On Wed, Mar 9, 2016 at 6:54 PM, Alan Lawrence <alan.lawre...@foss.arm.com> wrote: > On 07/03/16 11:02, Alan Lawrence wrote: >> >> On 04/03/16 13:27, Richard Biener wrote: >>> >>> I think to make it work with LTO you need to mark it 'Optimization'. >>> Also it's about >>> arrays so maybe >>> >>> 'Assume common declarations may be overridden with ones with a larger >>> trailing array' >>> >>> also if we document it here we should eventually document it in >>> invoke.texi. >>> >>> Not sure if "unknown commons" is a good term, maybe "unconstrained >>> commons" instead? >> >> >> All done; I doubt there is really a good word, unconstrained seems as good >> as >> any. I've reused much the same wording in invoke.texi, unless you think >> there >> is more to add. >> >> On 04/03/16 13:33, Jakub Jelinek wrote: >>> >>> Also, isn't the *.opt description line supposed to end with a full stop? >> >> >> Ah, yes, thanks. >> >> Is this version OK for trunk? >> >> gcc/ChangeLog: >> >> DATE Alan Lawrence <alan.lawre...@arm.com> >> Jakub Jelinek <ja...@redhat.com> >> >> * common.opt (funconstrained-commons, >> flag_unconstrained_commons): New. >> * tree.c (array_at_struct_end_p): Do not limit to size of decl >> for >> DECL_COMMONS if flag_unconstrained_commons is set. >> * tree-dfa.c (get_ref_base_and_extent): Likewise. > > > And add to that > * doc/invoke.texi (Optimize Options): Add -funconstrained-commons. > (funconstrained-commons): Document.
Ok. Richard. > Thanks, > Alan > >> >> gcc/testsuite/ChangeLog: >> >> * gfortran.dg/unconstrained_commons.f: New. >> --- >> gcc/common.opt | 5 +++++ >> gcc/doc/invoke.texi | 8 +++++++- >> gcc/testsuite/gfortran.dg/unconstrained_commons.f | 20 >> ++++++++++++++++++++ >> gcc/tree-dfa.c | 15 ++++++++++++++- >> gcc/tree.c | 6 ++++-- >> 5 files changed, 50 insertions(+), 4 deletions(-) >> create mode 100644 gcc/testsuite/gfortran.dg/unconstrained_commons.f >> >> diff --git a/gcc/common.opt b/gcc/common.opt >> index 520fa9c..bbf79ef 100644 >> --- a/gcc/common.opt >> +++ b/gcc/common.opt >> @@ -2451,6 +2451,11 @@ fsplit-paths >> Common Report Var(flag_split_paths) Init(0) Optimization >> Split paths leading to loop backedges. >> >> +funconstrained-commons >> +Common Var(flag_unconstrained_commons) Optimization >> +Assume common declarations may be overridden with ones with a larger >> +trailing array. >> + >> funit-at-a-time >> Common Report Var(flag_unit_at_a_time) Init(1) >> Compile whole compilation unit at a time. >> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi >> index 0a2a6f4..68933a1 100644 >> --- a/gcc/doc/invoke.texi >> +++ b/gcc/doc/invoke.texi >> @@ -407,7 +407,7 @@ Objective-C and Objective-C++ Dialects}. >> -ftree-parallelize-loops=@var{n} -ftree-pre -ftree-partial-pre >> -ftree-pta @gol >> -ftree-reassoc -ftree-sink -ftree-slsr -ftree-sra @gol >> -ftree-switch-conversion -ftree-tail-merge -ftree-ter @gol >> --ftree-vectorize -ftree-vrp @gol >> +-ftree-vectorize -ftree-vrp -funconstrained-commons @gol >> -funit-at-a-time -funroll-all-loops -funroll-loops @gol >> -funsafe-loop-optimizations -funsafe-math-optimizations -funswitch-loops >> @gol >> -fipa-ra -fvariable-expansion-in-unroller -fvect-cost-model -fvpt @gol >> @@ -6659,6 +6659,12 @@ the loop optimizer itself cannot prove that these >> assumptions