我可以将 64 位常量添加到 64 位寄存器吗? [英] Can I add 64bit constants to 64bit registers?

问题描述

在我的 64 位英特尔机器上，以下代码有效:

At my 64bit Intel machine following code works:

mov rdi, 1 << 40
add r10, rdi

而这个看起来相当类似的会产生警告并且不起作用:

and this quite equivalent looking one produces a warning and doesn't work:

add r10, 1 << 40

我应该坚持第一还是我错过了什么?这种行为似乎很尴尬.

Should I just stick with number 1 or am I missing something? This behaviour seems akward.

代码 nr 2 产生的警告:

The warning produced by code nr 2:

warning: signed dword immediate exceeds bounds

推荐答案

mov r/m64, imm64 有操作码，但 add r/m64 没有操作码，imm64 在 x86-64 指令集中.换句话说:您不能对 add 使用 64 位立即数操作数，但可以为 mov 使用(有许多指令没有 imm64 变体；您可以查看英特尔软件开发人员手册中的指令集参考，以检查哪些指令具有此类变体，哪些没有).

There is an opcode for mov r/m64, imm64, but there is no opcode for add r/m64, imm64 in the x86-64 instruction set. In other words: you cannot use 64-bit immediate operand for add, but you can for mov (there are many instructions that don't have the imm64 variant; you can check the Instruction Set Reference in the Intel Software Developer Manual to check which instructions have such variant and which don't).

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