Use BSR instruction to implement fixnum-log2 intrinsic

basis/compiler/cfg/hats/hats.factor

@@ -39,6 +39,7 @@ IN: compiler.cfg.hats
 : ^^shr-imm ( src1 src2 -- dst ) ^^i2 ##shr-imm ; inline
 : ^^sar-imm ( src1 src2 -- dst ) ^^i2 ##sar-imm ; inline
 : ^^not ( src -- dst ) ^^i1 ##not ; inline
+: ^^log2 ( src -- dst ) ^^i1 ##log2 ; inline
 : ^^bignum>integer ( src -- dst ) ^^i1 i ##bignum>integer ; inline
 : ^^integer>bignum ( src -- dst ) ^^i1 i ##integer>bignum ; inline
 : ^^add-float ( src1 src2 -- dst ) ^^d2 ##add-float ; inline

basis/compiler/cfg/instructions/instructions.factor

@@ -92,6 +92,7 @@ INSN: ##shl-imm < ##binary-imm ;
 INSN: ##shr-imm < ##binary-imm ;
 INSN: ##sar-imm < ##binary-imm ;
 INSN: ##not < ##unary ;
+INSN: ##log2 < ##unary ;
 
 ! Overflowing arithmetic
 TUPLE: ##fixnum-overflow < insn src1 src2 ;

basis/compiler/cfg/intrinsics/fixnum/fixnum.factor

@@ -53,6 +53,9 @@ IN: compiler.cfg.intrinsics.fixnum
 : emit-fixnum-bitnot ( -- )
     ds-pop ^^not tag-mask get ^^xor-imm ds-push ;
 
+: emit-fixnum-log2 ( -- )
+    ds-pop ^^log2 tag-bits get ^^sub-imm ^^tag-fixnum ds-push ;
+
 : (emit-fixnum*fast) ( -- dst )
     2inputs ^^untag-fixnum ^^mul ;
 

basis/compiler/cfg/intrinsics/intrinsics.factor

@@ -19,6 +19,7 @@ QUALIFIED: slots.private
 QUALIFIED: strings.private
 QUALIFIED: classes.tuple.private
 QUALIFIED: math.private
+QUALIFIED: math.integers.private
 QUALIFIED: alien.accessors
 IN: compiler.cfg.intrinsics
 
@@ -93,6 +94,9 @@ IN: compiler.cfg.intrinsics
         alien.accessors:set-alien-double
     } [ t "intrinsic" set-word-prop ] each ;
 
+: enable-fixnum-log2 ( -- )
+    \ math.integers.private:fixnum-log2 t "intrinsic" set-word-prop ;
+
 : emit-intrinsic ( node word -- node/f )
     {
         { \ kernel.private:tag [ drop emit-tag iterate-next ] }
@@ -108,6 +112,7 @@ IN: compiler.cfg.intrinsics
         { \ math.private:fixnum-bitxor [ [ ^^xor ] [ ^^xor-imm ] emit-fixnum-op iterate-next ] }
         { \ math.private:fixnum-shift-fast [ emit-fixnum-shift-fast iterate-next ] }
         { \ math.private:fixnum-bitnot [ drop emit-fixnum-bitnot iterate-next ] }
+        { \ math.integers.private:fixnum-log2 [ drop emit-fixnum-log2 iterate-next ] }
         { \ math.private:fixnum*fast [ emit-fixnum*fast iterate-next ] }
         { \ math.private:fixnum< [ cc< emit-fixnum-comparison iterate-next ] }
         { \ math.private:fixnum<= [ cc<= emit-fixnum-comparison iterate-next ] }

basis/compiler/codegen/codegen.factor

@@ -163,6 +163,7 @@ M: ##shl-imm generate-insn dst/src1/src2 %shl-imm ;
 M: ##shr-imm generate-insn dst/src1/src2 %shr-imm ;
 M: ##sar-imm generate-insn dst/src1/src2 %sar-imm ;
 M: ##not     generate-insn dst/src       %not     ;
+M: ##log2    generate-insn dst/src       %log2    ;
 
