[Coverage] Handle non-local exits out of DoStmt's properly

First, assign counter expressions to the DoStmt and its body. Next,
fix the count associated to the DoStmt when handling a non-local exit.

This fixes SR-1850.

Author: vedantk

lib/SILGen/SILGenProfiling.cpp

@@ -349,7 +349,8 @@ struct CoverageMapping : public ASTWalker {
     CounterExpr *JumpsToLabel = nullptr;
     Stmt *ParentStmt = Parent.getAsStmt();
     if (ParentStmt) {
-      if (isa<DoCatchStmt>(ParentStmt) || isa<CatchStmt>(ParentStmt))
+      if (isa<DoStmt>(ParentStmt) || isa<DoCatchStmt>(ParentStmt) ||
+          isa<CatchStmt>(ParentStmt))
         return;
       if (auto *LS = dyn_cast<LabeledStmt>(ParentStmt))
         JumpsToLabel = &getCounter(LS);
@@ -530,6 +531,10 @@ struct CoverageMapping : public ASTWalker {
     } else if (isa<CaseStmt>(S)) {
       pushRegion(S);
 
+    } else if (auto *DS = dyn_cast<DoStmt>(S)) {
+      assignCounter(DS->getBody(), CounterExpr::Ref(getCurrentCounter()));
+      assignCounter(DS);
+
     } else if (auto *DCS = dyn_cast<DoCatchStmt>(S)) {
       assignCounter(DCS->getBody(), CounterExpr::Ref(getCurrentCounter()));
       assignCounter(DCS);

test/SILGen/coverage_label.swift

@@ -0,0 +1,25 @@
+// RUN: %target-swift-frontend -Xllvm -sil-full-demangle -suppress-warnings -profile-generate -profile-coverage-mapping -emit-sorted-sil -emit-sil -module-name coverage_label %s | FileCheck %s
+
+// CHECK-LABEL: sil_coverage_map {{.*}}// coverage_label.foo
+func foo() { // CHECK-DAG: [[@LINE]]:12 -> [[@LINE+19]]:2 : 0
+  var x : Int32 = 0
+
+  label1: do { // CHECK-DAG: [[@LINE]]:14 -> [[@LINE+4]]:4 : 0
+    x += 1
+    break label1
+    x += 2     // CHECK-DAG: [[@LINE]]:5 -> [[@LINE+1]]:4 : zero
+  }
+
+  label2: do { // CHECK-DAG: [[@LINE]]:14 -> [[@LINE+7]]:4 : 0
+    x += 3         // CHECK-DAG: [[@LINE+1]]:11 -> [[@LINE+1]]:17 : 0
+    while (true) { // CHECK-DAG: [[@LINE]]:18 -> [[@LINE+3]]:6 : 1
+      x += 4
+      break label2 // Note: This exit affects the condition counter expr @ L15.
+    }              // CHECK-DAG: [[@LINE]]:6 -> [[@LINE+2]]:4 : (0 - 1)
+    x += 5
+  }
+
+  x += 6
+}
+
+foo()