Merge pull request swiftlang#77752 from DougGregor/perf-diag-check-throws

[Performance diagnostics] Enable checking of throw instructions

Author: DougGregor

include/swift/SILOptimizer/Utils/BasicBlockOptUtils.h

@@ -69,20 +69,6 @@ class ReachingReturnBlocks {
   }
 };
 
-/// Computes the set of blocks which are not used for error handling, i.e. not
-/// (exclusively) reachable from the error-block of a try_apply.
-class NonErrorHandlingBlocks {
-    BasicBlockWorklist worklist;
-
-public:
-  NonErrorHandlingBlocks(SILFunction *function);
-
-  /// Returns true if there exists a path from \p block to the return-block.
-  bool isNonErrorHandling(SILBasicBlock *block) const {
-    return worklist.isVisited(block);
-  }
-};
-
 /// Remove all unreachable blocks in a function.
 bool removeUnreachableBlocks(SILFunction &f);
 

lib/SILOptimizer/Mandatory/PerformanceDiagnostics.cpp

@@ -213,8 +213,6 @@ bool PerformanceDiagnostics::visitFunctionEmbeddedSwift(
     return false;
   visitedFuncs[function] = PerformanceConstraints::None;
 
-  NonErrorHandlingBlocks neBlocks(function);
-
   for (SILBasicBlock &block : *function) {
     for (SILInstruction &inst : block) {
       if (visitInst(&inst, PerformanceConstraints::None, parentLoc)) {
@@ -283,28 +281,11 @@ bool PerformanceDiagnostics::visitFunction(SILFunction *function,
   if (!function->isDefinition())
     return false;
 
-  NonErrorHandlingBlocks neBlocks(function);
-
   for (SILBasicBlock &block : *function) {
     // Exclude fatal-error blocks.
     if (isa<UnreachableInst>(block.getTerminator()))
       continue;
 
-    // TODO: it's not yet clear how to deal with error existentials.
-    // Ignore them for now. If we have typed throws we could ban error existentials
-    // because typed throws would provide and alternative.
-    if (isa<ThrowInst>(block.getTerminator()))
-      continue;
-
-    // If a function has multiple throws, all throw-path branch to the single throw-block.
-    if (SILBasicBlock *succ = block.getSingleSuccessorBlock()) {
-      if (isa<ThrowInst>(succ->getTerminator()))
-        continue;
-    }
-
-    if (!neBlocks.isNonErrorHandling(&block))
-      continue;
-
     for (SILInstruction &inst : block) {
       if (visitInst(&inst, perfConstr, parentLoc)) {
         if (inst.getLoc().getSourceLoc().isInvalid()) {

lib/SILOptimizer/Utils/BasicBlockOptUtils.cpp

@@ -55,19 +55,6 @@ ReachingReturnBlocks::ReachingReturnBlocks(SILFunction *function)
   }
 }
 
-NonErrorHandlingBlocks::NonErrorHandlingBlocks(SILFunction *function)
-    : worklist(function->getEntryBlock()) {
-  while (SILBasicBlock *block = worklist.pop()) {
-    if (auto ta = dyn_cast<TryApplyInst>(block->getTerminator())) {
-      worklist.pushIfNotVisited(ta->getNormalBB());
-    } else {
-      for (SILBasicBlock *succ : block->getSuccessorBlocks()) {
-        worklist.pushIfNotVisited(succ);
-      }
-    }
-  }
-}
-
 bool swift::removeUnreachableBlocks(SILFunction &f) {
   ReachableBlocks reachable(&f);
   // Visit all the blocks without doing any extra work.

test/SILOptimizer/performance-annotations.swift

@@ -101,13 +101,22 @@ func errorExistential(_ b: Bool) throws -> Int {
   if b {
     return 28
   }
-  throw MyError()
+  throw MyError() // expected-error{{Using type 'MyError' can cause metadata allocation or locks}}
+}
+
+@_noLocks
+func concreteThrowsExistential(_ b: Bool) throws -> Int {
+  if b {
+    return 28
+  }
+
+  throw ErrorEnum.tryAgain // expected-error{{Using type 'any Error' can cause metadata allocation or locks}}
 }
 
 @_noLocks
 func multipleThrows(_ b1: Bool, _ b2: Bool) throws -> Int {
   if b1 {
-    throw MyError()
+    throw MyError() // expected-error{{Using type 'MyError' can cause metadata allocation or locks}}
   }
   if b2 {
     throw MyError2()
@@ -119,7 +128,7 @@ func multipleThrows(_ b1: Bool, _ b2: Bool) throws -> Int {
 func testCatch(_ b: Bool) throws -> Int? {
   do {
     return try errorExistential(true)
-  } catch let e as MyError {
+  } catch let e as MyError { // expected-error{{this code performs reference counting operations which can cause locking}}
     print(e)
     return nil
   }