Merge pull request swiftlang#35516 from aschwaighofer/constant_fold_availability

Constant fold known availability checks

Author: aschwaighofer

lib/SILOptimizer/Utils/ConstantFolding.cpp

@@ -1496,6 +1496,38 @@ static bool isApplyOfBuiltin(SILInstruction &I, BuiltinValueKind kind) {
   return false;
 }
 
+static bool isApplyOfKnownAvailability(SILInstruction &I) {
+  auto apply = FullApplySite::isa(&I);
+  if (!apply)
+    return false;
+  auto callee = apply.getReferencedFunctionOrNull();
+  if (!callee)
+    return false;
+  if (!callee->hasSemanticsAttr("availability.osversion"))
+    return false;
+  auto &context = I.getFunction()->getASTContext();
+  auto deploymentAvailability =
+      AvailabilityContext::forDeploymentTarget(context);
+  if (apply.getNumArguments() != 3)
+    return false;
+  auto arg0 = dyn_cast<IntegerLiteralInst>(apply.getArgument(0));
+  if (!arg0)
+    return false;
+  auto arg1 = dyn_cast<IntegerLiteralInst>(apply.getArgument(1));
+  if (!arg1)
+    return false;
+  auto arg2 = dyn_cast<IntegerLiteralInst>(apply.getArgument(2));
+  if (!arg2)
+    return false;
+
+  auto version = VersionRange::allGTE(llvm::VersionTuple(
+      arg0->getValue().getLimitedValue(), arg1->getValue().getLimitedValue(),
+      arg2->getValue().getLimitedValue()));
+
+  auto callAvailability = AvailabilityContext(version);
+  return deploymentAvailability.isContainedIn(callAvailability);
+}
+
 static bool isApplyOfStringConcat(SILInstruction &I) {
   if (auto *AI = dyn_cast<ApplyInst>(&I))
     if (auto *Fn = AI->getReferencedFunctionOrNull())
@@ -1590,6 +1622,11 @@ void ConstantFolder::initializeWorklist(SILFunction &f) {
         continue;
       }
 
+      if (isApplyOfKnownAvailability(*inst)) {
+        WorkList.insert(inst);
+        continue;
+      }
+
       if (isa<CheckedCastBranchInst>(inst) ||
           isa<CheckedCastAddrBranchInst>(inst) ||
           isa<UnconditionalCheckedCastInst>(inst) ||
@@ -1731,6 +1768,19 @@ ConstantFolder::processWorkList() {
           continue;
         }
       }
+    // Replace a known availability.version semantic call.
+    if (isApplyOfKnownAvailability(*I)) {
+      if (auto apply = dyn_cast<ApplyInst>(I)) {
+        SILBuilderWithScope B(I);
+        auto tru = B.createIntegerLiteral(apply->getLoc(), apply->getType(), 1);
+        apply->replaceAllUsesWith(tru);
+        eliminateDeadInstruction(
+            I, [&](SILInstruction *DeadI) { WorkList.remove(DeadI); });
+        WorkList.insert(tru);
+        InvalidateInstructions = true;
+      }
+      continue;
+    }
 
     // If we have a cast instruction, try to optimize it.
     if (isa<CheckedCastBranchInst>(I) || isa<CheckedCastAddrBranchInst>(I) ||

test/SILOptimizer/constant_propagation_availability.swift

@@ -0,0 +1,43 @@
+// RUN: %target-swift-frontend -target x86_64-apple-macos10.15 -emit-sil %s | %FileCheck --check-prefix=CHECK-macosx10_15 %s
+// RUN: %target-swift-frontend -target x86_64-apple-macos10.14 -emit-sil %s | %FileCheck --check-prefix=CHECK-macosx10_14 %s
+// RUN: %target-swift-frontend -O -target x86_64-apple-macos10.15 -emit-sil %s | %FileCheck --check-prefix=CHECK-macosx10_15 %s
+// RUN: %target-swift-frontend -O -target x86_64-apple-macos10.14 -emit-sil %s | %FileCheck --check-prefix=CHECK-macosx10_14 %s
+
+// REQUIRES: OS=macosx
+
+@available(macOS 10.15, *)
+@inline(never)
+public func newFunction() -> Int {
+  return 0
+}
+
+@inline(never)
+public func oldFunction() -> Int {
+  return 1
+}
+
+public func testAvailabilityPropagation() -> Int {
+  if #available(macOS 10.15, *) {
+    return newFunction()
+  } else {
+    return oldFunction()
+  }
+}
+
+// CHECK-macosx10_15-LABEL: sil @$s33constant_propagation_availability27testAvailabilityPropagationSiyF : $@convention(thin) () -> Int {
+// CHECK-macosx10_15-NOT: apply
+// CHECK-macosx10_15:  [[F:%.*]] = function_ref @$s33constant_propagation_availability11newFunctionSiyF
+// CHECK-macosx10_15:  apply [[F]]() : $@convention(thin) () -> Int
+// CHECK-macosx10_15-NOT: apply
+// CHECK-macosx10_15: } // end sil function '$s33constant_propagation_availability27testAvailabilityPropagationSiyF'
+
+// CHECK-macosx10_14-LABEL: sil @$s33constant_propagation_availability27testAvailabilityPropagationSiyF : $@convention(thin) () -> Int {
+// CHECK-macosx10_14:  [[F:%.*]] = function_ref @$ss26_stdlib_isOSVersionAtLeastyBi1_Bw_BwBwtF
+// CHECK-macosx10_14:  apply [[F]]
+// CHECK-macosx10_14:  [[F:%.*]] = function_ref @$s33constant_propagation_availability11newFunctionSiyF
+// CHECK-macosx10_14:  apply [[F]]() : $@convention(thin) () -> Int
+// CHECK-macosx10_14:  [[F:%.*]] = function_ref @$s33constant_propagation_availability11oldFunctionSiyF
+// CHECK-macosx10_14:  apply [[F]]
+// CHECK-macosx10_14: } // end sil function '$s33constant_propagation_availability27testAvailabilityPropagationSiyF'
+
+// CHECK-macosx10_14: sil [readnone] [_semantics "availability.osversion"] @$ss26_stdlib_isOSVersionAtLeastyBi1_Bw_BwBwtF