From da330a8a7b39b1d20ca9647c15dbbfd7cbac127d Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Fri, 8 Mar 2019 02:10:34 +0100
Subject: [PATCH] Implement Int#{leading,trailing}_zeros_count
---
spec/std/big/big_int_spec.cr | 4 ++
spec/std/int_spec.cr | 16 +++++++
src/big/big_int.cr | 4 ++
src/big/lib_gmp.cr | 2 +
src/int.cr | 93 ++++++++++++++++++++++++++++++++++++
src/intrinsics.cr | 12 +++++
6 files changed, 131 insertions(+)
diff --git a/spec/std/big/big_int_spec.cr b/spec/std/big/big_int_spec.cr
index ccfcdd4466d5..497a2dbff8fc 100644
--- a/spec/std/big/big_int_spec.cr
+++ b/spec/std/big/big_int_spec.cr
@@ -326,6 +326,10 @@ describe "BigInt" do
5.to_big_i.popcount.should eq(2)
end
+ it "#trailing_zeros_count" do
+ "00000000000000001000000000001000".to_big_i(base: 2).trailing_zeros_count.should eq(3)
+ end
+
it "#hash" do
b1 = 5.to_big_i
b2 = 5.to_big_i
diff --git a/spec/std/int_spec.cr b/spec/std/int_spec.cr
index 0a1c5abf4db2..f0d71f460d12 100644
--- a/spec/std/int_spec.cr
+++ b/spec/std/int_spec.cr
@@ -646,6 +646,22 @@ describe "Int" do
it { 18446744073709551615_u64.popcount.should eq(64) }
end
+ describe "#leading_zeros_count" do
+ {% for width in %w(8 16 32 64).map(&.id) %}
+ it { -1_i{{width}}.leading_zeros_count.should eq(0) }
+ it { 0_i{{width}}.leading_zeros_count.should eq({{width}}) }
+ it { 0_u{{width}}.leading_zeros_count.should eq({{width}}) }
+ {% end %}
+ end
+
+ describe "#trailing_zeros_count" do
+ {% for width in %w(8 16 32 64).map(&.id) %}
+ it { -2_i{{width}}.trailing_zeros_count.should eq(1) }
+ it { 2_i{{width}}.trailing_zeros_count.should eq(1) }
+ it { 2_u{{width}}.trailing_zeros_count.should eq(1) }
+ {% end %}
+ end
+
it "compares signed vs. unsigned integers" do
signed_ints = [Int8::MAX, Int16::MAX, Int32::MAX, Int64::MAX, Int8::MIN, Int16::MIN, Int32::MIN, Int64::MIN, 0_i8, 0_i16, 0_i32, 0_i64]
unsigned_ints = [UInt8::MAX, UInt16::MAX, UInt32::MAX, UInt64::MAX, 0_u8, 0_u16, 0_u32, 0_u64]
diff --git a/src/big/big_int.cr b/src/big/big_int.cr
index 8b0b71533f51..d3430bdf2d54 100644
--- a/src/big/big_int.cr
+++ b/src/big/big_int.cr
@@ -385,6 +385,10 @@ struct BigInt < Int
LibGMP.popcount(self)
end
+ def trailing_zeros_count
+ LibGMP.scan1(self, 0)
+ end
+
def to_i
to_i32
end
diff --git a/src/big/lib_gmp.cr b/src/big/lib_gmp.cr
index 6104825dbbb6..59c4ee464f7b 100644
--- a/src/big/lib_gmp.cr
+++ b/src/big/lib_gmp.cr
@@ -93,6 +93,8 @@ lib LibGMP
# # Logic
fun popcount = __gmpz_popcount(op : MPZ*) : BitcntT
+ fun scan0 = __gmpz_scan0(op : MPZ*, starting_bit : BitcntT) : BitcntT
+ fun scan1 = __gmpz_scan1(op : MPZ*, starting_bit : BitcntT) : BitcntT
# # Comparison
diff --git a/src/int.cr b/src/int.cr
index 64758aa4c82b..d78e151eea18 100644
--- a/src/int.cr
+++ b/src/int.cr
@@ -542,6 +542,9 @@ struct Int
# ```
abstract def popcount
+ # Returns the number of trailing `0`-bits.
+ abstract def trailing_zeros_count
+
private class TimesIterator(T)
include Iterator(T)
@@ -629,6 +632,15 @@ struct Int8
Intrinsics.popcount8(self)
end
+ # Returns the number of leading `0`-bits.
+ def leading_zeros_count
+ Intrinsics.countleading8(self, false)
+ end
+
+ def trailing_zeros_count
+ Intrinsics.counttrailing8(self, false)
+ end
+
def clone
self
end
@@ -656,6 +668,15 @@ struct Int16
Intrinsics.popcount16(self)
end
+ # Returns the number of leading `0`-bits.
