I have a question on the GCC optimization. I am using
GCC3.0.4 MIPS crosscompiler on Redhat 7.1. In a
function I did the following:
register unsigned int temp;
temp = devict.dev1.devtc
I compiled the code with optimization level 0 and
found something weird about the register variable
temp. This is shows in the disassembly file:
for temp = devict.dev1.devtc
lui $3, 0xb801
lw $3, 28($3)
This is right since the CPU loads the
devict.dev1.devtc value from memory to the register 3.
However, after the above instructions, I found:
sw $3, 0($30)
lw $2, 0($30)
now the compiler asked the CPU to store the register
in the stack. However, I declared the variable as a
register, how come it still needs to go to the stack?
I compiled the same code with gcc-2.8.1, optimization
level 0, and did not find the same issue there.
Why the gcc-3.0.4 did the weird stuff? Do I have to
use at least level 1 to make the register declared
work for it?
Thanks a lot!
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