1、globe pointer($gp) define
1.1、It is the address in the middle of data sections.
1.2、Linker places scalar data around it so that they can be accessed efficiently by $gp-based load/store instructions and their addresses can be calculated efficiently by $gp-based add instructions.
2、$gp relative instruction
2.1、swi.gp Rt,[+(imm17s<<2)]
Rt = [imm17s<<2]
The (imm17s << 2) value covers a range of 512K byte region relative to the location pointed to by the GP register.
2.2、ADDI.gp Rt, imm19s
Rt = R29 + SE(imm19s)
The imm19s value covers a range of 512K byte region relative to the location pointed to by the GP register.
3、$gp example at assembly
3.1、Relax optimization
3.1.1、Default is on.
3.1.2、Trun off relax linker option : -mno-relax.
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ex:
example code
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Relax function
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No relax function
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