PR40642: Fix determination of whether the final statement of a statement

expression is a discarded-value expression.

Summary:
We used to get this wrong in three ways:

1) During parsing, an expression-statement followed by the }) ending a
   statement expression was always treated as producing the value of the
   statement expression. That's wrong for ({ if (1) expr; })
2) During template instantiation, various kinds of statement (most
   statements not appearing directly in a compound-statement) were not
   treated as discarded-value expressions, resulting in missing volatile
   loads (etc).
3) In all contexts, an expression-statement with attributes was not
   treated as producing the value of the statement expression, eg
   ({ [[attr]] expr; }).

Also fix incorrect enforcement of OpenMP rule that directives can "only
be placed in the program at a position where ignoring or deleting the
directive would result in a program with correct syntax". In particular,
a label (be it goto, case, or default) should not affect whether
directives are permitted.

Reviewers: aaron.ballman, rjmccall

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D57984

llvm-svn: 354090

1 files changed, 10 insertions, 4 deletions

diff --git a/clang/test/OpenMP/taskyield_messages.cpp b/clang/test/OpenMP/taskyield_messages.cpp
index fd98a8786f1..48f741df915 100644
--- a/clang/test/OpenMP/taskyield_messages.cpp
+++ b/clang/test/OpenMP/taskyield_messages.cpp
@@ -29,7 +29,7 @@ T tmain(T argc) {
 #pragma omp taskyield // expected-error {{'#pragma omp taskyield' cannot be an immediate substatement}}
     switch (argc)
     case 1:
-#pragma omp taskyield
+#pragma omp taskyield // expected-error {{'#pragma omp taskyield' cannot be an immediate substatement}}
   switch (argc)
   case 1: {
 #pragma omp taskyield
@@ -49,10 +49,13 @@ T tmain(T argc) {
 #pragma omp taskyield
     }
 label:
-#pragma omp taskyield // expected-error {{'#pragma omp taskyield' cannot be an immediate substatement}}
+#pragma omp taskyield
 label1 : {
 #pragma omp taskyield
 }
+if (1)
+  label2:
+#pragma omp taskyield // expected-error {{'#pragma omp taskyield' cannot be an immediate substatement}}
 
   return T();
 }
@@ -83,7 +86,7 @@ int main(int argc, char **argv) {
 #pragma omp taskyield // expected-error {{'#pragma omp taskyield' cannot be an immediate substatement}}
     switch (argc)
     case 1:
-#pragma omp taskyield
+#pragma omp taskyield // expected-error {{'#pragma omp taskyield' cannot be an immediate substatement}}
   switch (argc)
   case 1: {
 #pragma omp taskyield
@@ -103,10 +106,13 @@ int main(int argc, char **argv) {
 #pragma omp taskyield
     }
 label:
-#pragma omp taskyield // expected-error {{'#pragma omp taskyield' cannot be an immediate substatement}}
+#pragma omp taskyield
 label1 : {
 #pragma omp taskyield
 }
+if (1)
+  label2:
+#pragma omp taskyield // expected-error {{'#pragma omp taskyield' cannot be an immediate substatement}}
 
   return tmain(argc);
 }