tree e2c4614aee4d26ac9fb6611b2da5ad75d90a4793
parent ef2ca97f48f1aee1483f0c29de5ba52979bec454
author Fangrui Song <i@maskray.me> 1714062475 -0700
committer GitHub <noreply@github.com> 1714062475 -0700
gpgsig -----BEGIN PGP SIGNATURE-----
 
 wsFcBAABCAAQBQJmKoSLCRC1aQ7uu5UhlAAAA2cQAIMGRi1weybHSvtLyJbZjKhK
 oZ1jk/HLAkBkudjrbsAS3UdpwH21Taaihra+oX6E24N3RhuLpxNm3J3VkJz6mtm1
 KXFreJllkCEeyypJisVOVEvkhKkiieLfBl/gkzcpnwgY3pKnSb6rLsMAIo/O5j6w
 qKj3kWL22CERVw6k7U98lnf5k0yuGxsW1ZmDtqAVsgneBTv608pJfZfprlLroRfd
 Cb9Se2N2lccrRUW31dNpT6JwsmxZYh7zqNG9LqxAIUeuAhULXPvoDWD3hgMSMfkl
 XYBzGCYLPhAxoEZu+dbnqyuOUxlipusxi7l70brLbyHSP/3obk3S799ulbf+QcoF
 cY2g/VPnbQLYYj7QNT7gAB3BFVc8FF81TUJZwbwAmLhjVcJOKUWBnlxtc7stXiOZ
 Ldf39Sn7T2NLsUwQxLDRPk+Ry8EosigMhSSZsvhiNGJ7nyq+PB0QUuU8UqCVJb67
 eOBfRcBBXNawoYdftnJab0zCRlxVCgO3WhGYw1fbjPfyrxbwifKNVMI5pSz21Q2P
 RWwjCkoHkIka29oenr4NlHbk9chDBEc5RsZzu3Al3oHOZwm2xF/r1PETkcyT3I8N
 D7ybbm+BQ5dmkdNGv5w1DwNLJ8KV4l4oV+3noXJoU5MgD/pTUHIvMmJb3PlBwEcg
 lxJySjJWkepPWjUMiUz0
 =+nX8
 -----END PGP SIGNATURE-----
 

[Driver] Don't default to -mrelax-all for non-RISCV -O0

Some assembly mnemonics may assemble to instructions of different
lengths. The longer form is to support instructions like a long branch.
On X86, -mrelax-all enables `MCRelaxAll`, which expands instructions to
the long form regardless of whether a short form suffices, while
-mno-relax-all only expands instructions when needed.

```
// x86 example
void foo(int a) {
  // -mno-relax-all or gas: short jump (2 bytes)
  // -mrelax-all: near jump (6 bytes)
  if (a) bar();
}
```

The -mrelax-all default for non-RISCV -O0 appears to only affect x86 and
increases code size without any compile time difference for a stage-2
x86-64 build of lld.
```
-mrelax-all:    file size: 60.9MiB   VM size: 52.4MiB
-mno-relax-all: file size: 58.2MiB   VM size: 49.7MiB
```

There is no compile time difference (other than noise) GNU assembler
doesn't expand instructions by default. Let's remove the -mrelax-all default.

Pull Request: https://github.com/llvm/llvm-project/pull/90013