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[RISCV] Fix alignment when mixing rvc/norvc relax/norelax code
The issue we want to show is the alignment problem when mixing RVC and non-RVC code, especially when the RVC code is relaxed and the alignment with in the non-RVC region will not got expected alignment requirement. Give an example, this example will build with `rv64gc` and `-mrelax` option, and assume text section is start from `0x1000`: ``` _start: lui a0, %hi(foo) addi a0, a0, %lo(foo) mul a0, a1, a4 .option push .option norelax .option norvc .balign 8 SHOULD_ALIGN_8_HERE: .word 0x12345678 ``` Then when we assemble this file, assembler will insert NOP and `R_RISCV_RELAX`/`R_RISCV_ALIGN` like below: ``` Disassembly of section .text: 0000000000000000 <_start-0x2>: 0: 0001 nop 0: R_RISCV_ALIGN *ABS*+0x2 0000000000000002 <_start>: 2: 00000537 lui a0,0x0 2: R_RISCV_HI20 foo 2: R_RISCV_RELAX *ABS* 6: 00050513 mv a0,a0 6: R_RISCV_LO12_I foo 6: R_RISCV_RELAX *ABS* a: 8082 ret c: 00000013 nop 0000000000000010 <SHOULD_ALIGN_8_HERE>: 10: 12345678 .word 0x12345678 ``` And we didn't insert `R_RISCV_ALIGN` before `SHOULD_ALIGN_8_HERE`, because `norelax` option are given and the alignment seems already meet. However...the linker relaxation will remove first NOP in the text section before the `_start` symbol for meet the alignment requirement, then `SHOULD_ALIGN_8_HERE` no longer aligned to 8 bytes. So this should be fixed in the MC assembler by inserting `R_RISCV_ALIGN` correctly before `SHOULD_ALIGN_8_HERE`, even if the norelax option is given, but that not means we should always inserting that, we just need insert when relax has ever enabled on that section. Also it should emit N-2 bytes NOPs even norvc status if this section has enable RVC ever, so that linker has enough NOPs to remove for meet the alignment requirement. This is not really lld bug, but this must be put within lld testcases so that we can verify the alignment result is wrong after linking. Not all testcase are fail with out this fix, however some of them may fail on binutils side, so I think it worth to put all testcase to lld test to prevent future regression.
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‎lld/test/ELF/riscv-relax-align-1.s

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# REQUIRES: riscv
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## Testing the aligment is correct when mixing with rvc/norvc relax/norelax
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# RUN: rm -rf %t && split-file %s %t && cd %t
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## NORVC, NORELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORVC=1 --defsym=NORELAX=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORVC-NORELAX
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# NORVC-NORELAX: 0000000000001010 t SHOULD_ALIGN_8_HERE
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## NORVC, RELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORVC=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORVC
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# NORVC: 0000000000001010 t SHOULD_ALIGN_8_HERE
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## RVC, NORELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORELAX=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORELAX
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# NORELAX: 0000000000001010 t SHOULD_ALIGN_8_HERE
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## RVC, RELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=RELAX-RVC
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# RELAX-RVC: 0000000000001010 t SHOULD_ALIGN_8_HERE
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#--- a.s
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.text
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.option relax
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.balign 4
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.global _start
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.type _start, @function
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_start:
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lui a0, %hi(foo)
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addi a0, a0, %lo(foo)
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mul a0, a1, a4
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.option push
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.ifdef NORELAX
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.option norelax
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.endif
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.ifdef NORVC
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.option norvc
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.endif
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.balign 8
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SHOULD_ALIGN_8_HERE:
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.word 0x12345678
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.option pop
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foo:
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ret
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#--- lds
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ENTRY(_start)
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SECTIONS {
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.text 0x0001000 : {
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*(.text*)
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}
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}

‎lld/test/ELF/riscv-relax-align-10.s

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# REQUIRES: riscv
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## Testing the aligment is correct when mixing with rvc/norvc relax/norelax
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# RUN: rm -rf %t && split-file %s %t && cd %t
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## NORVC, NORELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORVC=1 --defsym=NORELAX=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORVC-NORELAX
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# NORVC-NORELAX: 0000000000001010 t SHOULD_ALIGN_16_HERE
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## NORVC, RELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORVC=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORVC
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# NORVC: 0000000000001010 t SHOULD_ALIGN_16_HERE
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## RVC, NORELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORELAX=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORELAX
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# NORELAX: 0000000000001010 t SHOULD_ALIGN_16_HERE
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## RVC, RELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=RELAX-RVC
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# RELAX-RVC: 0000000000001010 t SHOULD_ALIGN_16_HERE
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#--- a.s
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.text
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.option relax
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.balign 2
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.global _start
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.type _start, @function
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_start:
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call foo
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.option norvc
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mul a0, a1, a4
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.option push
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.ifdef NORELAX
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.option norelax
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.endif
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.ifdef NORVC
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.option norvc
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.endif
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.balign 16
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SHOULD_ALIGN_16_HERE:
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.word 0x12345678
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.option pop
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foo:
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ret
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#--- lds
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ENTRY(_start)
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SECTIONS {
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.text 0x0001000 : {
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*(.text*)
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}
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}

