70 lines
2.5 KiB
Diff
70 lines
2.5 KiB
Diff
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From dbf3dc75888623e9d4bb7cc5e9c30caa9b24ffe7 Mon Sep 17 00:00:00 2001
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From: Bu Le <bule1@huawei.com>
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Date: Thu, 12 Mar 2020 22:39:12 +0000
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Subject: [PATCH] aarch64: Add --params to control the number of recip steps
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[PR94154]
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-mlow-precision-div hard-coded the number of iterations to 2 for double
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and 1 for float. This patch adds a --param to control the number.
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2020-03-13 Bu Le <bule1@huawei.com>
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gcc/
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PR target/94154
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* config/aarch64/aarch64.opt (-param=aarch64-float-recp-precision=)
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(-param=aarch64-double-recp-precision=): New options.
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* doc/invoke.texi: Document them.
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* config/aarch64/aarch64.c (aarch64_emit_approx_div): Use them
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instead of hard-coding the choice of 1 for float and 2 for double.
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---
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gcc/ChangeLog | 9 +++++++++
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gcc/config/aarch64/aarch64.c | 8 +++++---
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gcc/config/aarch64/aarch64.opt | 9 +++++++++
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gcc/doc/invoke.texi | 11 +++++++++++
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4 files changed, 34 insertions(+), 3 deletions(-)
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diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
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index c320d5ba51d..2c81f86dd2a 100644
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--- a/gcc/config/aarch64/aarch64.c
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+++ b/gcc/config/aarch64/aarch64.c
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@@ -12911,10 +12911,12 @@ aarch64_emit_approx_div (rtx quo, rtx num, rtx den)
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/* Iterate over the series twice for SF and thrice for DF. */
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int iterations = (GET_MODE_INNER (mode) == DFmode) ? 3 : 2;
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- /* Optionally iterate over the series once less for faster performance,
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- while sacrificing the accuracy. */
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+ /* Optionally iterate over the series less for faster performance,
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+ while sacrificing the accuracy. The default is 2 for DF and 1 for SF. */
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if (flag_mlow_precision_div)
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- iterations--;
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+ iterations = (GET_MODE_INNER (mode) == DFmode
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+ ? PARAM_VALUE (PARAM_AARCH64_DOUBLE_RECP_PRECISION)
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+ : PARAM_VALUE (PARAM_AARCH64_FLOAT_RECP_PRECISION));
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/* Iterate over the series to calculate the approximate reciprocal. */
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rtx xtmp = gen_reg_rtx (mode);
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--- a/gcc/params.def 2020-04-15 17:24:31.984000000 +0800
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+++ b/gcc/params.def 2020-04-15 16:59:21.752000000 +0800
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@@ -1420,6 +1414,17 @@ DEFPARAM(PARAM_SSA_NAME_DEF_CHAIN_LIMIT,
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"a value.",
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512, 0, 0)
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+DEFPARAM(PARAM_AARCH64_FLOAT_RECP_PRECISION,
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+ "aarch64-float-recp-precision",
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+ "The number of Newton iterations for calculating the reciprocal "
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+ "for float type. ",
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+ 1, 1, 5)
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+
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+DEFPARAM(PARAM_AARCH64_DOUBLE_RECP_PRECISION,
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+ "aarch64-double-recp-precision",
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+ "The number of Newton iterations for calculating the reciprocal "
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+ "for double type.",
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+ 2, 1, 5)
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/*
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Local variables:
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--
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2.18.2
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