From 81825e283f6cec28db73af9769602b953d683e3e Mon Sep 17 00:00:00 2001 From: Wilco Dijkstra Date: Thu, 16 Nov 2017 11:54:49 +0000 Subject: [PATCH] Canonicalize constant multiplies in division This patch implements some of the optimizations discussed in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71026. Canonicalize x / (C1 * y) into (x * C2) / y. This moves constant multiplies out of the RHS of a division in order to allow further simplifications (such as (C1 * x) / (C2 * y) -> (C3 * x) / y) and to enable more reciprocal CSEs. 2017-11-16 Wilco Dijkstra Jackson Woodruff gcc/ PR tree-optimization/71026 * match.pd: Canonicalize constant multiplies in division. gcc/testsuite/ PR tree-optimization/71026 * gcc.dg/cse_recip.c: New test. Co-Authored-By: Jackson Woodruff From-SVN: r254816 --- gcc/ChangeLog | 6 ++++++ gcc/match.pd | 21 ++++++++++----------- gcc/testsuite/ChangeLog | 6 ++++++ gcc/testsuite/gcc.dg/cse_recip.c | 12 ++++++++++++ 4 files changed, 34 insertions(+), 11 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/cse_recip.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index f9a429369d6..aaaa6389856 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2017-11-16 Wilco Dijkstra + Jackson Woodruff + + PR tree-optimization/71026 + * match.pd: Canonicalize constant multiplies in division. + 2017-11-16 Wilco Dijkstra * opts.c (default_options_table): Add OPT_fomit_frame_pointer entry. diff --git a/gcc/match.pd b/gcc/match.pd index 2557f08ad35..0e21a0d8d8f 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -344,10 +344,18 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (negate @0))) (if (flag_reciprocal_math) - /* Convert (A/B)/C to A/(B*C) */ + /* Convert (A/B)/C to A/(B*C). */ (simplify (rdiv (rdiv:s @0 @1) @2) - (rdiv @0 (mult @1 @2))) + (rdiv @0 (mult @1 @2))) + + /* Canonicalize x / (C1 * y) to (x * C2) / y. */ + (simplify + (rdiv @0 (mult:s @1 REAL_CST@2)) + (with + { tree tem = const_binop (RDIV_EXPR, type, build_one_cst (type), @2); } + (if (tem) + (rdiv (mult @0 { tem; } ) @1)))) /* Convert A/(B/C) to (A/B)*C */ (simplify @@ -633,15 +641,6 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (if (tem) (rdiv { tem; } @1))))) -/* Convert C1/(X*C2) into (C1/C2)/X */ -(simplify - (rdiv REAL_CST@0 (mult @1 REAL_CST@2)) - (if (flag_reciprocal_math) - (with - { tree tem = const_binop (RDIV_EXPR, type, @0, @2); } - (if (tem) - (rdiv { tem; } @1))))) - /* Simplify ~X & X as zero. */ (simplify (bit_and:c (convert? @0) (convert? (bit_not @0))) diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 2c3e979ce95..57bdc1c5ccc 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,9 @@ +2017-11-16 Wilco Dijkstra + Jackson Woodruff + + PR tree-optimization/71026 + * gcc.dg/cse_recip.c: New test. + 2017-11-16 Wilco Dijkstra * gcc.target/aarch64/lr_free_2.c: Fix test. diff --git a/gcc/testsuite/gcc.dg/cse_recip.c b/gcc/testsuite/gcc.dg/cse_recip.c new file mode 100644 index 00000000000..88cba9930c0 --- /dev/null +++ b/gcc/testsuite/gcc.dg/cse_recip.c @@ -0,0 +1,12 @@ +/* { dg-do compile } */ +/* { dg-options "-Ofast -fdump-tree-optimized-raw" } */ + +void +cse_recip (float x, float y, float *a) +{ + a[0] = y / (5 * x); + a[1] = y / (3 * x); + a[2] = y / x; +} + +/* { dg-final { scan-tree-dump-times "rdiv_expr" 1 "optimized" } } */ -- 2.30.2