[clang] b5aef90 - [Clang] Fix instantiation of OpaqueValueExprs (Bug #45964)

[Raul Tambre via cfe-commits]

Author: Jason Rice
Date: 2021-11-06T10:06:38+02:00
New Revision: b5aef90d4656c5188759d03e2c5c3dc3d8bb398b

URL: https://github.com/llvm/llvm-project/commit/b5aef90d4656c5188759d03e2c5c3dc3d8bb398b
DIFF: https://github.com/llvm/llvm-project/commit/b5aef90d4656c5188759d03e2c5c3dc3d8bb398b.diff

LOG: [Clang] Fix instantiation of OpaqueValueExprs (Bug #45964)

The structured bindings decomposition of a non-dependent array in a dependent context (a template) were, upon instantiation, creating nested OpaqueValueExprs that would trigger assertions in CodeGen. Additionally the OpaqueValuesExpr's contained SourceExpr is being emitted in CodeGen, but there was no code for its transform in template instantiation. This would trigger other assertions such as when emitting a DeclRefExpr that refers to a VarDecl that is not marked as ODR-used.

This is all based on cursory deduction, but with the way the code flows from SemaTemplateInstantiate back to SemaInit, it is apparent that the nesting of OpaqueValueExpr is unintentional.

This commit fixes https://bugs.llvm.org/show_bug.cgi?id=45964 and possible other issues involving OpaqueValueExprs in template instantiations might be resolved.

Reviewed By: aaron.ballman, rjmccall

Differential Revision: https://reviews.llvm.org/D108482

Added: 
    clang/test/CodeGenCXX/pr45964-decomp-transform.cpp

Modified: 
    clang/lib/Sema/TreeTransform.h

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index ad61a6782976e..3f0f21b2e6e73 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -3853,8 +3853,10 @@ ExprResult TreeTransform<Derived>::TransformInitializer(Expr *Init,
   if (auto *FE = dyn_cast<FullExpr>(Init))
     Init = FE->getSubExpr();
 
-  if (auto *AIL = dyn_cast<ArrayInitLoopExpr>(Init))
-    Init = AIL->getCommonExpr();
+  if (auto *AIL = dyn_cast<ArrayInitLoopExpr>(Init)) {
+    OpaqueValueExpr *OVE = AIL->getCommonExpr();
+    Init = OVE->getSourceExpr();
+  }
 
   if (MaterializeTemporaryExpr *MTE = dyn_cast<MaterializeTemporaryExpr>(Init))
     Init = MTE->getSubExpr();

diff  --git a/clang/test/CodeGenCXX/pr45964-decomp-transform.cpp b/clang/test/CodeGenCXX/pr45964-decomp-transform.cpp
new file mode 100644
index 0000000000000..927624ca6e370
--- /dev/null
+++ b/clang/test/CodeGenCXX/pr45964-decomp-transform.cpp
@@ -0,0 +1,27 @@
+// RUN: %clang_cc1 -std=c++17 -triple x86_64-linux-gnu -emit-llvm -o - %s | FileCheck %s
+
+int a[1];
+// CHECK: @a = global [1 x i32] zeroinitializer
+template <int>
+void test_transform() {
+  auto [b] = a;
+}
+void (*d)(){test_transform<0>};
+// CHECK-LABEL: define {{.*}} @_Z14test_transformILi0EEvv
+// CHECK:       [[ENTRY:.*]]:
+// CHECK-NEXT:  [[ARR:%.*]] = alloca [1 x i32]
+// CHECK-NEXT:  [[BEGIN:%.*]] = getelementptr inbounds [1 x i32], [1 x i32]* [[ARR]], i64 0, i64 0
+// CHECK-NEXT:  br label %[[BODY:.*]]
+// CHECK-EMPTY:
+// CHECK-NEXT:  [[BODY]]:
+// CHECK-NEXT:  [[CUR:%.*]] = phi i64 [ 0, %[[ENTRY]] ], [ [[NEXT:%.*]], %[[BODY]] ]
+// CHECK-NEXT:  [[DEST:%.*]] = getelementptr inbounds i32, i32* [[BEGIN]], i64 [[CUR]]
+// CHECK-NEXT:  [[SRC:%.*]] = getelementptr inbounds [1 x i32], [1 x i32]* @a, i64 0, i64 [[CUR]]
+// CHECK-NEXT:  [[X:%.*]] = load i32, i32* [[SRC]]
+// CHECK-NEXT:  store i32 [[X]], i32* [[DEST]]
+// CHECK-NEXT:  [[NEXT]] = add nuw i64 [[CUR]], 1
+// CHECK-NEXT:  [[EQ:%.*]] = icmp eq i64 [[NEXT]], 1
+// CHECK-NEXT:  br i1 [[EQ]], label %[[FIN:.*]], label %[[BODY]]
+// CHECK-EMPTY:
+// CHECK-NEXT:  [[FIN]]:
+// CHECK-NEXT:  ret void