+ def leading_zeros_count
+ Intrinsics.countleading16(self, false)
+ end
+
+ def trailing_zeros_count
+ Intrinsics.counttrailing16(self, false)
+ end
+
def clone
self
end
@@ -683,6 +704,15 @@ struct Int32
Intrinsics.popcount32(self)
end
+ # Returns the number of leading `0`-bits.
+ def leading_zeros_count
+ Intrinsics.countleading32(self, false)
+ end
+
+ def trailing_zeros_count
+ Intrinsics.counttrailing32(self, false)
+ end
+
def clone
self
end
@@ -710,6 +740,15 @@ struct Int64
Intrinsics.popcount64(self)
end
+ # Returns the number of leading `0`-bits.
+ def leading_zeros_count
+ Intrinsics.countleading64(self, false)
+ end
+
+ def trailing_zeros_count
+ Intrinsics.counttrailing64(self, false)
+ end
+
def clone
self
end
@@ -739,6 +778,15 @@ struct Int128
Intrinsics.popcount128(self)
end
+ # Returns the number of leading `0`-bits.
+ def leading_zeros_count
+ Intrinsics.countleading128(self, false)
+ end
+
+ def trailing_zeros_count
+ Intrinsics.counttrailing128(self, false)
+ end
+
def clone
self
end
@@ -766,6 +814,15 @@ struct UInt8
Intrinsics.popcount8(self)
end
+ # Returns the number of leading `0`-bits.
+ def leading_zeros_count
+ Intrinsics.countleading8(self, false)
+ end
+
+ def trailing_zeros_count
+ Intrinsics.counttrailing8(self, false)
+ end
+
def clone
self
end
@@ -793,6 +850,15 @@ struct UInt16
Intrinsics.popcount16(self)
end
+ # Returns the number of leading `0`-bits.
+ def leading_zeros_count
+ Intrinsics.countleading16(self, false)
+ end
+
+ def trailing_zeros_count
+ Intrinsics.counttrailing16(self, false)
+ end
+
def clone
self
end
@@ -820,6 +886,15 @@ struct UInt32
Intrinsics.popcount32(self)
end
+ # Returns the number of leading `0`-bits.
+ def leading_zeros_count
+ Intrinsics.countleading32(self, false)
+ end
+
+ def trailing_zeros_count
+ Intrinsics.counttrailing32(self, false)
+ end
+
def clone
self
end
@@ -847,6 +922,15 @@ struct UInt64
Intrinsics.popcount64(self)
end
+ # Returns the number of leading `0`-bits.
+ def leading_zeros_count
+ Intrinsics.countleading64(self, false)
+ end
+
+ def trailing_zeros_count
+ Intrinsics.counttrailing64(self, false)
+ end
+
def clone
self
end
@@ -875,6 +959,15 @@ struct UInt128
Intrinsics.popcount128(self)
end
+ # Returns the number of leading `0`-bits.
+ def leading_zeros_count
+ Intrinsics.countleading128(self, false)
+ end
+
+ def trailing_zeros_count
+ Intrinsics.counttrailing128(self, false)
+ end
+
def clone
self
end
diff --git a/src/intrinsics.cr b/src/intrinsics.cr
index edf4f14548cb..d47781a15e16 100644
--- a/src/intrinsics.cr
+++ b/src/intrinsics.cr
@@ -18,6 +18,18 @@ lib Intrinsics
fun popcount64 = "llvm.ctpop.i64"(src : Int64) : Int64
fun popcount128 = "llvm.ctpop.i128"(src : Int128) : Int128
+ fun countleading8 = "llvm.ctlz.i8"(src : Int8, zero_is_undef : Bool) : Int8
+ fun countleading16 = "llvm.ctlz.i16"(src : Int16, zero_is_undef : Bool) : Int16
+ fun countleading32 = "llvm.ctlz.i32"(src : Int32, zero_is_undef : Bool) : Int32
+ fun countleading64 = "llvm.ctlz.i64"(src : Int64, zero_is_undef : Bool) : Int64
+ fun countleading128 = "llvm.ctlz.i128"(src : Int128, zero_is_undef : Bool) : Int128
+
+ fun counttrailing8 = "llvm.cttz.i8"(src : Int8, zero_is_undef : Bool) : Int8
+ fun counttrailing16 = "llvm.cttz.i16"(src : Int16, zero_is_undef : Bool) : Int16
+ fun counttrailing32 = "llvm.cttz.i32"(src : Int32, zero_is_undef : Bool) : Int32
+ fun counttrailing64 = "llvm.cttz.i64"(src : Int64, zero_is_undef : Bool) : Int64
+ fun counttrailing128 = "llvm.cttz.i128"(src : Int128, zero_is_undef : Bool) : Int128
+
fun va_start = "llvm.va_start"(ap : Void*)
fun va_end = "llvm.va_end"(ap : Void*)
end