什么时候修改CPSR GE[3:0]位
When will CPSR GE[3:0] bits be modified
我在 ARM 文档中读到：
GE[3:0], bits[19:16]
The instructions described in Parallel addition and subtraction instructions on
page A4-171 update these flags to indicate the results from individual bytes or halfwords
of the operation. These flags can control a later SEL instruction.
那么显然 GE[3:0] 代表 "eq/lt/gt"？
我遇到了几个奇怪的问题，我还没有任何线索，但它们都有 CPSR 值 xxxf0030，所以 GE 位是 0b1111？那代表什么？这些GE位正常吗？
提前致谢！
在 ARMv7 ARM（匹配该文本）中，如何设置 GE 标志的详细信息仅在并行指令本身的操作伪代码中。可悲的是，他们似乎已经删除了 ARMv6 ARM 中的这个很好的散文描述：
Instructions that operate on halfwords:
- set or clear GE[3:2] together, based on the result of the top halfword calculation
- set or clear GE[1:0] together, based on the result of the bottom halfword calculation.
Instructions that operate on bytes:
- set or clear GE[3] according to the result of the top byte calculation
- set or clear GE[2] according to the result of the second byte calculation
- set or clear GE[1] according to the result of the third byte calculation
- set or clear GE[0] according to the result of the bottom byte calculation.
Each bit is set (otherwise cleared) if the results of the
corresponding calculation are as follows:
- for unsigned byte addition, if the result is greater than or equal to 2^8
- for unsigned halfword addition, if the result is greater than or equal to 2^16
- for unsigned subtraction, if the result is greater than or equal to zero
- for signed arithmetic, if the result is greater than or equal to zero.
作为算术标志，它们可以有任何旧值（重置时未定义，可以通过 APSR 自由写入），所以除非你专门使用其中一条设置它们的指令，否则它们几乎是无意义，可以忽略。
我在 ARM 文档中读到：
GE[3:0], bits[19:16] The instructions described in Parallel addition and subtraction instructions on page A4-171 update these flags to indicate the results from individual bytes or halfwords of the operation. These flags can control a later SEL instruction.
那么显然 GE[3:0] 代表 "eq/lt/gt"？
我遇到了几个奇怪的问题，我还没有任何线索，但它们都有 CPSR 值 xxxf0030，所以 GE 位是 0b1111？那代表什么？这些GE位正常吗？
提前致谢！
在 ARMv7 ARM（匹配该文本）中，如何设置 GE 标志的详细信息仅在并行指令本身的操作伪代码中。可悲的是，他们似乎已经删除了 ARMv6 ARM 中的这个很好的散文描述：
Instructions that operate on halfwords:
- set or clear GE[3:2] together, based on the result of the top halfword calculation
- set or clear GE[1:0] together, based on the result of the bottom halfword calculation.
Instructions that operate on bytes:
- set or clear GE[3] according to the result of the top byte calculation
- set or clear GE[2] according to the result of the second byte calculation
- set or clear GE[1] according to the result of the third byte calculation
- set or clear GE[0] according to the result of the bottom byte calculation.
Each bit is set (otherwise cleared) if the results of the corresponding calculation are as follows:
- for unsigned byte addition, if the result is greater than or equal to 2^8
- for unsigned halfword addition, if the result is greater than or equal to 2^16
- for unsigned subtraction, if the result is greater than or equal to zero
- for signed arithmetic, if the result is greater than or equal to zero.
作为算术标志，它们可以有任何旧值（重置时未定义，可以通过 APSR 自由写入），所以除非你专门使用其中一条设置它们的指令，否则它们几乎是无意义，可以忽略。