are valid. >> If you use @option{-Wunsafe-loop-optimizations}, the compiler warns you >> if it finds this kind of loop. >> >> +@item -funconstrained-commons >> +@opindex funconstrained-commons >> +This option tells the compiler that variables declared in common blocks >> +(e.g. Fortran) may later be overridden with longer trailing arrays. This >> +prevents certain optimizations that depend on knowing the array bounds. >> + >> @item -fcrossjumping >> @opindex fcrossjumping >> Perform cross-jumping transformation. >> diff --git a/gcc/testsuite/gfortran.dg/unconstrained_commons.f >> b/gcc/testsuite/gfortran.dg/unconstrained_commons.f >> new file mode 100644 >> index 0000000..f9fc471 >> --- /dev/null >> +++ b/gcc/testsuite/gfortran.dg/unconstrained_commons.f >> @@ -0,0 +1,20 @@ >> +! { dg-do compile } >> +! { dg-options "-O3 -funconstrained-commons -fdump-tree-dom2-details" } >> + >> +! Test for PR69368: a single-element array in a common block, which will >> be >> +! overridden with a larger size at link time (contrary to language spec). >> +! Dominator opts considers accesses to differently-computed elements of X >> as >> +! equivalent, unless -funconstrained-commons is passed in. >> + SUBROUTINE FOO >> + IMPLICIT DOUBLE PRECISION (X) >> + INTEGER J >> + COMMON /MYCOMMON / X(1) >> + DO 10 J=1,1024 >> + X(J+1)=X(J+7) >> + 10 CONTINUE >> + RETURN >> + END >> +! { dg-final { scan-tree-dump-not "FIND" "dom2" } } >> +! We should retain both a read and write of mycommon.x. >> +! { dg-final { scan-tree-dump-times " _\[0-9\]+ = >> mycommon\\.x\\\[_\[0-9\]+\\\];" 1 "dom2" } } >> +! { dg-final { scan-tree-dump-times " mycommon\\.x\\\[_\[0-9\]+\\\] = >> _\[0-9\]+;" 1 "dom2" } } >> diff --git a/gcc/tree-dfa.c b/gcc/tree-dfa.c >> index 0e98056..f133abc 100644 >> --- a/gcc/tree-dfa.c >> +++ b/gcc/tree-dfa.c >> @@ -612,9 +612,22 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT >> *poffset, >> >> if (DECL_P (exp)) >> { >> + if (flag_unconstrained_commons >> + && TREE_CODE (exp) == VAR_DECL && DECL_COMMON (exp)) >> + { >> + tree sz_tree = TYPE_SIZE (TREE_TYPE (exp)); >> + /* If size is unknown, or we have read to the end, assume there >> + may be more to the structure than we are told. */ >> + if (TREE_CODE (TREE_TYPE (exp)) == ARRAY_TYPE >> + || (seen_variable_array_ref >> + && (sz_tree == NULL_TREE >> + || TREE_CODE (sz_tree) != INTEGER_CST >> + || (bit_offset + maxsize == wi::to_offset >> (sz_tree))))) >> + maxsize = -1; >> + } >> /* If maxsize is unknown adjust it according to the size of the >> base decl. */ >> - if (maxsize == -1 >> + else if (maxsize == -1 >> && DECL_SIZE (exp) >> && TREE_CODE (DECL_SIZE (exp)) == INTEGER_CST) >> maxsize = wi::to_offset (DECL_SIZE (exp)) - bit_offset; >> diff --git a/gcc/tree.c b/gcc/tree.c >> index 07cb9d9..9179b37 100644 >> --- a/gcc/tree.c >> +++ b/gcc/tree.c >> @@ -12957,8 +12957,10 @@ array_at_struct_end_p (tree ref) >> } >> >> /* If the reference is based on a declared entity, the size of the >> array >> - is constrained by its given domain. */ >> - if (DECL_P (ref)) >> + is constrained by its given domain. (Do not trust commons >> PR/69368). */ >> + if (DECL_P (ref) >> + && !(flag_unconstrained_commons >> + && TREE_CODE (ref) == VAR_DECL && DECL_COMMON (ref))) >> return false; >> >> return true; >> >