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cpu.x86.assembler: MOV zero extension for small immediates (#1593) 

Instructions eg: mov rax, 123 can be equivalent mov eax, 123 which are
shorter.
locals-and-roots
Björn Lindqvist 2016-05-19 23:02:48 +02:00
parent 0fc8fb22ca
commit 4230d2502a
3 changed files with 28 additions and 13 deletions
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16
basis/cpu/x86/assembler/assembler-docs.factor
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@ -1,5 +1,5 @@
USING: compiler.codegen.labels cpu.x86.assembler.private help.markup
help.syntax sequences ;
help.syntax kernel math sequences ;
IN: cpu.x86.assembler
HELP: 1-operand
@ -30,9 +30,17 @@ HELP: MOV
{ $description "Moves a value from one place to another." } ;
HELP: (MOV-I)
{ $values { "dst" "destination" "src" "immediate value" } }
{ $description "MOV where the src is immediate." } ;
{ $values { "dst" "destination" } { "src" "immediate value" } }
{ $description "MOV where 'src' is immediate. If dst is a 64-bit register and the 'src' value fits in 32 bits, then zero extension is taken advantage of by downgrading 'dst' to a 32-bit register. That way, the instruction gets a shorter encoding." } ;
ARTICLE: "cpu.x86.assembler" "X86 assembler" "This vocab implements an assembler for x86 architectures." ;
HELP: zero-extendable?
{ $values { "imm" integer } { "?" boolean } }
{ $description "All positive 32-bit numbers are zero extendable except for 0 which is the value used for relocations." } ;
ARTICLE: "cpu.x86.assembler" "X86 assembler"
"This vocab implements an assembler for x86 architectures."
$nl
"Instructions:"
{ $subsections MOV } ;
ABOUT: "cpu.x86.assembler"

7
basis/cpu/x86/assembler/assembler-tests.factor
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@ -12,11 +12,8 @@ IN: cpu.x86.assembler.tests
{ { 136 235 } } [ [ BL CH MOV ] { } make ] unit-test
! immediate operands
cell 4 = [
[ { 0xb9 0x01 0x00 0x00 0x00 } ] [ [ ECX 1 MOV ] { } make ] unit-test
] [
[ { 0xb9 0x01 0x00 0x00 0x00 0x00 0x00 0x00 0x00 } ] [ [ ECX 1 MOV ] { } make ] unit-test
] if
[ { 0xb9 0x01 0x00 0x00 0x00 } ] [ [ ECX 1 MOV ] { } make ] unit-test
[ { 0xb9 0x01 0x00 0x00 0x00 } ] [ [ RCX 1 MOV ] { } make ] unit-test
{ { 0x83 0xc1 0x01 } } [ [ ECX 1 ADD ] { } make ] unit-test
{ { 0x81 0xc1 0x96 0x00 0x00 0x00 } } [ [ ECX 150 ADD ] { } make ] unit-test

18
basis/cpu/x86/assembler/assembler.factor
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@ -212,13 +212,23 @@ M: operand POP { 0b000 f 0x8f } 1-operand ;
<PRIVATE
: zero-extendable? ( imm -- ? )
1 32 2^ 1 - between? ;
GENERIC# (MOV-I) 1 ( dst src -- )
M: register (MOV-I)
dup byte?
[ [ t 0xb0 short-operand ] [ 1, ] bi* ]
[ [ t 0xb8 short-operand ] [ cell, ] bi* ]
if ;
{
{
[ dup byte? ]
[ [ t 0xb0 short-operand ] [ 1, ] bi* ]
}
{
[ dup zero-extendable? ]
[ [ 32-bit-version-of t 0xb8 short-operand ] [ 4, ] bi* ]
}
[ [ t 0xb8 short-operand ] [ cell, ] bi* ]
} cond ;
M: operand (MOV-I)
{ 0b000 t 0xc6 }