re PR c/87691 (transparent_union attribute does not work with MODE_PARTIAL_INT)

2018-11-07  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

	PR c/87691
	
	gcc/ChangeLog:
	* stor-layout.c (compute_record_mode): Set TYPE_MODE of UNION_TYPE
	to the mode of the widest field iff the widest field has mode class
	MODE_INT, or MODE_PARTIAL_INT and the union would be passed by
	reference.

	gcc/testsuite/ChangeLog:
	* gcc.target/msp430/pr87691.c: New test.

From-SVN: r265894

2 files changed, 48 insertions, 2 deletions

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 689d7a7f11b..51f1b6085f8 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,6 +1,11 @@
-2018-11-17  Nikolai Merinov <n.merinov@inango-systems.com>
+2018-11-07  Jozef Lawrynowicz  <jozef.l@mittosystems.com>
 
-         * gcc.dg/Wno-attribute-warning.c: New test.
+	PR c/87691
+	* gcc.target/msp430/pr87691.c: New test.
+
+2018-11-07  Nikolai Merinov  <n.merinov@inango-systems.com>
+
+	* gcc.dg/Wno-attribute-warning.c: New test.
 
 2018-11-07  Nathan Sidwell  <nathan@acm.org>
 
diff --git a/gcc/testsuite/gcc.target/msp430/pr87691.c b/gcc/testsuite/gcc.target/msp430/pr87691.c
new file mode 100644
index 00000000000..c00425d2452
--- /dev/null
+++ b/gcc/testsuite/gcc.target/msp430/pr87691.c
@@ -0,0 +1,41 @@
+/* PR 87691 - Test that a union containing __int20 and a float is not treated as
+   20-bits in size.  */
+
+/* { dg-do compile } */
+/* { dg-skip-if "no __int20 for mcpu=msp430" { *-*-* } { "-mcpu=msp430" } { "" } } */
+/* { dg-final { scan-assembler-not "MOVX.A" } } */
+
+/* To move a 20-bit value from memory (using indexed or indirect register
+   mode), onto the stack (also addressed using indexed or indirect register
+   mode), MOVX.A must be used. MOVA does not support these addressing modes.
+   Therefore, to check that the union is not manipulated as a 20-bit type,
+   test that no MOVX.A instructions are present in the assembly.
+
+   MOVA is used to fill/spill u.i, but if the union is treated as 20 bits in
+   size, MOVX.A would be used. No other __int20 operations are present
+   in the source, so there will be no valid uses of MOVX.A in the resulting
+   assembly.  */
+
+union U1
+{
+  float f;
+  __int20 i;
+};
+
+union U2
+{
+  __int20 i;
+  float f;
+};
+
+float foo1 (union U1 u)
+{
+  u.i += 42;
+  return u.f;
+}
+
+float foo2 (union U2 u)
+{
+  u.i += 42;
+  return u.f;
+}