<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/107520>107520</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [RISC-V] Outliner can place paired %pcrel_hi/%pcrel_lo in different sections resulting in link errors for GNU ld
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            backend:RISC-V
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
            jonathonpenix
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          jonathonpenix
      </td>
    </tr>
</table>

<pre>
    Please see below for a small-ish reproducer to demonstrate the issue. I am testing with LLVM built at ede40da1f8c1e91601b985cd32ad785aa8806880 and GNU ld from binutils v2.39.

```
$ cat test.c
#include <stdio.h>
#include <stdlib.h>

int v1 = 0;
int v2 = 1;

int *a1;
int *a2;

int main(int argc, char **argv)
{
  a1 = malloc(sizeof(int) * 2);
  a2 = malloc(sizeof(int) * 2);
  fprintf(stderr, "%d\n", 0);
  for (int i = 0; i <= 1; i++) {
    printf("%d %d\n", a1[v1], a2[v1]);
    printf("%d %d\n", a1[v2], a2[v2]);
  }
}
$ clang --target=riscv32-linux-gnu -mabi=ilp32 --sysroot=/path/to/riscv/sysroot --gcc-toolchain=/path/to/gcc/toolchain test.c -Oz
/tmp/test-5a64de.o: in function `OUTLINED_FUNCTION_0':
test.c:(.text+0x4): dangerous relocation: %pcrel_lo missing matching %pcrel_hi
clang: error: linker command failed with exit code 1 (use -v to see invocation)
```
Relevant assembly snippet:
```
$ llvm-objdump -dr test.o
...
Disassembly of section .text:

00000000 <OUTLINED_FUNCTION_0>:
       0: 00092583      lw a1, 0x0(s2)
                        00000000:  R_RISCV_PCREL_LO12_I .Lpcrel_hi0
                        00000000:  R_RISCV_RELAX *ABS*
       4: 0009a603      lw      a2, 0x0(s3)
 00000004:  R_RISCV_PCREL_LO12_I .Lpcrel_hi1
 00000004:  R_RISCV_RELAX        *ABS*
...
Disassembly of section .text.unlikely.:

00000000 <main>:
...
0000001a <.Lpcrel_hi0>:
      1a: 00000917      auipc   s2, 0x0
 0000001a:  R_RISCV_PCREL_HI20   a1
 0000001a:  R_RISCV_RELAX        *ABS*
      1e: 00a92023      sw      a0, 0x0(s2)
                        0000001e:  R_RISCV_PCREL_LO12_S .Lpcrel_hi0
                        0000001e:  R_RISCV_RELAX *ABS*
...
00000036 <.Lpcrel_hi1>:
      36: 00000997      auipc s3, 0x0
                        00000036:  R_RISCV_PCREL_HI20   a2
 00000036:  R_RISCV_RELAX        *ABS*
      3a: 00a9a023      sw      a0, 0x0(s3)
                        0000003a: R_RISCV_PCREL_LO12_S .Lpcrel_hi1
                        0000003a: R_RISCV_RELAX        *ABS*
...
```
After 6b11573b8c5e3d36beee099dbe7347c2a007bf53 (though I don't think that commit is actually the problem here) `main` seems to be marked as cold and ultimately placed in `.text.unlikely` (and contains the pcrel_hi) but the outlined function with the pcrel_lo is placed into `.text`. My understanding is that GNU ld erroring here is expected based on https://reviews.llvm.org/D132528.

As a quick fix for this, I think we can take an approach similar to https://reviews.llvm.org/D132528 and make sure that functions that will be prefixed (with unlikely, unknown, etc.) will also be disallowed for outlining when the outlining candidate contains pcrel_lo.

