[PATCH] AIX alignment of double _Complex (PR 99492)

[David Edelsohn via Gcc-patches]

    AIX word-aligns floating point doubles.  This behavior also extends to
    double _Complex, which had been overlooked when compiler support for
    double _Complex was added.

    This patch adds DCmode to the modes whose alignment is adjusted and
    adds a testcase to confirm the correct alignment.

Bootstrapped on powerpc-ibm-aix7.2.3.0.

    gcc/ChangeLog:

    2021-03-10  David Edelsohn  <dje....@gmail.com>

            PR target/99492
            * config/rs6000/aix.h (ADJUST_FIELD_ALIGN): Add check for DCmode.
            * config/rs6000/rs6000.c (rs6000_special_round_type_align): Same.

    gcc/testsuite/ChangeLog:

    2021-03-10  David Edelsohn  <dje....@gmail.com>

            PR target/99492
            * gcc.target/powerpc/pr99492.c: New testcase.

diff --git a/gcc/config/rs6000/aix.h b/gcc/config/rs6000/aix.h
index 5e8743ab782..2db50c8007f 100644
--- a/gcc/config/rs6000/aix.h
+++ b/gcc/config/rs6000/aix.h
@@ -224,7 +224,8 @@
 /* AIX word-aligns FP doubles but doubleword-aligns 64-bit ints.  */
 #define ADJUST_FIELD_ALIGN(FIELD, TYPE, COMPUTED) \
   ((TARGET_ALIGN_NATURAL == 0                                          \
-    && TYPE_MODE (strip_array_types (TYPE)) == DFmode)                 \
+    && (TYPE_MODE (strip_array_types (TYPE)) == DFmode                 \
+       || TYPE_MODE (strip_array_types (TYPE)) == DCmode))             \
    ? MIN ((COMPUTED), 32)                                              \
    : (COMPUTED))

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index c89fb6e124a..35ecf5ac9ab 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -7855,7 +7855,8 @@ rs6000_special_round_type_align (tree type,
unsigned int computed,
       while (TREE_CODE (type) == ARRAY_TYPE)
        type = TREE_TYPE (type);

-      if (type != error_mark_node && TYPE_MODE (type) == DFmode)
+      if (type != error_mark_node
+         && (TYPE_MODE (type) == DFmode || TYPE_MODE (type) == DCmode))
        align = MAX (align, 64);
     }
 diff --git a/gcc/testsuite/gcc.target/powerpc/pr99492.c
b/gcc/testsuite/gcc.target/powerpc/pr99492.c
new file mode 100644
index 00000000000..ae36cb3baf7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr99492.c
@@ -0,0 +1,50 @@
+/* { dg-do run { target { powerpc*-ibm-aix* } } } */
+/* { dg-options "" } */
+
+void abort (void);
+
+struct A {
+    double _Complex a[64];
+};
+
+struct B {
+    double b[64];
+};
+
+struct C {
+    char c1;
+    double _Complex c2;
+};
+
+struct D {
+    char c1;
+    double c2;
+};
+
+int main() {
+  if (__alignof(double _Complex) != 8)
+    abort();
+
+  if (__alignof(struct A) != 8)
+    abort;
+
+  if (__alignof(struct C) != 4)
+    abort;
+
+  if (__builtin_offsetof(struct C, c2) != 4)
+    abort();
+
+
+  if (__alignof(double) != 8)
+    abort();
+
+  if (__alignof(struct B) != 8)
+    abort();
+
+  if (__alignof(struct D) != 4)
+    abort();
+
+  if (__builtin_offsetof(struct D, c2) != 4)
+    abort();
+
+  return 0;
+}