From 506678c708290e6962afaed113f4c98929f15baa Mon Sep 17 00:00:00 2001
From: Michael Beck <beck@ipd.info.uni-karlsruhe.de>
Date: Wed, 3 Feb 2010 22:15:45 +0000
Subject: [PATCH] Add get_tarval_lowest_bit() and get_tarval_popcnt(), expand
 some documentation.

[r27036]
---
 include/libfirm/tv.h | 24 ++++++++++++++++++++---
 ir/tv/tv.c           | 45 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+), 3 deletions(-)

diff --git a/include/libfirm/tv.h b/include/libfirm/tv.h
index 6433d7e91..5b3cdda14 100644
--- a/include/libfirm/tv.h
+++ b/include/libfirm/tv.h
@@ -716,10 +716,10 @@ char *get_tarval_bitpattern(tarval *tv);
  *
  * To query a 32bit value the following code can be used:
  *
- * val0 = tarval_sub_bits(tv, 0);
+ * val0 = tarval_sub_bits(tv, 0);  <- lowest bits
  * val1 = tarval_sub_bits(tv, 1);
  * val2 = tarval_sub_bits(tv, 2);
- * val3 = tarval_sub_bits(tv, 3);
+ * val3 = tarval_sub_bits(tv, 3);  <- highest bits
  *
  * Because this is the bit representation of the target machine, only the following
  * operations are legal on the result:
@@ -728,7 +728,7 @@ char *get_tarval_bitpattern(tarval *tv);
  * - bitwise logical operations to select/mask bits
  *
  * @param tv        the tarval
- * @param byte_ofs  the byte offset
+ * @param byte_ofs  the byte offset from lower to higher
  *
  * @note
  *   The result of this function is undefined if the mode is neither integer nor float.
@@ -743,6 +743,24 @@ unsigned char get_tarval_sub_bits(tarval *tv, unsigned byte_ofs);
  */
 int tarval_is_single_bit(tarval *tv);
 
+/**
+ * Return the number of set bits in a given (integer) tarval.
+ *
+ * @param tv    the tarval
+ *
+ * @return number of set bits or -1 on error
+ */
+int get_tarval_popcnt(tarval *tv);
+
+/**
+ * Return the number of the lowest set bit in a given (integer) tarval.
+ *
+ * @param tv    the tarval
+ *
+ * @return number of lowest set bit or -1 on error
+ */
+int get_tarval_lowest_bit(tarval *tv);
+
 /**
  * Output a tarval to a string buffer.
  *
diff --git a/ir/tv/tv.c b/ir/tv/tv.c
index 30b400043..1c2ca0f11 100644
--- a/ir/tv/tv.c
+++ b/ir/tv/tv.c
@@ -41,6 +41,7 @@
 #endif
 #include <stdlib.h>
 
+#include "bitfiddle.h"
 #include "tv_t.h"
 #include "set.h"
 #include "entity_t.h"
@@ -1624,6 +1625,50 @@ int tarval_is_single_bit(tarval *tv) {
 	return bits;
 }
 
+/*
+ * Return the number of set bits in a given (integer) tarval.
+ */
+int get_tarval_popcnt(tarval *tv)
+{
+	int i, l;
+	int bits;
+
+	if (!tv || tv == tarval_bad) return -1;
+	if (! mode_is_int(tv->mode)) return -1;
+
+	l = get_mode_size_bytes(tv->mode);
+	for (bits = 0, i = l - 1; i >= 0; --i) {
+		unsigned char v = get_tarval_sub_bits(tv, (unsigned)i);
+
+		bits += popcnt(v);
+	}
+	return bits;
+}
+
+/**
+ * Return the number of the lowest set bit in a given (integer) tarval.
+ *
+ * @param tv    the tarval
+ *
+ * @return number of lowest set bit or -1 on error
+ */
+int get_tarval_lowest_bit(tarval *tv)
+{
+	int i, l;
+
+	if (!tv || tv == tarval_bad) return -1;
+	if (! mode_is_int(tv->mode)) return -1;
+
+	l = get_mode_size_bytes(tv->mode);
+	for (i = 0; i < l; ++i) {
+		unsigned char v = get_tarval_sub_bits(tv, (unsigned)i);
+
+		if (v)
+			return ntz(v) + i * 8;
+	}
+	return -1;
+}
+
 /*
  * Returns non-zero if the mantissa of a floating point IEEE-754
  * tarval is zero (i.e. 1.0Exxx)
-- 
2.20.1