From 71017a7b7837a4eeb1d1c0b2b155c6567f4f3d95 Mon Sep 17 00:00:00 2001 From: Alan Lawrence Date: Thu, 10 Mar 2016 12:19:45 +0000 Subject: [PATCH] Add -funconstrained-commons to work around PR/69368 (and others) in SPEC2006 gcc/: * 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. * doc/invoke.texi (Optimize Options): Add -funconstrained-commons. (funconstrained-commons): Document. gcc/testsuite: * gfortran.dg/unconstrained_commons.f: New. Co-Authored-By: Jakub Jelinek From-SVN: r234106 --- gcc/ChangeLog | 10 ++++++++++ gcc/common.opt | 5 +++++ gcc/doc/invoke.texi | 8 +++++++- gcc/testsuite/ChangeLog | 4 ++++ .../gfortran.dg/unconstrained_commons.f | 20 +++++++++++++++++++ gcc/tree-dfa.c | 15 +++++++++++++- gcc/tree.c | 6 ++++-- 7 files changed, 64 insertions(+), 4 deletions(-) create mode 100644 gcc/testsuite/gfortran.dg/unconstrained_commons.f diff --git a/gcc/ChangeLog b/gcc/ChangeLog index ce244b190803..b6db5dec92e4 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,13 @@ +2016-03-10 Alan Lawrence + Jakub Jelinek + + * 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. + * doc/invoke.texi (Optimize Options): Add -funconstrained-commons. + (funconstrained-commons): Document. + 2016-03-10 Christophe Lyon * config/aarch64/t-aarch64 (OPTIONS_H_EXTRA): Add diff --git a/gcc/common.opt b/gcc/common.opt index e91f2257e55d..1c8cc8ede8f3 100644 --- a/gcc/common.opt +++ b/gcc/common.opt @@ -2458,6 +2458,11 @@ 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 9580c10fc451..99ac11b77140 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -408,7 +408,7 @@ 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 @@ -6699,6 +6699,12 @@ 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/ChangeLog b/gcc/testsuite/ChangeLog index 9ae7afd6d9b5..f2ed2aba119a 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,7 @@ +2016-03-10 Alan Lawrence + + * gfortran.dg/unconstrained_commons.f: New. + 2016-03-10 Alan Modra * gcc.dg/pr69195.c: New. diff --git a/gcc/testsuite/gfortran.dg/unconstrained_commons.f b/gcc/testsuite/gfortran.dg/unconstrained_commons.f new file mode 100644 index 000000000000..f9fc471e55ad --- /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 0e9805663b2f..f133abc79bda 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 b8333d45d047..7d0cb035b233 100644 --- a/gcc/tree.c +++ b/gcc/tree.c @@ -12952,8 +12952,10 @@ 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;