[llvm-dev] Strange Machineinstr

[Muhui Jiang via llvm-dev]

Hi

I write a machinefunction pass  to print all the machinefunction's machine
instructions.

My target architecture is ARM. However, I don't understand some part of the
machine instructions.

Below is some of the assembly language for function A.

.text:0001C034                 STMFD   SP!, {R4,R10,R11,LR}
> .text:0001C038                 ADD     R11, SP, #8
> .text:0001C03C                 SUB     SP, SP, #0x20
> .text:0001C040                 STR     R0, [R11,#statbuf]
> .text:0001C044                 STR     R1, [SP,#0x28+var_14]
> .text:0001C048                 LDR     R0, [SP,#0x28+var_14]
> .text:0001C04C                 LDR     R0, [R0]
> .text:0001C050                 STR     R0, [SP,#0x28+ts]
> .text:0001C054                 LDR     R0, [SP,#0x28+ts]
> .text:0001C058                 LDR     R0, [R0,#4]
> .text:0001C05C                 CMN     R0, #0xC0000002
> .text:0001C060                 BNE     loc_1C088
> .text:0001C064                 B       loc_1C068
>
>
Below is the corresponding MachineInstr

%1:gpr = COPY $r1
>
> %0:gpr = COPY $r0
>
> %3:gpr = COPY %1:gpr
>
> %2:gpr = COPY %0:gpr
>
> STRi12 %0:gpr, %stack.1.statbuf.addr, 0, 14, $noreg :: (store 4 into
>> %ir.statbuf.addr)
>
> STRi12 %1:gpr, %stack.2.ts.addr, 0, 14, $noreg :: (store 4 into
>> %ir.ts.addr)
>
> %4:gpr = LDRi12 %stack.2.ts.addr, 0, 14, $noreg
>
> %5:gpr = LDRi12 killed %4:gpr, 0, 14, $noreg
>
> STRi12 killed %5:gpr, %stack.3.timespec, 0, 14, $noreg
>
> %6:gpr = LDRi12 %stack.3.timespec, 0, 14, $noreg
>
> %7:gpr = LDRi12 killed %6:gpr, 4, 14, $noreg
>
> CMNri killed %7:gpr, -1073741822, 14, $noreg
>
> Bcc %bb.3, 1, $cpsr
>
> B %bb.1
>
>
I don't know how "STMFD   SP!, {R4,R10,R11,LR}" is translated into the
machineinstr. Also, what does $noreg mean? what does gpr and the value in
front of it mean? It would be great if someone who are familiar with this
can explain it to me or give me some reference. Thank you very much.

Regards
Muhui
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