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Inline Assembler

Some Assembly Required

D, being a systems programming language, provides an inline assembler. The inline assembler is standardized for D implementations across the same CPU family, for example, the Intel Pentium inline assembler for a Win32 D compiler will be syntax compatible with the inline assembler for Linux running on an Intel Pentium.

Implementations of D on different architectures, however, are free to innovate upon the memory model, function call/return conventions, argument passing conventions, etc.

This document describes the x86 and x86_64 implementations of the inline assembler. The inline assembler platform support that a compiler provides is indicated by the D_InlineAsm_X86 and D_InlineAsm_X86_64 version identifiers, respectively.

    Identifier : AsmInstruction
    align IntegerExpression
    db Operands
    ds Operands
    di Operands
    dl Operands
    df Operands
    dd Operands
    de Operands
    db StringLiteral
    ds StringLiteral
    di StringLiteral
    dl StringLiteral
    dw StringLiteral
    dq StringLiteral
    Opcode Operands
Operands: Operand Operand , Operands


Assembler instructions can be labeled just like other statements. They can be the target of goto statements. For example:

void *pc;
    call L1          ;
  L1:                ;
    pop  EBX         ;
    mov  pc[EBP],EBX ; // pc now points to code at L1

align IntegerExpression


Causes the assembler to emit NOP instructions to align the next assembler instruction on an IntegerExpression boundary. IntegerExpression must evaluate at compile time to an integer that is a power of 2.

Aligning the start of a loop body can sometimes have a dramatic effect on the execution speed.


Causes the assembler to emit NOP instructions to align the next assembler instruction on an even boundary.


Causes the compiler to not generate the function prolog and epilog sequences. This means such is the responsibility of inline assembly programmer, and is normally used when the entire function is to be written in assembler.

db, ds, di, dl, df, dd, de

These pseudo ops are for inserting raw data directly into the code. db is for bytes, ds is for 16 bit words, di is for 32 bit words, dl is for 64 bit words, df is for 32 bit floats, dd is for 64 bit doubles, and de is for 80 bit extended reals. Each can have multiple operands. If an operand is a string literal, it is as if there were length operands, where length is the number of characters in the string. One character is used per operand. For example:

    db 5,6,0x83;   // insert bytes 0x05, 0x06, and 0x83 into code
    ds 0x1234;     // insert bytes 0x34, 0x12
    di 0x1234;     // insert bytes 0x34, 0x12, 0x00, 0x00
    dl 0x1234;     // insert bytes 0x34, 0x12, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
    df 1.234;      // insert float 1.234
    dd 1.234;      // insert double 1.234
    de 1.234;      // insert real 1.234
    db "abc";      // insert bytes 0x61, 0x62, and 0x63
    ds "abc";      // insert bytes 0x61, 0x00, 0x62, 0x00, 0x63, 0x00


A list of supported opcodes is at the end.

The following registers are supported. Register names are always in upper case.

    BP EBP
    SP ESP
    DI EDI
    SI ESI
    CR0 CR2 CR3 CR4
    DR0 DR1 DR2 DR3 DR6 DR7
    TR3 TR4 TR5 TR6 TR7
    ST(0) ST(1) ST(2) ST(3) ST(4) ST(5) ST(6) ST(7)
    MM0  MM1  MM2  MM3  MM4  MM5  MM6  MM7

x86_64 adds these additional registers.

    BPL  RBP
    SPL  RSP
    DIL  RDI
    SIL  RSI
    R8B  R8W  R8D  R8
    R9B  R9W  R9D  R9
    R10B R10W R10D R10
    R11B R11W R11D R11
    R12B R12W R12D R12
    R13B R13W R13D R13
    R14B R14W R14D R14
    R15B R15W R15D R15
    XMM8 XMM9 XMM10 XMM11 XMM12 XMM13 XMM14 XMM15
    YMM0 YMM1 YMM2  YMM3  YMM4  YMM5  YMM6  YMM7
    YMM8 YMM9 YMM10 YMM11 YMM12 YMM13 YMM14 YMM15

Special Cases

lock, rep, repe, repne, repnz, repz
These prefix instructions do not appear in the same statement as the instructions they prefix; they appear in their own statement. For example:
    rep   ;
    movsb ;
This opcode is not supported by the assembler, instead use
    rep  ;
    nop  ;
which produces the same result.
floating point ops
Use the two operand form of the instruction format;
fdiv ST(1);     // wrong
fmul ST;        // wrong
fdiv ST,ST(1);  // right
fmul ST,ST(0);  // right


