From: James Greenhalgh Date: Thu, 22 Jun 2017 08:39:04 +0000 (+0000) Subject: [Patch match.pd] Fold (A / (1 << B)) to (A >> B) X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=71f82be94fad1597696b14c325eed203b75dde70;p=gcc.git [Patch match.pd] Fold (A / (1 << B)) to (A >> B) For the testcase in the patch: unsigned long f2 (unsigned long a, int b) { unsigned long x = 1UL << b; return a / x; } We currently generate an unsigned division and a left shift, where we could instead generate a right shift. gcc/ 2017-06-21 James Greenhalgh * match.pd (A / (1 << B) -> A >> B): New. * generic-match-head.c: Include optabs-tree.h. * gimple-match-head.c: Likewise. * optabs-tree.h (target_supports_op_p): New. * optabs-tree.c (target_supports_op_p): New. gcc/testsuite/ 2017-06-21 James Greenhalgh * gcc.dg/tree-ssa/forwprop-37.c: New. From-SVN: r249502 --- diff --git a/gcc/ChangeLog b/gcc/ChangeLog index c056ae4609b..9b150a48645 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,11 @@ +2017-06-22 James Greenhalgh + + * match.pd (A / (1 << B) -> A >> B): New. + * generic-match-head.c: Include optabs-tree.h. + * gimple-match-head.c: Likewise. + * optabs-tree.h (target_supports_op_p): New. + * optabs-tree.c (target_supports_op_p): New. + 2017-06-22 Rainer Orth * configure.ac (gcc_cv_ld_static_dynamic): Also check stderr for diff --git a/gcc/generic-match-head.c b/gcc/generic-match-head.c index 0c0d1824933..4504401fa8a 100644 --- a/gcc/generic-match-head.c +++ b/gcc/generic-match-head.c @@ -33,6 +33,7 @@ along with GCC; see the file COPYING3. If not see #include "builtins.h" #include "case-cfn-macros.h" #include "gimplify.h" +#include "optabs-tree.h" /* Routine to determine if the types T1 and T2 are effectively diff --git a/gcc/gimple-match-head.c b/gcc/gimple-match-head.c index e7e9839a4b8..5f6aa273b96 100644 --- a/gcc/gimple-match-head.c +++ b/gcc/gimple-match-head.c @@ -39,6 +39,7 @@ along with GCC; see the file COPYING3. If not see #include "internal-fn.h" #include "case-cfn-macros.h" #include "gimplify.h" +#include "optabs-tree.h" /* Forward declarations of the private auto-generated matchers. diff --git a/gcc/match.pd b/gcc/match.pd index 7bd26763826..a4cae113bc8 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -161,6 +161,18 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (op @0 integer_onep) (non_lvalue @0))) +/* (A / (1 << B)) -> (A >> B). + Only for unsigned A. For signed A, this would not preserve rounding + toward zero. + For example: (-1 / ( 1 << B)) != -1 >> B. */ +(simplify + (trunc_div @0 (lshift integer_onep@1 @2)) + (if ((TYPE_UNSIGNED (type) || tree_expr_nonnegative_p (@0)) + && (!VECTOR_TYPE_P (type) + || target_supports_op_p (type, RSHIFT_EXPR, optab_vector) + || target_supports_op_p (type, RSHIFT_EXPR, optab_scalar))) + (rshift @0 @2))) + /* Preserve explicit divisions by 0: the C++ front-end wants to detect undefined behavior in constexpr evaluation, and assuming that the division traps enables better optimizations than these anyway. */ diff --git a/gcc/optabs-tree.c b/gcc/optabs-tree.c index 4bb54ba4382..c183b14c819 100644 --- a/gcc/optabs-tree.c +++ b/gcc/optabs-tree.c @@ -376,3 +376,18 @@ init_tree_optimization_optabs (tree optnode) ggc_free (tmp_optabs); } } + +/* Return TRUE if the target has support for vector right shift of an + operand of type TYPE. If OT_TYPE is OPTAB_DEFAULT, check for existence + of a shift by either a scalar or a vector. Otherwise, check only + for a shift that matches OT_TYPE. */ + +bool +target_supports_op_p (tree type, enum tree_code code, + enum optab_subtype ot_subtype) +{ + optab ot = optab_for_tree_code (code, type, ot_subtype); + return (ot != unknown_optab + && optab_handler (ot, TYPE_MODE (type)) != CODE_FOR_nothing); +} + diff --git a/gcc/optabs-tree.h b/gcc/optabs-tree.h index d0b27e0e2f7..52e842bfb61 100644 --- a/gcc/optabs-tree.h +++ b/gcc/optabs-tree.h @@ -41,5 +41,7 @@ bool supportable_convert_operation (enum tree_code, tree, tree, tree *, bool expand_vec_cmp_expr_p (tree, tree, enum tree_code); bool expand_vec_cond_expr_p (tree, tree, enum tree_code); void init_tree_optimization_optabs (tree); +bool target_supports_op_p (tree, enum tree_code, + enum optab_subtype = optab_default); #endif diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 050e37defdf..497c4b87622 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,7 @@ +2017-06-22 James Greenhalgh + + * gcc.dg/tree-ssa/forwprop-37.c: New. + 2017-06-22 Richard Biener * gcc.dg/vect/pr65947-14.c: Fix missing brace. diff --git a/gcc/testsuite/gcc.dg/tree-ssa/forwprop-37.c b/gcc/testsuite/gcc.dg/tree-ssa/forwprop-37.c new file mode 100644 index 00000000000..dec826c76bd --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/forwprop-37.c @@ -0,0 +1,25 @@ +/* { dg-do compile } */ +/* { dg-options "-O -fdump-tree-forwprop1-raw" } */ + +unsigned int +f1 (unsigned int a, unsigned int b) +{ + unsigned int x = 1U << b; + return a / x; +} + +unsigned long +f2 (unsigned long a, int b) +{ + unsigned long x = 1UL << b; + return a / x; +} + +unsigned long long +f3 (unsigned long long a, int b) +{ + unsigned long long x = 1ULL << b; + return a / x; +} + +/* { dg-final { scan-tree-dump-not "trunc_div_expr" "forwprop1" } } */