 : src1/src2 ( insn -- src1 src2 )
     [ src1>> register ] [ src2>> register ] bi ; inline

basis/cpu/architecture/architecture.factor

@@ -77,6 +77,7 @@ HOOK: %shl-imm cpu ( dst src1 src2 -- )
 HOOK: %shr-imm cpu ( dst src1 src2 -- )
 HOOK: %sar-imm cpu ( dst src1 src2 -- )
 HOOK: %not     cpu ( dst src -- )
+HOOK: %log2    cpu ( dst src -- )
 
 HOOK: %fixnum-add cpu ( src1 src2 -- )
 HOOK: %fixnum-add-tail cpu ( src1 src2 -- )

basis/cpu/x86/assembler/assembler.factor

@@ -384,6 +384,8 @@ M: operand CMP OCT: 070 2-operand ;
 
 : XCHG ( dst src -- ) OCT: 207 2-operand ;
 
+: BSR ( dst src -- ) swap { HEX: 0f HEX: bd } (2-operand) ;
+
 : NOT  ( dst -- ) { BIN: 010 t HEX: f7 } 1-operand ;
 : NEG  ( dst -- ) { BIN: 011 t HEX: f7 } 1-operand ;
 : MUL  ( dst -- ) { BIN: 100 t HEX: f7 } 1-operand ;

basis/cpu/x86/x86.factor

@@ -5,10 +5,12 @@ cpu.x86.assembler cpu.x86.assembler.private cpu.architecture
 kernel kernel.private math memory namespaces make sequences
 words system layouts combinators math.order fry locals
 compiler.constants compiler.cfg.registers
-compiler.cfg.instructions compiler.codegen
-compiler.codegen.fixup ;
+compiler.cfg.instructions compiler.cfg.intrinsics
+compiler.codegen compiler.codegen.fixup ;
 IN: cpu.x86
 
+<< enable-fixnum-log2 >>
+
 M: x86 two-operand? t ;
 
 HOOK: temp-reg-1 cpu ( -- reg )
@@ -92,6 +94,7 @@ M: x86 %shl-imm nip SHL ;
 M: x86 %shr-imm nip SHR ;
 M: x86 %sar-imm nip SAR ;
 M: x86 %not     drop NOT ;
+M: x86 %log2    BSR ;
 
 : ?MOV ( dst src -- )
     2dup = [ 2drop ] [ MOV ] if ; inline

core/math/integers/integers.factor

@@ -40,11 +40,13 @@ M: fixnum bitnot fixnum-bitnot ;
 
 M: fixnum bit? neg shift 1 bitand 0 > ;
 
-: (fixnum-log2) ( accum n -- accum )
-    dup 1 number= [ drop ] [ [ 1+ ] [ 2/ ] bi* (fixnum-log2) ] if ;
-    inline recursive
+: fixnum-log2 ( x -- n )
+    0 swap [ dup 1 number= not ] [ [ 1+ ] [ 2/ ] bi* ] [ ] while drop ;
 
-M: fixnum (log2) 0 swap (fixnum-log2) ;
+M: fixnum (log2) fixnum-log2 ;
+
+M: integer next-power-of-2
+    dup 2 <= [ drop 2 ] [ 1- log2 1+ 2^ ] if ;
 
 M: bignum >fixnum bignum>fixnum ;
 M: bignum >bignum ;

core/math/math.factor

@@ -53,7 +53,7 @@ PRIVATE>
         "log2 expects positive inputs" throw
     ] [
         (log2)
-    ] if ; foldable
+    ] if ; inline
 
 : zero? ( x -- ? ) 0 number= ; inline
 : 1+ ( x -- y ) 1 + ; inline
@@ -103,14 +103,9 @@ M: float fp-infinity? ( float -- ? )
         drop f
     ] if ;
 
-: (next-power-of-2) ( i n -- n )
-    2dup >= [
-        drop
-    ] [
-        [ 1 shift ] dip (next-power-of-2)
-    ] if ;
+GENERIC: next-power-of-2 ( m -- n ) foldable
 
-: next-power-of-2 ( m -- n ) 2 swap (next-power-of-2) ; foldable
+M: real next-power-of-2 1+ >integer next-power-of-2 ;
 
 : power-of-2? ( n -- ? )
     dup 0 <= [ drop f ] [ dup 1- bitand zero? ] if ; foldable