From b9721bedf01ca1f536bbf13ba761333c6867bd29 Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Mon, 21 Dec 2020 02:15:55 +0000
Subject: cxxrtl: speed up bit repeats (sign extends, etc).

On Minerva SoC SRAM, depending on the compiler, this change improves
overall time by 4-7%.
---
 backends/cxxrtl/cxxrtl.h | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'backends/cxxrtl/cxxrtl.h')

diff --git a/backends/cxxrtl/cxxrtl.h b/backends/cxxrtl/cxxrtl.h
index 3c315c7df..0a6bcb849 100644
--- a/backends/cxxrtl/cxxrtl.h
+++ b/backends/cxxrtl/cxxrtl.h
@@ -317,6 +317,14 @@ struct value : public expr_base<value<Bits>> {
 		return sext_cast<NewBits>()(*this);
 	}
 
+	// Bit replication is far more efficient than the equivalent concatenation.
+	template<size_t Count>
+	CXXRTL_ALWAYS_INLINE
+	value<Bits * Count> repeat() const {
+		static_assert(Bits == 1, "repeat() is implemented only for 1-bit values");
+		return *this ? value<Bits * Count>().bit_not() : value<Bits * Count>();
+	}
+
 	// Operations with run-time parameters (offsets, amounts, etc).
 	//
 	// These operations are used for computations.
-- 
cgit v1.2.3