From 17163cf43a6b6eec9aac44f6a4463dda54b8ed68 Mon Sep 17 00:00:00 2001 From: Xiretza Date: Wed, 8 Apr 2020 19:30:47 +0200 Subject: Add flooring modulo operator The $div and $mod cells use truncating division semantics (rounding towards 0), as defined by e.g. Verilog. Another rounding mode, flooring (rounding towards negative infinity), can be used in e.g. VHDL. The new $modfloor cell provides this flooring modulo (also known as "remainder" in several languages, but this name is ambiguous). This commit also fixes the handling of $mod in opt_expr, which was previously optimized as if it was $modfloor. --- kernel/calc.cc | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) (limited to 'kernel/calc.cc') diff --git a/kernel/calc.cc b/kernel/calc.cc index 4a4840771..38a529128 100644 --- a/kernel/calc.cc +++ b/kernel/calc.cc @@ -489,6 +489,7 @@ RTLIL::Const RTLIL::const_mul(const RTLIL::Const &arg1, const RTLIL::Const &arg2 return big2const(y, result_len >= 0 ? result_len : max(arg1.bits.size(), arg2.bits.size()), min(undef_bit_pos, 0)); } +// truncating division RTLIL::Const RTLIL::const_div(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len) { int undef_bit_pos = -1; @@ -502,6 +503,7 @@ RTLIL::Const RTLIL::const_div(const RTLIL::Const &arg1, const RTLIL::Const &arg2 return big2const(result_neg ? -(a / b) : (a / b), result_len >= 0 ? result_len : max(arg1.bits.size(), arg2.bits.size()), min(undef_bit_pos, 0)); } +// truncating modulo RTLIL::Const RTLIL::const_mod(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len) { int undef_bit_pos = -1; @@ -515,6 +517,29 @@ RTLIL::Const RTLIL::const_mod(const RTLIL::Const &arg1, const RTLIL::Const &arg2 return big2const(result_neg ? -(a % b) : (a % b), result_len >= 0 ? result_len : max(arg1.bits.size(), arg2.bits.size()), min(undef_bit_pos, 0)); } +RTLIL::Const RTLIL::const_modfloor(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len) +{ + int undef_bit_pos = -1; + BigInteger a = const2big(arg1, signed1, undef_bit_pos); + BigInteger b = const2big(arg2, signed2, undef_bit_pos); + if (b.isZero()) + return RTLIL::Const(RTLIL::State::Sx, result_len); + + BigInteger::Sign a_sign = a.getSign(); + BigInteger::Sign b_sign = b.getSign(); + a = a_sign == BigInteger::negative ? -a : a; + b = b_sign == BigInteger::negative ? -b : b; + BigInteger truncated = a_sign == BigInteger::negative ? -(a % b) : (a % b); + BigInteger modulo; + + if (truncated == 0 || (a_sign == b_sign)) { + modulo = truncated; + } else { + modulo = b_sign == BigInteger::negative ? truncated - b : truncated + b; + } + return big2const(modulo, result_len >= 0 ? result_len : max(arg1.bits.size(), arg2.bits.size()), min(undef_bit_pos, 0)); +} + RTLIL::Const RTLIL::const_pow(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len) { int undef_bit_pos = -1; -- cgit v1.2.3 From edd8ff2c0778d97808869488cc7394151456c4ca Mon Sep 17 00:00:00 2001 From: Xiretza Date: Tue, 21 Apr 2020 12:51:58 +0200 Subject: Add flooring division operator The $div and $mod cells use truncating division semantics (rounding towards 0), as defined by e.g. Verilog. Another rounding mode, flooring (rounding towards negative infinity), can be used in e.g. VHDL. The new $divfloor cell provides this flooring division. This commit also fixes the handling of $div in opt_expr, which was previously optimized as if it was $divfloor. --- kernel/calc.cc | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'kernel/calc.cc') diff --git a/kernel/calc.cc b/kernel/calc.cc index 38a529128..ae18809d3 100644 --- a/kernel/calc.cc +++ b/kernel/calc.cc @@ -517,6 +517,28 @@ RTLIL::Const RTLIL::const_mod(const RTLIL::Const &arg1, const RTLIL::Const &arg2 return big2const(result_neg ? -(a % b) : (a % b), result_len >= 0 ? result_len : max(arg1.bits.size(), arg2.bits.size()), min(undef_bit_pos, 0)); } +RTLIL::Const RTLIL::const_divfloor(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len) +{ + int undef_bit_pos = -1; + BigInteger a = const2big(arg1, signed1, undef_bit_pos); + BigInteger b = const2big(arg2, signed2, undef_bit_pos); + if (b.isZero()) + return RTLIL::Const(RTLIL::State::Sx, result_len); + + bool result_pos = (a.getSign() == BigInteger::negative) == (b.getSign() == BigInteger::negative); + a = a.getSign() == BigInteger::negative ? -a : a; + b = b.getSign() == BigInteger::negative ? -b : b; + BigInteger result; + + if (result_pos || a == 0) { + result = a / b; + } else { + // bigint division with negative numbers is wonky, make sure we only negate at the very end + result = -((a + b - 1) / b); + } + return big2const(result, result_len >= 0 ? result_len : max(arg1.bits.size(), arg2.bits.size()), min(undef_bit_pos, 0)); +} + RTLIL::Const RTLIL::const_modfloor(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len) { int undef_bit_pos = -1; -- cgit v1.2.3