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[PATCH, rs6000, 4.8/4.9] Fix alignment of non-Altivec vector struct fields


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/msg01072.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-protos.h (rs6000_special_adjust_field_align_p):
	Add prototype.
	* config/rs6000/rs6000.c (rs6000_special_adjust_field_align_p): New
	function.  Issue -Wpsabi warning if future GCC releases will use
	different field alignment rules for this type.
	* config/rs6000/sysv4.h (ADJUST_FIELD_ALIGN): Call it.
	* config/rs6000/linux64.h (ADJUST_FIELD_ALIGN): Likewise.
	* config/rs6000/freebsd64.h (ADJUST_FIELD_ALIGN): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/ppc64-abi-warn-3.c: New test.

	* gcc.c-torture/execute/20050316-1.x: Add -Wno-psabi.
	* gcc.c-torture/execute/20050604-1.x: Add -Wno-psabi.
	* gcc.c-torture/execute/20050316-3.x: New file.  Add -Wno-psabi.
	* gcc.c-torture/execute/pr23135.x: Likewise.

Index: gcc-4_9-branch/gcc/config/rs6000/rs6000-protos.h
===================================================================
--- gcc-4_9-branch.orig/gcc/config/rs6000/rs6000-protos.h
+++ gcc-4_9-branch/gcc/config/rs6000/rs6000-protos.h
@@ -155,6 +155,7 @@ extern void rs6000_split_logical (rtx []
 
 #ifdef TREE_CODE
 extern unsigned int rs6000_data_alignment (tree, unsigned int, enum data_align);
+extern bool rs6000_special_adjust_field_align_p (tree, unsigned int);
 extern unsigned int rs6000_special_round_type_align (tree, unsigned int,
 						     unsigned int);
 extern unsigned int darwin_rs6000_special_round_type_align (tree, unsigned int,
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
@@ -5871,6 +5871,34 @@ rs6000_data_alignment (tree type, unsign
   return align;
 }
 
+/* Previous GCC releases forced all vector types to have 16-byte alignment.  */
+
+bool
+rs6000_special_adjust_field_align_p (tree field, unsigned int computed)
+{
+  if (TARGET_ALTIVEC && TREE_CODE (TREE_TYPE (field)) == VECTOR_TYPE)
+    {
+      if (computed != 128)
+	{
+	  static bool warned;
+	  if (!warned && warn_psabi)
+	    {
+	      warned = true;
+	      inform (input_location,
+		      "the layout of aggregates containing vectors with"
+		      " %d-byte alignment will change in a future GCC release",
+		      computed / BITS_PER_UNIT);
+	    }
+	}
+      /* GCC 4.8/4.9 Note: To avoid any ABI change on a release branch, we
+	 keep the special treatment of vector types, but warn if there will
+	 be differences in future GCC releases.  */
+      return true;
+    }
+
+  return false;
+}
+
 /* AIX increases natural record alignment to doubleword if the first
    field is an FP double while the FP fields remain word aligned.  */
 
Index: gcc-4_9-branch/gcc/config/rs6000/sysv4.h
===================================================================
--- gcc-4_9-branch.orig/gcc/config/rs6000/sysv4.h
+++ gcc-4_9-branch/gcc/config/rs6000/sysv4.h
@@ -292,7 +292,7 @@ do {									\
 /* An expression for the alignment of a structure field FIELD if the
    alignment computed in the usual way is COMPUTED.  */
 #define ADJUST_FIELD_ALIGN(FIELD, COMPUTED)				      \
-	((TARGET_ALTIVEC && TREE_CODE (TREE_TYPE (FIELD)) == VECTOR_TYPE)     \
+	(rs6000_special_adjust_field_align_p ((FIELD), (COMPUTED))	      \
 	 ? 128 : COMPUTED)
 
