r332801 - CodeGen: block capture shouldn't ICE

[JF Bastien via cfe-commits]

Author: jfb
Date: Fri May 18 21:21:26 2018
New Revision: 332801

URL: http://llvm.org/viewvc/llvm-project?rev=332801&view=rev
Log:
CodeGen: block capture shouldn't ICE

When a lambda capture captures a __block in the same statement, the compiler asserts out because isCapturedBy assumes that an Expr can only be a BlockExpr, StmtExpr, or if it's a Stmt then all the statement's children are expressions. That's wrong, we need to visit all sub-statements even if they're not expressions to see if they also capture.

Fix this issue by pulling out the isCapturedBy logic to use RecursiveASTVisitor.

<rdar://problem/39926584>

Added:
    cfe/trunk/test/CodeGenCXX/block-capture.cpp
Modified:
    cfe/trunk/lib/CodeGen/CGDecl.cpp

Modified: cfe/trunk/lib/CodeGen/CGDecl.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGDecl.cpp?rev=332801&r1=332800&r2=332801&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGDecl.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGDecl.cpp Fri May 18 21:21:26 2018
@@ -1244,17 +1244,30 @@ CodeGenFunction::EmitAutoVarAlloca(const
   return emission;
 }
 
+static bool isCapturedBy(const VarDecl &, const Expr *);
+
+/// Determines whether the given __block variable is potentially
+/// captured by the given statement.
+static bool isCapturedBy(const VarDecl &Var, const Stmt *S) {
+  if (const Expr *E = dyn_cast<Expr>(S))
+    return isCapturedBy(Var, E);
+  for (const Stmt *SubStmt : S->children())
+    if (isCapturedBy(Var, SubStmt))
+      return true;
+  return false;
+}
+
 /// Determines whether the given __block variable is potentially
 /// captured by the given expression.
-static bool isCapturedBy(const VarDecl &var, const Expr *e) {
+static bool isCapturedBy(const VarDecl &Var, const Expr *E) {
   // Skip the most common kinds of expressions that make
   // hierarchy-walking expensive.
-  e = e->IgnoreParenCasts();
+  E = E->IgnoreParenCasts();
 
-  if (const BlockExpr *be = dyn_cast<BlockExpr>(e)) {
-    const BlockDecl *block = be->getBlockDecl();
-    for (const auto &I : block->captures()) {
-      if (I.getVariable() == &var)
+  if (const BlockExpr *BE = dyn_cast<BlockExpr>(E)) {
+    const BlockDecl *Block = BE->getBlockDecl();
+    for (const auto &I : Block->captures()) {
+      if (I.getVariable() == &Var)
         return true;
     }
 
@@ -1262,19 +1275,19 @@ static bool isCapturedBy(const VarDecl &
     return false;
   }
 
-  if (const StmtExpr *SE = dyn_cast<StmtExpr>(e)) {
+  if (const StmtExpr *SE = dyn_cast<StmtExpr>(E)) {
     const CompoundStmt *CS = SE->getSubStmt();
     for (const auto *BI : CS->body())
-      if (const auto *E = dyn_cast<Expr>(BI)) {
-        if (isCapturedBy(var, E))
-            return true;
+      if (const auto *BIE = dyn_cast<Expr>(BI)) {
+        if (isCapturedBy(Var, BIE))
+          return true;
       }
       else if (const auto *DS = dyn_cast<DeclStmt>(BI)) {
           // special case declarations
           for (const auto *I : DS->decls()) {
               if (const auto *VD = dyn_cast<VarDecl>((I))) {
                 const Expr *Init = VD->getInit();
-                if (Init && isCapturedBy(var, Init))
+                if (Init && isCapturedBy(Var, Init))
                   return true;
               }
           }
@@ -1286,8 +1299,8 @@ static bool isCapturedBy(const VarDecl &
     return false;
   }
 
-  for (const Stmt *SubStmt : e->children())
-    if (isCapturedBy(var, cast<Expr>(SubStmt)))
+  for (const Stmt *SubStmt : E->children())
+    if (isCapturedBy(Var, SubStmt))
       return true;
 
   return false;

Added: cfe/trunk/test/CodeGenCXX/block-capture.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/block-capture.cpp?rev=332801&view=auto
==============================================================================
--- cfe/trunk/test/CodeGenCXX/block-capture.cpp (added)
+++ cfe/trunk/test/CodeGenCXX/block-capture.cpp Fri May 18 21:21:26 2018
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -x c++ -std=c++11 -fblocks -emit-llvm %s -o - | FileCheck %s
+
+// CHECK: %struct.__block_byref_baz = type { i8*, %struct.__block_byref_baz*, i32, i32, i32 }
+// CHECK: [[baz:%[0-9a-z_]*]] = alloca %struct.__block_byref_baz
+// CHECK: [[bazref:%[0-9a-z_\.]*]] = getelementptr inbounds %struct.__block_byref_baz, %struct.__block_byref_baz* [[baz]], i32 0, i32 1
+// CHECK: store %struct.__block_byref_baz* [[baz]], %struct.__block_byref_baz** [[bazref]]
+// CHECK: [[disposable:%[0-9a-z_]*]] = bitcast %struct.__block_byref_baz* [[baz]] to i8*
+// CHECK: call void @_Block_object_dispose(i8* [[disposable]]
+
+int main() {
+  __block int baz = [&]() { return 0; }();
+  return 0;
+}