I'm planning to try to submit a PR for this soon, but any suggestions/thoughts/etc. would be greatly appreciated!
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJycV19z26oS_zT4ZccehCzbevCDE9f3Zian7aSnnfuWQbC2aBDoAnLi8-nPgOR_aZuTHk1GwWh3WX6_3WXh3qudQVyS4oYw9t0aHmprWjTqhTBGivWId6G2bnn1aVRZeVh-1sg9gkeECrV9hq11wME3XOux8jU4bJ2VnUAHwYLExhofHA8IoUZQ3nc4gTvgDQT0QZkdPKtQw_39tz-g6pQOwAOgxCmVPNsuRIZlNqNZVS4KIXPG5XxRcL5Y0NliQYEbCf_5-BW0hK2zDVTKdEFpD3s2ycsJoWtCV8N7Roe__iebguAheTERx7lcGaE7iUDyWx-kspOa5B9-8VWr6vJzeisTYJ8ByddASX5zMcnSZHaaPH8ibMWzK-E4w34i2XBlCFvEIXc7QdgtiJq7KB9V3G5PWDkozQdtAN77EymygrCFV3-h3fZ2CCujNrComJ9V2G-rbFunTIgyPkh0LjoXw4kVkhS3Jg1vgb5SstH5tCF1Ai0Nb49ogSLsJv2VcLEpgNN6wyrwaimekeJmn5FinX6x869LD95rh13ZYT_YIfP1Efj1RYRpbnYwHgfudhhIvnbKi33OxlqZ7mW8Mx2MG14pkq-VbnMG47E_eGdtlCVs0_JQE7YJlrBNUiVsMwjAeLwTYhys1aKOcfGDwk6INBwEhlCH8ae_jg5uQtPGN_owLvhsKnFiSb4CZWDbGRGUNUBm9NPXP-_vPn5YP26-frz98-7Tx0dK2JzkQ2QOKZSvCFtMAr4Ewm7oyzThswLJzQ6d7Tw41FbwaDTOE1a0wqF-1BYa5X0sBQ0Poo6D08da9WskIKMaOmddHGhlntCBsE0Tq8CWK42yLyb4ogIIKxGyGF2dRxjvYzmKZUuZ_dGLU65cl4YH1LjnMce8x6bSB_BGtW3k79e1ROt9M7bVd9k1LYyl69G2vcBkMpSitfIno3YLHnuMe9RO1tObDk_MhZ8RkH84KUD_0AgLpbRkxSLvp_RzDN-Ydy80ZiY77Rl-8RyXjbbg4fHh7svtt8fPtw8f7h_vP2Xs8Q4m90dq6L8w9fDhfvW_WD9WN19i2bq0MD1ugM_oeQPp4exiF_l5F8MS0_e4m72l0_s1PK_cexd9k85o9YT6MHmDyFTAL5g7We5FMh6FLgH-geWMDyBRWmbzAZxOtQIA_Amky432Gq_A-e8do1Eze0v0LUwGb7D3hpeMsoEyf6SM_ovA6w3-jMkvvxt4r0z9NPBe4Z_PrvHPfsQ_n53xL6_wj2F5if6bzvVmfkEKuyLlleg_k5LzIyn8bVLyd5LSG_wHTrLft_SunHtVa1fbgA5mVZYV87xaiAJzmc8qRKRlKSuc59O5YJzSebUt8lj-Q227XQ13IGPJnwcItTJPEGoe0umhAigPXISOa31IbWrrbKWxgRodpr5jRlPmzmg8Qhofz5IKoeHuCSVwD8JqmZrRTgfV8ID6AK3mAmU8S8mMXpeIaIiwRVQQ1gSujO_XPZ55rISqC2nOdkErg_J8Iqcz7iyubfT_tFqwp_Xif_jjAJ2R6HzgRsazVfl-70PfnA7UOB83Gz_iS4sioISKe5RgDdQhtD6d75vYh-Be4bOfxBNvYt2OsM06y1nBFlf99soDh_93SjzBVr2kTi_UysfwuxsoeEYQ3EDgTwjcAG9bZ7mowatGaZ4uEO9dOoHfREO-c9hv8AjYsN9npXVkrXW4VS8Y-7xFgvLECruFzjwZ-2ziEIOYRCKSHtc-US6Vjz3xc-TDuoGcdIup0VzwFadEBFzGq8-J5CNjV0jdETZvIoEmqQULwR1Su9JVMTo5fH444Qfe2uRejA9uDuC73S7epKzxsZVLwR7iMPoPz7bTMjq-c8iDPiSQUSgeUBKWjeQyl2Ve8hEuszkrinJRZrNRvZzTki7oLJ_KnMtcClZmBZPTBee8nM-325FaMsqmtKQzWtCsmE2KPM-yaratsoqLLZZkSrHhSp_IGqXL3zKj84LRkeYVaj_cQSsuntBIkq9iYRh_G66hbpm6qqrbeTKlWvlwpn4UVNDpDjuoFGv41KeKS1GVEgJarlyi-txPxkg6t57KgFTbLTo04Xigx1bVx0yO2WJSp9mniU809Ikz6pxeXofnToW6qybCNoRtoqPDv3Hr7HcUgbBNwiCyM8CwX7K_AwAA__8OB2vB">