 #undef  BIGGEST_FIELD_ALIGNMENT
Index: gcc-4_9-branch/gcc/config/rs6000/linux64.h
===================================================================
--- gcc-4_9-branch.orig/gcc/config/rs6000/linux64.h
+++ gcc-4_9-branch/gcc/config/rs6000/linux64.h
@@ -246,7 +246,7 @@ extern int dot_symbols;
 /* PowerPC64 Linux word-aligns FP doubles when -malign-power is given.  */
 #undef  ADJUST_FIELD_ALIGN
 #define ADJUST_FIELD_ALIGN(FIELD, COMPUTED) \
-  ((TARGET_ALTIVEC && TREE_CODE (TREE_TYPE (FIELD)) == VECTOR_TYPE)	\
+  (rs6000_special_adjust_field_align_p ((FIELD), (COMPUTED))		\
    ? 128								\
    : (TARGET_64BIT							\
       && TARGET_ALIGN_NATURAL == 0					\
Index: gcc-4_9-branch/gcc/config/rs6000/freebsd64.h
===================================================================
--- gcc-4_9-branch.orig/gcc/config/rs6000/freebsd64.h
+++ gcc-4_9-branch/gcc/config/rs6000/freebsd64.h
@@ -367,7 +367,7 @@ extern int dot_symbols;
 /* PowerPC64 Linux word-aligns FP doubles when -malign-power is given.  */
 #undef  ADJUST_FIELD_ALIGN
 #define ADJUST_FIELD_ALIGN(FIELD, COMPUTED) \
-  ((TARGET_ALTIVEC && TREE_CODE (TREE_TYPE (FIELD)) == VECTOR_TYPE)     \
+  (rs6000_special_adjust_field_align_p ((FIELD), (COMPUTED))		\
    ? 128                                                                \
    : (TARGET_64BIT                                                      \
       && TARGET_ALIGN_NATURAL == 0                                      \
Index: gcc-4_9-branch/gcc/testsuite/gcc.c-torture/execute/20050316-1.x
===================================================================
--- gcc-4_9-branch.orig/gcc/testsuite/gcc.c-torture/execute/20050316-1.x
+++ gcc-4_9-branch/gcc/testsuite/gcc.c-torture/execute/20050316-1.x
@@ -4,4 +4,5 @@ if { [check_effective_target_int16] } {
 	return 1
 }
 
+set additional_flags "-Wno-psabi"
 return 0;
Index: gcc-4_9-branch/gcc/testsuite/gcc.c-torture/execute/20050316-3.x
===================================================================
--- /dev/null
+++ gcc-4_9-branch/gcc/testsuite/gcc.c-torture/execute/20050316-3.x
@@ -0,0 +1,2 @@
+set additional_flags "-Wno-psabi"
+return 0
Index: gcc-4_9-branch/gcc/testsuite/gcc.c-torture/execute/20050604-1.x
===================================================================
--- gcc-4_9-branch.orig/gcc/testsuite/gcc.c-torture/execute/20050604-1.x
+++ gcc-4_9-branch/gcc/testsuite/gcc.c-torture/execute/20050604-1.x
@@ -6,4 +6,5 @@ if { [istarget "i?86-*-*"] || [istarget
 	set additional_flags "-mno-mmx"
 }
 
+set additional_flags "-Wno-psabi"
 return 0
Index: gcc-4_9-branch/gcc/testsuite/gcc.c-torture/execute/pr23135.x
===================================================================
--- /dev/null
+++ gcc-4_9-branch/gcc/testsuite/gcc.c-torture/execute/pr23135.x
@@ -0,0 +1,2 @@
+set additional_flags "-Wno-psabi"
+return 0
Index: gcc-4_9-branch/gcc/testsuite/gcc.target/powerpc/ppc64-abi-warn-3.c
===================================================================
--- /dev/null
+++ gcc-4_9-branch/gcc/testsuite/gcc.target/powerpc/ppc64-abi-warn-3.c
@@ -0,0 +1,9 @@
+/* { dg-do compile { target { powerpc*-*-linux* && lp64 } } } */
+/* { dg-require-effective-target powerpc_altivec_ok } */
+/* { dg-options "-maltivec" } */
+
+struct test
+  {
+    int a __attribute__((vector_size (8)));
+  }; /* { dg-message "note: the layout of aggregates containing vectors with 8-byte alignment will change" } */
+
-- 
  Dr. Ulrich Weigand
  GNU/Linux compilers and toolchain
  Ulrich.Weigand@de.ibm.com


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