diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 40fddc4007e5..f09c0a026388 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,16 @@ +2016-03-30 Michael Matz + Richard Biener + + PR ipa/12392 + * ipa-polymorphic-call.c (struct type_change_info): Change + speculative to an unsigned allowing to limit the work we do. + (csftc_abort_walking_p): New inline function.. + (check_stmt_for_type_change): Limit the number of may-defs + skipped for speculative devirtualization to + max-speculative-devirt-maydefs. + * params.def (max-speculative-devirt-maydefs): New param. + * doc/invoke.texi (--param max-speculative-devirt-maydefs): Document. + 2016-03-30 Mike Stump PR target/63890 diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index ed1ad6214b27..e9763d44d8d7 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -9601,6 +9601,11 @@ Enable emission of special debug stores within HSA kernels which are then read and reported by libgomp plugin. Generation of these stores is disabled by default, use @option{--param hsa-gen-debug-stores=1} to enable it. + +@item max-speculative-devirt-maydefs +The maximum number of may-defs we analyze when looking for a must-def +specifying the dynamic type of an object that invokes a virtual call +we may be able to devirtualize speculatively. @end table @end table diff --git a/gcc/ipa-polymorphic-call.c b/gcc/ipa-polymorphic-call.c index 842ca13cd06d..0ebbd4ae66da 100644 --- a/gcc/ipa-polymorphic-call.c +++ b/gcc/ipa-polymorphic-call.c @@ -38,6 +38,7 @@ along with GCC; see the file COPYING3. If not see #include "tree-dfa.h" #include "gimple-pretty-print.h" #include "tree-into-ssa.h" +#include "params.h" /* Return true when TYPE contains an polymorphic type and thus is interesting for devirtualization machinery. */ @@ -1094,14 +1095,15 @@ struct type_change_info tree known_current_type; HOST_WIDE_INT known_current_offset; + /* Set to nonzero if we possibly missed some dynamic type changes and we + should consider the set to be speculative. */ + unsigned speculative; + /* Set to true if dynamic type change has been detected. */ bool type_maybe_changed; /* Set to true if multiple types have been encountered. known_current_type must be disregarded in that case. */ bool multiple_types_encountered; - /* Set to true if we possibly missed some dynamic type changes and we should - consider the set to be speculative. */ - bool speculative; bool seen_unanalyzed_store; }; @@ -1338,6 +1340,19 @@ record_known_type (struct type_change_info *tci, tree type, HOST_WIDE_INT offset tci->type_maybe_changed = true; } + +/* The maximum number of may-defs we visit when looking for a must-def + that changes the dynamic type in check_stmt_for_type_change. Tuned + after the PR12392 testcase which unlimited spends 40% time within + these alias walks and 8% with the following limit. */ + +static inline bool +csftc_abort_walking_p (unsigned speculative) +{ + unsigned max = PARAM_VALUE (PARAM_MAX_SPECULATIVE_DEVIRT_MAYDEFS); + return speculative > max ? true : false; +} + /* Callback of walk_aliased_vdefs and a helper function for detect_type_change to check whether a particular statement may modify the virtual table pointer, and if possible also determine the new type of @@ -1384,15 +1399,15 @@ check_stmt_for_type_change (ao_ref *ao ATTRIBUTE_UNUSED, tree vdef, void *data) &size, &max_size, &reverse); if (size != max_size || max_size == -1) { - tci->speculative = true; - return false; + tci->speculative++; + return csftc_abort_walking_p (tci->speculative); } if (op && TREE_CODE (op) == MEM_REF) { if (!tree_fits_shwi_p (TREE_OPERAND (op, 1))) { - tci->speculative = true; - return false; + tci->speculative++; + return csftc_abort_walking_p (tci->speculative); } offset += tree_to_shwi (TREE_OPERAND (op, 1)) * BITS_PER_UNIT; @@ -1402,8 +1417,8 @@ check_stmt_for_type_change (ao_ref *ao ATTRIBUTE_UNUSED, tree vdef, void *data) ; else { - tci->speculative = true; - return false; + tci->speculative++; + return csftc_abort_walking_p (tci->speculative); } op = walk_ssa_copies (op); } @@ -1438,8 +1453,8 @@ check_stmt_for_type_change (ao_ref *ao ATTRIBUTE_UNUSED, tree vdef, void *data) fprintf (dump_file, " Function call may change dynamic type:"); print_gimple_stmt (dump_file, stmt, 0, 0); } - tci->speculative = true; - return false; + tci->speculative++; + return csftc_abort_walking_p (tci->speculative); } /* Check for inlined virtual table store. */ else if (noncall_stmt_may_be_vtbl_ptr_store (stmt)) @@ -1461,7 +1476,7 @@ check_stmt_for_type_change (ao_ref *ao ATTRIBUTE_UNUSED, tree vdef, void *data) if (dump_file) fprintf (dump_file, " Unanalyzed store may change type.\n"); tci->seen_unanalyzed_store = true; - tci->speculative = true; + tci->speculative++; } else record_known_type (tci, type, offset); @@ -1646,7 +1661,7 @@ ipa_polymorphic_call_context::get_dynamic_type (tree instance, tci.otr_type = otr_type; tci.type_maybe_changed = false; tci.multiple_types_encountered = false; - tci.speculative = false; + tci.speculative = 0; tci.seen_unanalyzed_store = false; walk_aliased_vdefs (&ao, gimple_vuse (stmt), check_stmt_for_type_change, diff --git a/gcc/params.def b/gcc/params.def index 9362c1588de8..dbff305b7f40 100644 --- a/gcc/params.def +++ b/gcc/params.def @@ -1203,6 +1203,12 @@ DEFPARAM (PARAM_HSA_GEN_DEBUG_STORES, "hsa-gen-debug-stores", "Level of hsa debug stores verbosity", 0, 0, 1) + +DEFPARAM (PARAM_MAX_SPECULATIVE_DEVIRT_MAYDEFS, + "max-speculative-devirt-maydefs", + "Maximum number of may-defs visited when devirtualizing " + "speculatively", 50, 0, 0) + /* Local variables: