Uli, Bootstrap on AIX has been broken because of the generic GCC latent bug that seems to be popping up on various architectures. I could not bootstrap GCC from 11 Jul to 14 Jul. I was able to bootstrap on 15 Jul. I want to ensure that bootstrap is functioning consistently before approving these and the other ABI changes so that I can confirm that the patches don't accidentally affect AIX.
Thanks, David On Mon, Jul 14, 2014 at 2:54 PM, Ulrich Weigand <uweig...@de.ibm.com> wrote: > Hello, > > this patch updates the prior version: > https://gcc.gnu.org/ml/gcc-patches/2014-07/msg00634.html > to add a -Wpsabi note as discussed. > > Note that the warning triggers whenever type is encountered whose alignment > *requirement* changes due to this patch. In some cases, this does not > actually > change the ABI of a given function call since the argument happened to be > already aligned for the higher requirement as well. > > Except for a few cases in the ABI compat suite (as expected), this note > triggers in three test cases: > > In the ELFv1 ABI only: > gcc.c-torture/compile/20040709-1.c:7:1: note: the ABI of passing aggregates > with 16-byte alignment has changed in GCC 4.10 > union foo { > long double ld; > } bar; > > Note that this union counts as homogeneous aggregate according to > the ELFv2 ABI, so it is treated the same before and after this patch > (i.e. aligned to 8 bytes). > > In the ELFv1 ABI, however, this union does *not* count as a single-element > float struct (because its mode is TImode, not TFmode, since common code > does the latter only for single-element structs, not unions). Therefore, > this union used to be 8-byte aligned but is now 16-byte aligned. > > In both the ELFv1 and ELFv2 ABIs: > gcc.dg/pr32293.c:46:1: note: the ABI of passing aggregates with 16-byte > alignment has changed in GCC 4.10 > typedef > __attribute__ ((aligned(16))) > struct { > UINT64 w[2]; > } UINT128; > > g++.dg/abi/param2.C:9:1: note: the ABI of passing aggregates with 16-byte > alignment has changed in GCC 4.10 > struct S { union {} a; } __attribute__((aligned)); > > In both cases, we have a struct of size 16 bytes (in the second case due to > alignment padding) and alignment requirement 16 bytes, which is recognized > as TImode and not BLKmode by common code, and thus used to be 8-byte aligned > but is now 16-byte aligned. > > The tests still PASS since the dg-test infrastructure prunes all informational > messages from the GCC output. > > Based on the discussion after the previous patch submission, the patch > leaves the Darwin ABI unchanged. > > Tested on powerpc64-linux and powerpc64le-linux. > > OK for mainline? > > Bye, > Ulrich > > > gcc/ChangeLog: > > * config/rs6000/rs6000.c (rs6000_function_arg_boundary): In the AIX > and ELFv2 ABI, do not use the "mode == BLKmode" check to test for > aggregate types. Instead, *all* aggregate types, except for single- > element or homogeneous float/vector aggregates, are quadword-aligned > if required by their type alignment. Issue -Wpsabi note when a type > is now treated differently than before. > > gcc/testsuite/ChangLog: > > * gcc.target/powerpc/ppc64-abi-warn-2.c: New test. > > > Index: gcc/config/rs6000/rs6000.c > =================================================================== > --- gcc/config/rs6000/rs6000.c (revision 212147) > +++ gcc/config/rs6000/rs6000.c (working copy) > @@ -9182,14 +9182,48 @@ > || (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" > + " has changed in GCC 4.10", > + (int) TYPE_ALIGN (type) / BITS_PER_UNIT); > + } > + } > + > + if (aggregate_p) > + 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/testsuite/gcc.target/powerpc/ppc64-abi-warn-2.c > =================================================================== > --- /dev/null > +++ gcc/testsuite/gcc.target/powerpc/ppc64-abi-warn-2.c (revision 0) > @@ -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 has changed" } */ > +{ > +} > + > -- > Dr. Ulrich Weigand > GNU/Linux compilers and toolchain > ulrich.weig...@de.ibm.com >