AsmExp: AsmLogOrExp AsmLogOrExp ? AsmExp : AsmExp
AsmLogOrExp: AsmLogAndExp AsmLogOrExp || AsmLogAndExp
AsmLogAndExp: AsmOrExp AsmLogAndExp && AsmOrExp
AsmOrExp: AsmXorExp AsmOrExp | AsmXorExp
AsmXorExp: AsmAndExp AsmXorExp ^ AsmAndExp
AsmAndExp: AsmEqualExp AsmAndExp & AsmEqualExp
AsmEqualExp: AsmRelExp AsmEqualExp == AsmRelExp AsmEqualExp != AsmRelExp
AsmRelExp: AsmShiftExp AsmRelExp < AsmShiftExp AsmRelExp <= AsmShiftExp AsmRelExp > AsmShiftExp AsmRelExp >= AsmShiftExp
AsmShiftExp: AsmAddExp AsmShiftExp << AsmAddExp AsmShiftExp >> AsmAddExp AsmShiftExp >>> AsmAddExp
AsmAddExp: AsmMulExp AsmAddExp + AsmMulExp AsmAddExp - AsmMulExp
AsmMulExp: AsmBrExp AsmMulExp * AsmBrExp AsmMulExp / AsmBrExp AsmMulExp % AsmBrExp
AsmBrExp: AsmUnaExp AsmBrExp [ AsmExp ]
AsmUnaExp: AsmTypePrefix AsmExp offsetof AsmExp seg AsmExp + AsmUnaExp - AsmUnaExp ! AsmUnaExp ~ AsmUnaExp AsmPrimaryExp
AsmPrimaryExp: IntegerLiteral FloatLiteral __LOCAL_SIZE $ Register Register : AsmExp Register64 Register64 : AsmExp DotIdentifier this
DotIdentifier: Identifier Identifier . DotIdentifier

The operand syntax more or less follows the Intel CPU documentation conventions. In particular, the convention is that for two operand instructions the source is the right operand and the destination is the left operand. The syntax differs from that of Intel's in order to be compatible with the D language tokenizer and to simplify parsing.

The seg means load the segment number that the symbol is in. This is not relevant for flat model code. Instead, do a move from the relevant segment register.

Operand Types

    near ptr
    far ptr
    byte ptr
    short ptr
    int ptr
    word ptr
    dword ptr
    qword ptr
    float ptr
    double ptr
    real ptr

In cases where the operand size is ambiguous, as in:

add [EAX],3     ;
it can be disambiguated by using an AsmTypePrefix:
add  byte ptr [EAX],3 ;
add  int ptr [EAX],7  ;

far ptr is not relevant for flat model code.

Struct/Union/Class Member Offsets

To access members of an aggregate, given a pointer to the aggregate is in a register, use the .offsetof property of the qualified name of the member:

struct Foo { int a,b,c; }
int bar(Foo *f)
        mov EBX,f                   ;
        mov EAX,Foo.b.offsetof[EBX] ;
void main()
    Foo f = Foo(0, 2, 0);
    assert(bar(&f) == 2);

Alternatively, inside the scope of an aggregate, only the member name is needed:

struct Foo   // or class
    int a,b,c;
    int bar()
            mov EBX, this   ;
            mov EAX, b[EBX] ;
void main()
    Foo f = Foo(0, 2, 0);
    assert( == 2);

Stack Variables

Stack variables (variables local to a function and allocated on the stack) are accessed via the name of the variable indexed by EBP:

int foo(int x)
        mov EAX,x[EBP] ; // loads value of parameter x into EAX
        mov EAX,x      ; // does the same thing

If the [EBP] is omitted, it is assumed for local variables. If naked is used, this no longer holds.

Special Symbols

Represents the program counter of the start of the next instruction. So,
jmp  $  ;
branches to the instruction following the jmp instruction. The $ can only appear as the target of a jmp or call instruction.
This gets replaced by the number of local bytes in the local stack frame. It is most handy when the naked is invoked and a custom stack frame is programmed.

