This patch has bootstrapped and tested on powerpc64le-unknown-linux-gnu and
powerpc64be-unknown-linux-gnu (both 32-bit and 64-bit) and
powerpc64-unknown-freebsd11.0 (big endian) with no regressions. Is it ok to
fix this on the trunk?
The problem described in PR66337
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D66337) is that compiling for
PowerPC targets with the -malign-power command-line option results in invalid
field offsets for certain structure members. As identified in the problem
report, this results from a macro definition present in both
config/rs6000/{freebsd64,linux64}.h, which in both cases is introduced by the
comment:
/* PowerPC64 Linux word-aligns FP doubles when -malign-power is given. */
I have consulted various ABI documents, including "64-bit PowerPC ELF
Application Binary Interface Supplement 1.9"
(http://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi.html), "Power
Architecture 64-Bit ELF V2 ABI Specification"
(https://members.openpowerfoundation.org/document/dl/576), and "Power
Architecture(R) 32-bit Application Binary Interface Supplement 1.0 - Linux(R) &
Embedded"
(https://www.power.org/documentation/power-architecture-32-bit-abi-supplement-1-0-embeddedlinuxunified/).
I have not been able to find any basis for this comment and thus am
concluding that the comment and existing implementation are incorrect.
The implemented patch removes the comment and changes the macro definition so
that field alignment calculations on 64-bit architectures ignore the
-malign-power command-line option. With this fix, the test case identified in
the PR behaves as was expected by the submitter.
gcc/ChangeLog:
2016-02-17 Kelvin Nilsen <kel...@gcc.gnu.org>
PR target/66337
* config/rs6000/freebsd64.h: Remove erroneous comment and correct
definition of ADJUST_FIELD_ALIGN macro.
* config/rs6000/linux64.h: Remove erroneous comment and correct
definition of ADJUST_FIELD_ALIGN macro.
gcc/testsuite/ChangeLog:
2016-02-17 Kelvin Nilsen <kel...@gcc.gnu.org>
PR target/66337
* g++.dg/pr66337-1.C: New test.
Index: gcc/testsuite/g++.dg/pr66337-1.C
===================================================================
--- gcc/testsuite/g++.dg/pr66337-1.C (revision 0)
+++ gcc/testsuite/g++.dg/pr66337-1.C (revision 233507)
@@ -0,0 +1,77 @@
+/* { dg-do run { target { powerpc*-*-* } } } */
+/* { dg-options "-std=c++11 -malign-power -O2" } */
+
+/* Power ABI for 32-bit and 64-bit compilers place the same alignment
+ restrictions on long longs and doubles. */
+
+typedef double _Tp;
+
+struct _Tp2 {
+ char b;
+ int i;
+ char c;
+ long long l;
+ _Tp _M_t;
+};
+
+extern _Tp2 tp2e;
+
+struct _ST1 {
+ char a;
+};
+
+struct _ST2 {
+ int b;
+};
+
+struct _ST3 {
+ float f;
+};
+
+struct _ST4 {
+ double d;
+};
+
+struct _ST5 {
+ char a;
+ double d;
+};
+
+struct _ST6 {
+ double d;
+ char a;
+};
+
+int main ()
+{
+ int a = alignof (_Tp2);
+ int b = __alignof__(_Tp2::_M_t);
+ int c = alignof(_Tp);
+ int d = __alignof__(tp2e._M_t);
+ int e = alignof(_Tp2::_M_t);
+
+ int f = __alignof__(_Tp2::l);
+ int g = alignof (long long);
+ int h = __alignof__(tp2e.l);
+ int i = alignof(_Tp2::l);
+
+ if ((a != 8) || (b != 8) || (c != 8) || (d != 8) || (e != 8)
+ || (f != 8) || (g != 8) || (h != 8) || (i != 8))
+ return -1;
+
+ a = sizeof (_ST1);
+ b = sizeof (_ST2);
+ c = sizeof (_ST3);
+ d = sizeof (_ST4);
+ e = sizeof (_ST5);
+ f = sizeof (_ST6);
+ g = sizeof (_Tp2);
+
+ if ((a != 1) || (b != 4) || (c != 4) || (d != 8)
+ || (e != 16) || (f != 16) || (g != 32))
+ return -2;
+
+ /* success */
+ return 0;
+}
+
Index: gcc/config/rs6000/freebsd64.h
===================================================================
--- gcc/config/rs6000/freebsd64.h (revision 233308)
+++ gcc/config/rs6000/freebsd64.h (working copy)
@@ -363,16 +363,10 @@ extern int dot_symbols;
/* Use standard DWARF numbering for DWARF debugging information. */
#define RS6000_USE_DWARF_NUMBERING
-/* PowerPC64 Linux word-aligns FP doubles when -malign-power is given. */
#undef ADJUST_FIELD_ALIGN
#define ADJUST_FIELD_ALIGN(FIELD, COMPUTED) \
(rs6000_special_adjust_field_align_p ((FIELD), (COMPUTED)) \
- ? 128 \
- : (TARGET_64BIT \
- && TARGET_ALIGN_NATURAL == 0 \
- && TYPE_MODE (strip_array_types (TREE_TYPE (FIELD))) == DFmode) \
- ? MIN ((COMPUTED), 32) \
- : (COMPUTED))
+ ? 128: (COMPUTED))
#undef TOC_SECTION_ASM_OP
#define TOC_SECTION_ASM_OP \
Index: gcc/config/rs6000/linux64.h
===================================================================
--- gcc/config/rs6000/linux64.h (revision 233308)
+++ gcc/config/rs6000/linux64.h (working copy)
@@ -290,16 +290,10 @@ extern int dot_symbols;
#define PROFILE_HOOK(LABEL) \
do { if (TARGET_64BIT) output_profile_hook (LABEL); } while (0)
-/* PowerPC64 Linux word-aligns FP doubles when -malign-power is given. */
#undef ADJUST_FIELD_ALIGN
#define ADJUST_FIELD_ALIGN(FIELD, COMPUTED) \
(rs6000_special_adjust_field_align_p ((FIELD), (COMPUTED)) \
- ? 128 \
- : (TARGET_64BIT \
- && TARGET_ALIGN_NATURAL == 0 \
- && TYPE_MODE (strip_array_types (TREE_TYPE (FIELD))) == DFmode) \
- ? MIN ((COMPUTED), 32) \
- : (COMPUTED))
+ ? 128: (COMPUTED))
/* PowerPC64 Linux increases natural record alignment to doubleword if
the first field is an FP double, only if in power alignment mode. */
