AArch64: implement AAPCS layout rules for bit-fields.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@226294 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Basic/Targets.cpp

@@ -4650,6 +4650,13 @@ public:
     // specifiers.
     NoAsmVariants = true;
 
+    // AAPCS gives rules for bitfields. 7.1.7 says: "The container type
+    // contributes to the alignment of the containing aggregate in the same way
+    // a plain (non bit-field) member of that type would, without exception for
+    // zero-sized or anonymous bit-fields."
+    UseBitFieldTypeAlignment = true;
+    UseZeroLengthBitfieldAlignment = true;
+
     // AArch64 targets default to using the ARM C++ ABI.
     TheCXXABI.set(TargetCXXABI::GenericAArch64);
   }

test/CodeGenCXX/aarch64-aapcs-zerolength-bitfield.cpp

@@ -0,0 +1,249 @@
+// REQUIRES: aarch64-registered-target
+// RUN: %clang_cc1 -triple aarch64-linux-gnu -x c++ -std=c++1z %s -verify
+// expected-no-diagnostics
+
+#include <stddef.h>
+
+struct t1
+{
+  int foo : 1;
+  char : 0;
+  char bar;
+
+};
+static_assert(offsetof(struct t1, bar) == 1);
+static_assert(sizeof(struct t1) == 4);
+
+struct t2
+{
+  int foo : 1;
+  short : 0;
+  char bar;
+};
+static_assert(offsetof(struct t2, bar) == 2);
+static_assert(sizeof(struct t2) == 4);
+
+struct t3
+{
+  int foo : 1;
+  int : 0;
+  char bar;
+};
+static_assert(offsetof(struct t3, bar) == 4);
+static_assert(sizeof(struct t3) == 8);
+
+struct t4
+{
+  int foo : 1;
+  long : 0;
+  char bar;
+};
+static_assert(offsetof(struct t4, bar) == 8);
+static_assert(sizeof(struct t4) == 16);
+
+struct t5
+{
+  int foo : 1;
+  long long : 0;
+  char bar;
+};
+static_assert(offsetof(struct t5, bar) == 8);
+static_assert(sizeof(struct t5) == 16);
+
+struct t6
+{
+  int foo : 1;
+  char : 0;
+  char bar : 1;
+  char bar2;
+};
+static_assert(offsetof(struct t6, bar2) == 2);
+static_assert(sizeof(struct t6) == 4);
+
+struct t7
+{
+  int foo : 1;
+  short : 0;
+  char bar1 : 1;
+  char bar2;
+};
+static_assert(offsetof(struct t7, bar2) == 3);
+static_assert(sizeof(struct t7) == 4);
+
+struct t8
+{
+  int foo : 1;
+  int : 0;
+  char bar1 : 1;
+  char bar2;
+};
+static_assert(offsetof(struct t8, bar2) == 5);
+static_assert(sizeof(struct t8) == 8);
+
+struct t9
+{
+  int foo : 1;
+  long : 0;
+  char bar1 : 1;
+  char bar2;
+};
+static_assert(offsetof(struct t9, bar2) == 9);
+static_assert(sizeof(struct t9) == 16);
+
+struct t10
+{
+  int foo : 1;
+  long long : 0;
+  char bar1 : 1;
+  char bar2;
+};
+static_assert(offsetof(struct t10, bar2) == 9);
+static_assert(sizeof(struct t10) == 16);
+
+struct t11
+{
+  int foo : 1;
+  long long : 0;
+  char : 0;
+  char bar1 : 1;
+  char bar2;
+};
+static_assert(offsetof(struct t11, bar2) == 9);
+static_assert(sizeof(struct t11) == 16);
+
+struct t12
+{
+  int foo : 1;
+  char : 0;
+  long long : 0;
+  char : 0;
+  char bar;
+};
+static_assert(offsetof(struct t12, bar) == 8);
+static_assert(sizeof(struct t12) == 16);
+
+struct t13
+{
+  char foo;
+  long : 0;
+  char bar;
+};
+static_assert(offsetof(struct t13, bar) == 8);
+static_assert(sizeof(struct t13) == 16);
+
+struct t14
+{
+  char foo1;
+  int : 0;
+  char foo2 : 1;
+  short foo3 : 16;
+  char : 0;
+  short foo4 : 16;
+  char bar1;
+  int : 0;
+  char bar2;
+};
+static_assert(offsetof(struct t14, bar1) == 10);
+static_assert(offsetof(struct t14, bar2) == 12);
+static_assert(sizeof(struct t14) == 16);
+
+struct t15
+{
+  char foo;
+  char : 0;
+  int : 0;
+  char bar;
+  long : 0;
+  char : 0;
+};
+static_assert(offsetof(struct t15, bar) == 4);
+static_assert(sizeof(struct t15) == 8);
+
+struct t16
+{
+  long : 0;
+  char bar;
+};
+static_assert(offsetof(struct t16, bar) == 0);
+static_assert(sizeof(struct t16) == 8);
+
+struct t17
+{
+  char foo;
+  long : 0;
+  long : 0;
+  char : 0;
+  char bar;
+};
+static_assert(offsetof(struct t17, bar) == 8);
+static_assert(sizeof(struct t17) == 16);
+
+struct t18
+{
+  long : 0;
+  long : 0;
+  char : 0;
+};
+static_assert(sizeof(struct t18) == 8);
+
+struct t19
+{
+  char foo1;
+  long foo2 : 1;
+  char : 0;
+  long foo3 : 32;
+  char bar;
+};
+static_assert(offsetof(struct t19, bar) == 6);
+static_assert(sizeof(struct t19) == 8);
+
+struct t20
+{
+  short : 0;
+  int foo : 1;
+  long : 0;
+  char bar;
+};
+static_assert(offsetof(struct t20, bar) == 8);
+static_assert(sizeof(struct t20) == 16);
+
+struct t21
+{
+  short : 0;
+  int foo1 : 1;
+  char : 0;
+  int foo2 : 16;
+  long : 0;
+  char bar1;
+  int bar2;
+  long bar3;
+  char foo3 : 8;
+  char : 0;
+  long : 0;
+  int foo4 : 32;
+  short foo5: 1;
+  long bar4;
+  short foo6: 16;
+  short foo7: 16;
+  short foo8: 16;
+};
+static_assert(offsetof(struct t21, bar1) == 8);
+static_assert(offsetof(struct t21, bar2) == 12);
+static_assert(offsetof(struct t21, bar3) == 16);
+static_assert(offsetof(struct t21, bar4) == 40);
+static_assert(sizeof(struct t21) == 56);
+
+// The rules also apply to anonymous bitfields with non-zero length.
+struct t22
+{
+  char foo;
+  short :2;
+  char bar;
+};
+static_assert(alignof(struct t22) == 2);
+static_assert(offsetof(struct t22, bar) == 2);
+
+int main() {
+  return 0;
+}
+