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Keil -O0 and -O1 optimize

Mr.Anderson

My code

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while(usart_transmit_status);
usart_transmit_status = 1;
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

translate at -O0

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0x08001EB4 4807 LDR r0,[pc,#28] ; @0x08001ED4
0x08001EB6 7800 LDRB r0,[r0,#0x00]
0x08001EB8 2800 CMP r0,#0x00
0x08001EBA D1FB BNE 0x08001EB4
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

and translate at -O1

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0x08001A6E 4907 LDR r1,[pc,#28] ; @0x08001A8C
0x08001A70 7808 LDRB r0,[r1,#0x00]
0x08001A72 2800 CMP r0,#0x00
0x08001A74 D1FD BNE 0x08001A72
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

It leads to an error because R0 changes in interruption

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