Auto merge of #112910 - lqd:mcp510, r=petrochenkov

Implement most of MCP510

This implements most of what remains to be done for MCP510:
- turns `-C link-self-contained` into a `+`/`-` list of components, like `-C link-self-contained=+linker,+crto,+libc,+unwind,+sanitizers,+mingw`. The scaffolding is present for all these expected components to be implemented and stabilized in the future on their own time. This PR only handles the `-Zgcc-ld=lld` subset of these link-self-contained components as  `-Clink-self-contained=+linker`
- handles  `-C link-self-contained=y|n`  as-is today, for compatibility with `rustc_codegen_ssa::back::link::self_contained`'s [explicit opt-in and opt-out](https://github.com/lqd/rust/blob/9eee230cd0a56bfba3ce65121798d9f9f4341cdd/compiler/rustc_codegen_ssa/src/back/link.rs#L1671-L1676).
- therefore supports our plan to opt out of `rust-lld` (when it's enabled by default) even for current `-Clink-self-contained` users, with e.g. `-Clink-self-contained -Clink-self-contained=-linker`
- turns `add_gcc_ld_path` into its expected final form, by using the `-C link-self-contained=+linker`  CLI flag, and whether the `LinkerFlavor`  has the expected `Cc::Yes` and `Lld::Yes` shape (this is not yet the case in practice for any CLI linker flavor)
- makes the [new clean linker flavors](https://github.com/rust-lang/rust/pull/96827#issuecomment-1208441595) selectable in the CLI in addition to the legacy ones, in order to opt-in to using `cc` and `lld` to emulate `-Zgcc-ld=lld`
- ensure the new `-C link-self-contained` components, and `-C linker-flavor`s are unstable, and require `-Z unstable-options` to be used

The up-to-date set of flags for the future stable CLI version of `-Zgcc-ld=lld` is currently: `-Clink-self-contained=+linker -Clinker-flavor=gnu-lld-cc -Zunstable-options`.

It's possible we'll also need to do something for distros that don't ship `rust-lld`, but maybe there are already no tool search paths to be added to `cc` in this situation anyways.

r? `@petrochenkov`

6 files changed, 21 insertions, 5 deletions

diff --git a/tests/run-make/rust-lld/Makefile b/tests/run-make/rust-lld/Makefile
new file mode 100644
index 00000000000..f8526530d4d
--- /dev/null
+++ b/tests/run-make/rust-lld/Makefile
@@ -0,0 +1,8 @@
+include ../tools.mk
+
+# ignore-msvc
+# needs-rust-lld
+# ignore-s390x lld does not yet support s390x as target
+all:
+	RUSTC_LOG=rustc_codegen_ssa::back::link=info $(RUSTC) -Clink-self-contained=+linker -Clinker-flavor=gnu-lld-cc -Zunstable-options -Clink-args=-Wl,-v main.rs 2> $(TMPDIR)/output.txt
+	$(CGREP) -e "^LLD [0-9]+\.[0-9]+\.[0-9]+" < $(TMPDIR)/output.txt
diff --git a/tests/run-make/rust-lld/main.rs b/tests/run-make/rust-lld/main.rs
new file mode 100644
index 00000000000..bf159cd941c
--- /dev/null
+++ b/tests/run-make/rust-lld/main.rs
@@ -0,0 +1,4 @@
+// Test linking using `cc` with `rust-lld`, using the unstable CLI described in MCP 510
+// see https://github.com/rust-lang/compiler-team/issues/510 for more info
+
+fn main() {}
diff --git a/tests/ui/linkage-attr/incompatible-flavor.stderr b/tests/ui/linkage-attr/incompatible-flavor.stderr
index e07e778521c..aabdd14b69b 100644
--- a/tests/ui/linkage-attr/incompatible-flavor.stderr
+++ b/tests/ui/linkage-attr/incompatible-flavor.stderr
@@ -1,6 +1,6 @@
 error: linker flavor `msvc` is incompatible with the current target
    |
-   = note: compatible flavors are: gcc, ld, ld.lld
+   = note: compatible flavors are: gnu, gnu-lld, gnu-cc, gnu-lld-cc, gcc, ld, ld.lld
 
 error: aborting due to previous error
 
diff --git a/tests/ui/linkage-attr/unstable-flavor.bpf.stderr b/tests/ui/linkage-attr/unstable-flavor.bpf.stderr
index 3346d12c20e..594a461769b 100644
--- a/tests/ui/linkage-attr/unstable-flavor.bpf.stderr
+++ b/tests/ui/linkage-attr/unstable-flavor.bpf.stderr
@@ -1,2 +1,2 @@
-error: linker flavor `bpf-linker` is unstable, `-Z unstable-options` flag must also be passed to explicitly use it
+error: the linker flavor `bpf-linker` is unstable, the `-Z unstable-options` flag must also be passed to use the unstable values
 
diff --git a/tests/ui/linkage-attr/unstable-flavor.ptx.stderr b/tests/ui/linkage-attr/unstable-flavor.ptx.stderr
index 03ca2a01246..714c09df53f 100644
--- a/tests/ui/linkage-attr/unstable-flavor.ptx.stderr
+++ b/tests/ui/linkage-attr/unstable-flavor.ptx.stderr
@@ -1,2 +1,2 @@
-error: linker flavor `ptx-linker` is unstable, `-Z unstable-options` flag must also be passed to explicitly use it
+error: the linker flavor `ptx-linker` is unstable, the `-Z unstable-options` flag must also be passed to use the unstable values
 
diff --git a/tests/ui/linkage-attr/unstable-flavor.rs b/tests/ui/linkage-attr/unstable-flavor.rs
index 5487882dc24..b58fd055fdc 100644
--- a/tests/ui/linkage-attr/unstable-flavor.rs
+++ b/tests/ui/linkage-attr/unstable-flavor.rs
@@ -1,9 +1,13 @@
+// Even though this test only checks 2 of the 10 or so unstable linker flavors, it exercizes the
+// unique codepath checking all unstable options (see `LinkerFlavorCli::is_unstable` and its
+// caller). If it passes, all the other unstable options are rejected as well.
+//
 // revisions: bpf ptx
 // [bpf] compile-flags: --target=bpfel-unknown-none -C linker-flavor=bpf-linker --crate-type=rlib
-// [bpf] error-pattern: linker flavor `bpf-linker` is unstable, `-Z unstable-options` flag
+// [bpf] error-pattern: linker flavor `bpf-linker` is unstable, the `-Z unstable-options` flag
 // [bpf] needs-llvm-components:
 // [ptx] compile-flags: --target=nvptx64-nvidia-cuda -C linker-flavor=ptx-linker --crate-type=rlib
-// [ptx] error-pattern: linker flavor `ptx-linker` is unstable, `-Z unstable-options` flag
+// [ptx] error-pattern: linker flavor `ptx-linker` is unstable, the `-Z unstable-options` flag
 // [ptx] needs-llvm-components:
 
 #![feature(no_core)]