‎lld/test/ELF/riscv-relax-align-11.s

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# REQUIRES: riscv
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## Testing the aligment is correct when mixing with rvc/norvc relax/norelax
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# RUN: rm -rf %t && split-file %s %t && cd %t
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## NORVC, NORELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORVC=1 --defsym=NORELAX=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORVC-NORELAX
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# NORVC-NORELAX: 0000000000001010 t SHOULD_ALIGN_16_HERE
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## NORVC, RELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORVC=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORVC
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# NORVC: 0000000000001010 t SHOULD_ALIGN_16_HERE
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## RVC, NORELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORELAX=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORELAX
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# NORELAX: 0000000000001010 t SHOULD_ALIGN_16_HERE
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## RVC, RELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=RELAX-RVC
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# RELAX-RVC: 0000000000001010 t SHOULD_ALIGN_16_HERE
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#--- a.s
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.text
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.option relax
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.balign 2
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.global _start
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.type _start, @function
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_start:
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lui a0, %hi(foo)
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addi a0, a0, %lo(foo)
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.option norvc
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mul a0, a1, a4
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.option push
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.ifdef NORELAX
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.option norelax
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.endif
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.ifdef NORVC
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.option norvc
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.endif
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.balign 16
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SHOULD_ALIGN_16_HERE:
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ret
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.option pop
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foo:
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ret
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#--- lds
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ENTRY(_start)
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SECTIONS {
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.text 0x0001000 : {
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*(.text*)
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}
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}

‎lld/test/ELF/riscv-relax-align-12.s

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# REQUIRES: riscv
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## Testing the aligment is correct when mixing with rvc/norvc relax/norelax
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# RUN: rm -rf %t && split-file %s %t && cd %t
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## NORVC, NORELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORVC=1 --defsym=NORELAX=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORVC-NORELAX
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# NORVC-NORELAX: 0000000000001010 t SHOULD_ALIGN_16_HERE
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## NORVC, RELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORVC=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORVC
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# NORVC: 0000000000001010 t SHOULD_ALIGN_16_HERE
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## RVC, NORELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORELAX=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORELAX
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# NORELAX: 0000000000001010 t SHOULD_ALIGN_16_HERE
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## RVC, RELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=RELAX-RVC
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# RELAX-RVC: 0000000000001010 t SHOULD_ALIGN_16_HERE
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#--- a.s
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.text
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.option relax
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.balign 2
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.global _start
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.type _start, @function
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_start:
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call foo
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.option norvc
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mul a0, a1, a4
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.option push
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.ifdef NORELAX
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.option norelax
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.endif
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.ifdef NORVC
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.option norvc
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.endif
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.balign 16
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SHOULD_ALIGN_16_HERE:
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ret
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.option pop
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foo:
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ret
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#--- lds
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ENTRY(_start)
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SECTIONS {
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.text 0x0001000 : {
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*(.text*)
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}
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}

‎lld/test/ELF/riscv-relax-align-2.s

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# REQUIRES: riscv
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## Testing the aligment is correct when mixing with rvc/norvc relax/norelax
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# RUN: rm -rf %t && split-file %s %t && cd %t
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## NORVC, NORELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORVC=1 --defsym=NORELAX=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORVC-NORELAX
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# NORVC-NORELAX: 0000000000001008 t SHOULD_ALIGN_8_HERE
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## NORVC, RELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORVC=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORVC
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# NORVC: 0000000000001008 t SHOULD_ALIGN_8_HERE
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## RVC, NORELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o --defsym=NORELAX=1
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=NORELAX
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# NORELAX: 0000000000001008 t SHOULD_ALIGN_8_HERE
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## RVC, RELAX
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# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+c,+m a.s -o a.o
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# RUN: ld.lld -T lds a.o -o a.out
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# RUN: llvm-nm a.out | FileCheck %s --check-prefix=RELAX-RVC
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# RELAX-RVC: 0000000000001008 t SHOULD_ALIGN_8_HERE
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#--- a.s
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.text
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.option relax
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.balign 4
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.global _start
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.type _start, @function
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_start:
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call foo
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mul a0, a1, a4
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.option push
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.ifdef NORELAX
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.option norelax
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.endif
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.ifdef NORVC
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.option norvc
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.endif
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.balign 8
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SHOULD_ALIGN_8_HERE:
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.word 0x12345678
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.option pop
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foo:
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ret
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#--- lds
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ENTRY(_start)
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SECTIONS {
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.text 0x0001000 : {
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*(.text*)
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}
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}

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