Use the following directives with ml64.exe:

• .ALLOCSTACK

• .ENDPROLOG

• .PUSHFRAME

• .PUSHREG

• .SAVEREG

• .SAVEXMM128

• .SETFRAME

In addition, the PROC directive was updated for use with ml64.exe.

MASM will emit the 0x67 address size override if a memory operand includes 32-bit registers. For example, the following examples cause the address size override to be emitted:

mov rax, QWORD PTR [ecx]
mov eax, DWORD PTR [ecx*2+r10d]
mov eax, DWORD PTR [ecx*2+r10d+0100h]
prefetch [eax]
movnti rax, QWORD PTR [r8d]

MASM assumes that if a 32-bit displacement appears alone as a memory operand, 64-bit addressing is intended. There is currently no support for 32-bit addressing with such operands.

Finally, mixing register sizes within a memory operand, as demonstrated in the following code, will generate an error.

mov eax, DWORD PTR [rcx*2+r10d]
mov eax, DWORD PTR [ecx*2+r10+0100h]

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