Hello,
this is the variant intended for the 4.8/4.9 branches of the patch:
https://gcc.gnu.org/ml/gcc-patches/2014-07/msg00995.html
As discussed, it does *not* actually change ABI, but only warn when
encountering a situation where the ABI will change in a future GCC.
(Avoiding the specific term "GCC 4.10" here since I'm not certain
whether the next GCC release will in fact be called that ...)
Tested on powerpc64-linux and powerpc64le-linux; also verified using
the ABI compat suite (against an unpatched GCC) that this patch does
not change the ABI.
OK for 4.8/4.9 once the mainline patch is in?
Bye,
Ulrich
gcc/ChangeLog:
* config/rs6000/rs6000.c (rs6000_function_arg_boundary): Issue
-Wpsabi note when encountering a type where future GCC releases
will apply different alignment requirements.
gcc/testsuite/ChangeLog:
* gcc.target/powerpc/ppc64-abi-warn-2.c: New test.
Index: gcc-4_9-branch/gcc/config/rs6000/rs6000.c
===================================================================
--- gcc-4_9-branch.orig/gcc/config/rs6000/rs6000.c
+++ gcc-4_9-branch/gcc/config/rs6000/rs6000.c
@@ -9180,14 +9180,51 @@ rs6000_function_arg_boundary (enum machi
|| (type && TREE_CODE (type) == VECTOR_TYPE
&& int_size_in_bytes (type) >= 16))
return 128;
- else if (((TARGET_MACHO && rs6000_darwin64_abi)
- || DEFAULT_ABI == ABI_ELFv2
- || (DEFAULT_ABI == ABI_AIX && !rs6000_compat_align_parm))
- && mode == BLKmode
- && type && TYPE_ALIGN (type) > 64)
+
+ /* Aggregate types that need > 8 byte alignment are quadword-aligned
+ in the parameter area in the ELFv2 ABI, and in the AIX ABI unless
+ -mcompat-align-parm is used. */
+ if (((DEFAULT_ABI == ABI_AIX && !rs6000_compat_align_parm)
+ || DEFAULT_ABI == ABI_ELFv2)
+ && type && TYPE_ALIGN (type) > 64)
+ {
+ /* "Aggregate" means any AGGREGATE_TYPE except for single-element
+ or homogeneous float/vector aggregates here. We already handled
+ vector aggregates above, but still need to check for float here. */
+ bool aggregate_p = (AGGREGATE_TYPE_P (type)
+ && !SCALAR_FLOAT_MODE_P (elt_mode));
+
+ /* We used to check for BLKmode instead of the above aggregate type
+ check. Warn when this results in any difference to the ABI. */
+ if (aggregate_p != (mode == BLKmode))
+ {
+ static bool warned;
+ if (!warned && warn_psabi)
+ {
+ warned = true;
+ inform (input_location,
+ "the ABI of passing aggregates with %d-byte alignment"
+ " will change in a future GCC release",
+ (int) TYPE_ALIGN (type) / BITS_PER_UNIT);
+ }
+ }
+
+ /* GCC 4.8/4.9 Note: To avoid any ABI change on a release branch, we
+ keep using the BLKmode check, but warn if there will be differences
+ in future GCC releases. */
+ if (mode == BLKmode)
+ return 128;
+ }
+
+ /* Similar for the Darwin64 ABI. Note that for historical reasons we
+ implement the "aggregate type" check as a BLKmode check here; this
+ means certain aggregate types are in fact not aligned. */
+ if (TARGET_MACHO && rs6000_darwin64_abi
+ && mode == BLKmode
+ && type && TYPE_ALIGN (type) > 64)
return 128;
- else
- return PARM_BOUNDARY;
+
+ return PARM_BOUNDARY;
}
/* The offset in words to the start of the parameter save area. */
Index: gcc-4_9-branch/gcc/testsuite/gcc.target/powerpc/ppc64-abi-warn-2.c
===================================================================
--- /dev/null
+++ gcc-4_9-branch/gcc/testsuite/gcc.target/powerpc/ppc64-abi-warn-2.c
@@ -0,0 +1,11 @@
+/* { dg-do compile { target { powerpc*-*-linux* && lp64 } } } */
+
+struct test
+ {
+ long a __attribute__((aligned (16)));
+ };
+
+void test (struct test a) /* { dg-message "note: the ABI of passing aggregates
with 16-byte alignment will change" } */
+{
+}
+
--
Dr. Ulrich Weigand
GNU/Linux compilers and toolchain
ulrich.weig...@de.ibm.com
