID) {
+      case BuiltinValueKind::Sizeof:
+        c = getTypeInfoOfBuiltin(bi, IGM).getStaticSize(IGM);
+        break;
+      case BuiltinValueKind::Alignof:
+        c = getTypeInfoOfBuiltin(bi, IGM).getStaticAlignmentMask(IGM);
+        // The constant is the alignment _mask_. We get the actual alignment by
+        // adding 1.
+        offset = 1;
+        break;
+      case BuiltinValueKind::Strideof:
+        c = getTypeInfoOfBuiltin(bi, IGM).getStaticStride(IGM);
+        break;
+      default:
+        return false;
+    }
+    auto *intConst = dyn_cast_or_null<llvm::ConstantInt>(c);
+    if (!intConst)
+      return false;
+
+    APInt value = intConst->getValue();
+    value += APInt(value.getBitWidth(), offset);
+    auto intTy = bi->getType().getAs<BuiltinIntegerType>();
+    if (!intTy)
+      return false;
+
+    value = value.sextOrTrunc(intTy->getGreatestWidth());
+
+    // Replace the builtin by an integer literal.
+    SILBuilderWithScope builder(bi);
+    auto *intLit = builder.createIntegerLiteral(bi->getLoc(), bi->getType(),
+                                                value);
+    bi->replaceAllUsesWith(intLit);
+    return true;
+  }
+
+  const TypeInfo &getTypeInfoOfBuiltin(BuiltinInst *bi, IRGenModule &IGM) {
+    SubstitutionMap subs = bi->getSubstitutions();
+    SILType lowered = IGM.getLoweredType(subs.getReplacementTypes()[0]);
+    return IGM.getTypeInfo(lowered);
+  }
+};
+
+} // end anonymous namespace
+
+SILTransform *swift::createTargetConstantFolding() {
+  return new TargetConstantFolding();
+}
diff --git a/lib/SIL/IR/SILModule.cpp b/lib/SIL/IR/SILModule.cpp
@@ -90,9 +90,11 @@ class SILModule::SerializationCallback final
 };
 
 SILModule::SILModule(llvm::PointerUnion<FileUnit *, ModuleDecl *> context,
-                     Lowering::TypeConverter &TC, const SILOptions &Options)
+                     Lowering::TypeConverter &TC, const SILOptions &Options,
+                     const IRGenOptions *irgenOptions)
     : Stage(SILStage::Raw), loweredAddresses(!Options.EnableSILOpaqueValues),
-      indexTrieRoot(new IndexTrieNode()), Options(Options), serialized(false),
+      indexTrieRoot(new IndexTrieNode()), Options(Options),
+      irgenOptions(irgenOptions), serialized(false),
       regDeserializationNotificationHandlerForNonTransparentFuncOME(false),
       regDeserializationNotificationHandlerForAllFuncOME(false),
       prespecializedFunctionDeclsImported(false), SerializeSILAction(),
@@ -203,8 +205,10 @@ void SILModule::checkForLeaksAfterDestruction() {
 
 std::unique_ptr<SILModule> SILModule::createEmptyModule(
     llvm::PointerUnion<FileUnit *, ModuleDecl *> context,
-    Lowering::TypeConverter &TC, const SILOptions &Options) {
-  return std::unique_ptr<SILModule>(new SILModule(context, TC, Options));
+    Lowering::TypeConverter &TC, const SILOptions &Options,
+    const IRGenOptions *irgenOptions) {
+  return std::unique_ptr<SILModule>(new SILModule(context, TC, Options,
+                                                  irgenOptions));
 }
 
 ASTContext &SILModule::getASTContext() const {
diff --git a/lib/SILGen/SILGen.cpp b/lib/SILGen/SILGen.cpp
@@ -2243,7 +2243,7 @@ ASTLoweringRequest::evaluate(Evaluator &evaluator,
   SILInstruction::resetInstructionCounts();
 
   auto silMod = SILModule::createEmptyModule(desc.context, desc.conv,
-                                             desc.opts);
+                                             desc.opts, desc.irgenOptions);
 
   // If all function bodies are being skipped there's no reason to do any
   // SIL generation.
@@ -2285,15 +2285,18 @@ ASTLoweringRequest::evaluate(Evaluator &evaluator,
 
 std::unique_ptr<SILModule>
 swift::performASTLowering(ModuleDecl *mod, Lowering::TypeConverter &tc,
-                          const SILOptions &options) {
-  auto desc = ASTLoweringDescriptor::forWholeModule(mod, tc, options);
+                          const SILOptions &options,
+                          const IRGenOptions *irgenOptions) {
+  auto desc = ASTLoweringDescriptor::forWholeModule(mod, tc, options,
+                                                    None, irgenOptions);
   return llvm::cantFail(
       mod->getASTContext().evaluator(ASTLoweringRequest{desc}));
 }
 
 std::unique_ptr<SILModule>
 swift::performASTLowering(FileUnit &sf, Lowering::TypeConverter &tc,
-                          const SILOptions &options) {
-  auto desc = ASTLoweringDescriptor::forFile(sf, tc, options);
+                          const SILOptions &options,
+                          const IRGenOptions *irgenOptions) {
+  auto desc = ASTLoweringDescriptor::forFile(sf, tc, options, None, irgenOptions);
   return llvm::cantFail(sf.getASTContext().evaluator(ASTLoweringRequest{desc}));
 }
diff --git a/lib/SILOptimizer/PassManager/PassPipeline.cpp b/lib/SILOptimizer/PassManager/PassPipeline.cpp
@@ -666,6 +666,7 @@ static void addMidLevelFunctionPipeline(SILPassPipelinePlan &P) {
 static void addClosureSpecializePassPipeline(SILPassPipelinePlan &P) {
   P.startPipeline("ClosureSpecialize");
   P.addDeadFunctionAndGlobalElimination();
+  P.addTargetConstantFolding();
   P.addDeadStoreElimination();
   P.addDeadObjectElimination();
 
diff --git a/test/SILOptimizer/devirt_protocol_method_invocations.swift b/test/SILOptimizer/devirt_protocol_method_invocations.swift
@@ -138,9 +138,8 @@ public func test_devirt_protocol_extension_method_invocation_with_self_return_ty
 // CHECK:   return [[T1]]
 
 // CHECK: sil @$s34devirt_protocol_method_invocations14testExMetatypeSiyF
-// CHECK:   [[T0:%.*]] = builtin "sizeof"<Int>
-// CHECK:   [[T1:%.*]] = builtin {{.*}}([[T0]]
-// CHECK:   [[T2:%.*]] = struct $Int ([[T1]] : {{.*}})
+// CHECK:   [[T0:%.*]] = integer_literal
+// CHECK:   [[T2:%.*]] = struct $Int ([[T0]] : {{.*}})
 // CHECK:   return [[T2]] : $Int
 
 @inline(never)
diff --git a/test/SILOptimizer/target-const-prop.swift b/test/SILOptimizer/target-const-prop.swift
