Fix for PR14269: Clang crashes when a bit field is used as inline ass…

…embler

input / output with memory constraint.
One generally can't get address of a bit field, so the general solution is to
error on such cases. GCC does the same.

Patch by Andrey Bokhanko

Differential Revision: http://reviews.llvm.org/D10086

llvm-svn: 239153

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -6338,6 +6338,9 @@ let CategoryName = "Inline Assembly Issue" in {
     "remove the cast or build with -fheinous-gnu-extensions">;
   def err_invalid_asm_value_for_constraint
       : Error <"value '%0' out of range for constraint '%1'">;
+  def err_asm_bitfield_in_memory_constraint
+      : Error <"reference to a bit-field in asm "
+      "%select{input|output}0 with a memory constraint '%1'">;
 
   def warn_asm_label_on_auto_decl : Warning<
     "ignored asm label '%0' on automatic variable">;

clang/lib/Sema/SemaStmtAsm.cpp

@@ -154,6 +154,14 @@ StmtResult Sema::ActOnGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
     if (CheckNakedParmReference(OutputExpr, *this))
       return StmtError();
 
+    // Bitfield can't be referenced with a pointer.
+    if (Info.allowsMemory() && OutputExpr->refersToBitField())
+      return StmtError(Diag(OutputExpr->getLocStart(),
+                            diag::err_asm_bitfield_in_memory_constraint)
+                       << 1
+                       << Info.getConstraintStr()
+                       << OutputExpr->getSourceRange());
+
     OutputConstraintInfos.push_back(Info);
 
     // If this is dependent, just continue.
@@ -230,6 +238,14 @@ StmtResult Sema::ActOnGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
     if (CheckNakedParmReference(InputExpr, *this))
       return StmtError();
 
+    // Bitfield can't be referenced with a pointer.
+    if (Info.allowsMemory() && InputExpr->refersToBitField())
+      return StmtError(Diag(InputExpr->getLocStart(),
+                            diag::err_asm_bitfield_in_memory_constraint)
+                       << 0
+                       << Info.getConstraintStr()
+                       << InputExpr->getSourceRange());
+
     // Only allow void types for memory constraints.
     if (Info.allowsMemory() && !Info.allowsRegister()) {
       if (CheckAsmLValue(InputExpr, *this))

clang/test/Sema/asm.c

@@ -204,3 +204,20 @@ void fn6() {
             : "=rm"(a), "=rm"(a)
             : "11m"(a)) // expected-error {{invalid input constraint '11m' in asm}}
 }
+
+// PR14269
+typedef struct test16_foo {
+  unsigned int field1 : 1;
+  unsigned int field2 : 2;
+  unsigned int field3 : 3;
+} test16_foo;
+test16_foo x;
+void test16()
+{
+  __asm__("movl $5, %0"
+          : "=rm" (x.field2)); // expected-error {{reference to a bit-field in asm output with a memory constraint '=rm'}}
+  __asm__("movl $5, %0"
+          :
+          : "m" (x.field3)); // expected-error {{reference to a bit-field in asm input with a memory constraint 'm'}}
+}
+