Opcodes Supported

aaa aad aam aas adc
add addpd addps addsd addss
and andnpd andnps andpd andps
arpl bound bsf bsr bswap
bt btc btr bts call
cbw cdq clc cld clflush
cli clts cmc cmova cmovae
cmovb cmovbe cmovc cmove cmovg
cmovge cmovl cmovle cmovna cmovnae
cmovnb cmovnbe cmovnc cmovne cmovng
cmovnge cmovnl cmovnle cmovno cmovnp
cmovns cmovnz cmovo cmovp cmovpe
cmovpo cmovs cmovz cmp cmppd
cmpps cmps cmpsb cmpsd cmpss
cmpsw cmpxchg cmpxchg8b cmpxchg16b
comisd comiss
cpuid cvtdq2pd cvtdq2ps cvtpd2dq cvtpd2pi
cvtpd2ps cvtpi2pd cvtpi2ps cvtps2dq cvtps2pd
cvtps2pi cvtsd2si cvtsd2ss cvtsi2sd cvtsi2ss
cvtss2sd cvtss2si cvttpd2dq cvttpd2pi cvttps2dq
cvttps2pi cvttsd2si cvttss2si cwd cwde
da daa das db dd
de dec df di div
divpd divps divsd divss dl
dq ds dt dw emms
enter f2xm1 fabs fadd faddp
fbld fbstp fchs fclex fcmovb
fcmovbe fcmove fcmovnb fcmovnbe fcmovne
fcmovnu fcmovu fcom fcomi fcomip
fcomp fcompp fcos fdecstp fdisi
fdiv fdivp fdivr fdivrp feni
ffree fiadd ficom ficomp fidiv
fidivr fild fimul fincstp finit
fist fistp fisub fisubr fld
fld1 fldcw fldenv fldl2e fldl2t
fldlg2 fldln2 fldpi fldz fmul
fmulp fnclex fndisi fneni fninit
fnop fnsave fnstcw fnstenv fnstsw
fpatan fprem fprem1 fptan frndint
frstor fsave fscale fsetpm fsin
fsincos fsqrt fst fstcw fstenv
fstp fstsw fsub fsubp fsubr
fsubrp ftst fucom fucomi fucomip
fucomp fucompp fwait fxam fxch
fxrstor fxsave fxtract fyl2x fyl2xp1
hlt idiv imul in inc
ins insb insd insw int
into invd invlpg iret iretd
ja jae jb jbe jc
jcxz je jecxz jg jge
jl jle jmp jna jnae
jnb jnbe jnc jne jng
jnge jnl jnle jno jnp
jns jnz jo jp jpe
jpo js jz lahf lar
ldmxcsr lds lea leave les
lfence lfs lgdt lgs lidt
lldt lmsw lock lods lodsb
lodsd lodsw loop loope loopne
loopnz loopz lsl lss ltr
maskmovdqu maskmovq maxpd maxps maxsd
maxss mfence minpd minps minsd
minss mov movapd movaps movd
movdq2q movdqa movdqu movhlps movhpd
movhps movlhps movlpd movlps movmskpd
movmskps movntdq movnti movntpd movntps
movntq movq movq2dq movs movsb
movsd movss movsw movsx movupd
movups movzx mul mulpd mulps
mulsd mulss neg nop not
or orpd orps out outs
outsb outsd outsw packssdw packsswb
packuswb paddb paddd paddq paddsb
paddsw paddusb paddusw paddw pand
pandn pavgb pavgw pcmpeqb pcmpeqd
pcmpeqw pcmpgtb pcmpgtd pcmpgtw pextrw
pinsrw pmaddwd pmaxsw pmaxub pminsw
pminub pmovmskb pmulhuw pmulhw pmullw
pmuludq pop popa popad popf
popfd por prefetchnta prefetcht0 prefetcht1
prefetcht2 psadbw pshufd pshufhw pshuflw
pshufw pslld pslldq psllq psllw
psrad psraw psrld psrldq psrlq
psrlw psubb psubd psubq psubsb
psubsw psubusb psubusw psubw punpckhbw
punpckhdq punpckhqdq punpckhwd punpcklbw punpckldq
punpcklqdq punpcklwd push pusha pushad
pushf pushfd pxor rcl rcpps
rcpss rcr rdmsr rdpmc rdtsc
rep repe repne repnz repz
ret retf rol ror rsm
rsqrtps rsqrtss sahf sal sar
sbb scas scasb scasd scasw
seta setae setb setbe setc
sete setg setge setl setle
setna setnae setnb setnbe setnc
setne setng setnge setnl setnle
setno setnp setns setnz seto
setp setpe setpo sets setz
sfence sgdt shl shld shr
shrd shufpd shufps sidt sldt
smsw sqrtpd sqrtps sqrtsd sqrtss
stc std sti stmxcsr stos
stosb stosd stosw str sub
subpd subps subsd subss syscall
sysenter sysexit sysret test ucomisd
ucomiss ud2 unpckhpd unpckhps unpcklpd
unpcklps verr verw wait wbinvd
wrmsr xadd xchg xlat xlatb
xor xorpd xorps

Pentium 4 (Prescott) Opcodes Supported

Pentium 4 Opcodes
addsubpd addsubps fisttp haddpd haddps
hsubpd hsubps lddqu monitor movddup
movshdup movsldup mwait

AMD Opcodes Supported

AMD Opcodes
pavgusb pf2id pfacc pfadd pfcmpeq
pfcmpge pfcmpgt pfmax pfmin pfmul
pfnacc pfpnacc pfrcp pfrcpit1 pfrcpit2
pfrsqit1 pfrsqrt pfsub pfsubr pi2fd
pmulhrw pswapd


SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2 and AVX are supported.

Floating Point
Embedded Documentation