No branch protection metadata unless enabled

Even if we emit metadata disabling branch protection, this metadata may
conflict with other modules (e.g. during LTO) that have different branch
protection metadata set.

This is an unstable flag and feature, so ideally the flag not being
specified should act as if the feature wasn't implemented in the first
place.

Additionally this PR also ensures we emit an error if
`-Zbranch-protection` is set on targets other than the supported
aarch64. For now the error is being output from codegen, but ideally it
should be moved to earlier in the pipeline before stabilization.

4 files changed, 47 insertions, 25 deletions

diff --git a/src/test/codegen/branch-protection.rs b/src/test/codegen/branch-protection.rs
index 106c9b148ee..b23073778c0 100644
--- a/src/test/codegen/branch-protection.rs
+++ b/src/test/codegen/branch-protection.rs
@@ -1,12 +1,12 @@
 // Test that the correct module flags are emitted with different branch protection flags.
 
-// revisions: bti pac-ret leaf b-key
+// revisions: BTI PACRET LEAF BKEY NONE
 // min-llvm-version: 12.0.0
 // needs-llvm-components: aarch64
-// [bti] compile-flags: -Z branch-protection=bti
-// [pac-ret] compile-flags: -Z branch-protection=pac-ret
-// [leaf] compile-flags: -Z branch-protection=pac-ret,leaf
-// [b-key] compile-flags: -Z branch-protection=pac-ret,b-key
+// [BTI] compile-flags: -Z branch-protection=bti
+// [PACRET] compile-flags: -Z branch-protection=pac-ret
+// [LEAF] compile-flags: -Z branch-protection=pac-ret,leaf
+// [BKEY] compile-flags: -Z branch-protection=pac-ret,b-key
 // compile-flags: --target aarch64-unknown-linux-gnu
 
 #![crate_type = "lib"]
@@ -20,22 +20,27 @@ trait Sized { }
 pub fn test() {
 }
 
-// bti: !"branch-target-enforcement", i32 1
-// bti: !"sign-return-address", i32 0
-// bti: !"sign-return-address-all", i32 0
-// bti: !"sign-return-address-with-bkey", i32 0
-
-// pac-ret: !"branch-target-enforcement", i32 0
-// pac-ret: !"sign-return-address", i32 1
-// pac-ret: !"sign-return-address-all", i32 0
-// pac-ret: !"sign-return-address-with-bkey", i32 0
-
-// leaf: !"branch-target-enforcement", i32 0
-// leaf: !"sign-return-address", i32 1
-// leaf: !"sign-return-address-all", i32 1
-// leaf: !"sign-return-address-with-bkey", i32 0
-
-// b-key: !"branch-target-enforcement", i32 0
-// b-key: !"sign-return-address", i32 1
-// b-key: !"sign-return-address-all", i32 0
-// b-key: !"sign-return-address-with-bkey", i32 1
+// BTI: !"branch-target-enforcement", i32 1
+// BTI: !"sign-return-address", i32 0
+// BTI: !"sign-return-address-all", i32 0
+// BTI: !"sign-return-address-with-bkey", i32 0
+
+// PACRET: !"branch-target-enforcement", i32 0
+// PACRET: !"sign-return-address", i32 1
+// PACRET: !"sign-return-address-all", i32 0
+// PACRET: !"sign-return-address-with-bkey", i32 0
+
+// LEAF: !"branch-target-enforcement", i32 0
+// LEAF: !"sign-return-address", i32 1
+// LEAF: !"sign-return-address-all", i32 1
+// LEAF: !"sign-return-address-with-bkey", i32 0
+
+// BKEY: !"branch-target-enforcement", i32 0
+// BKEY: !"sign-return-address", i32 1
+// BKEY: !"sign-return-address-all", i32 0
+// BKEY: !"sign-return-address-with-bkey", i32 1
+
+// NONE-NOT: branch-target-enforcement
+// NONE-NOT: sign-return-address
+// NONE-NOT: sign-return-address-all
+// NONE-NOT: sign-return-address-with-bkey
diff --git a/src/test/ui/invalid-compile-flags/branch-protection-missing-pac-ret.stderr b/src/test/ui/invalid-compile-flags/branch-protection-missing-pac-ret.BADFLAGS.stderr
index 5528d2a0729..5528d2a0729 100644
--- a/src/test/ui/invalid-compile-flags/branch-protection-missing-pac-ret.stderr
+++ b/src/test/ui/invalid-compile-flags/branch-protection-missing-pac-ret.BADFLAGS.stderr
diff --git a/src/test/ui/invalid-compile-flags/branch-protection-missing-pac-ret.BADTARGET.stderr b/src/test/ui/invalid-compile-flags/branch-protection-missing-pac-ret.BADTARGET.stderr
new file mode 100644
index 00000000000..6bd9c6a0276
--- /dev/null
+++ b/src/test/ui/invalid-compile-flags/branch-protection-missing-pac-ret.BADTARGET.stderr
@@ -0,0 +1,4 @@
+error: -Zbranch-protection is only supported on aarch64
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/invalid-compile-flags/branch-protection-missing-pac-ret.rs b/src/test/ui/invalid-compile-flags/branch-protection-missing-pac-ret.rs
index 4f39d223a2e..4bc4919bc93 100644
--- a/src/test/ui/invalid-compile-flags/branch-protection-missing-pac-ret.rs
+++ b/src/test/ui/invalid-compile-flags/branch-protection-missing-pac-ret.rs
@@ -1 +1,14 @@
-// compile-flags: -Z branch-protection=leaf
+// revisions: BADFLAGS BADTARGET
+// [BADFLAGS] compile-flags: --target=aarch64-unknown-linux-gnu -Zbranch-protection=leaf
+// [BADFLAGS] check-fail
+// [BADFLAGS] needs-llvm-components: aarch64
+// [BADTARGET] compile-flags: --target=x86_64-unknown-linux-gnu -Zbranch-protection=bti
+// [BADTARGET] build-fail
+// [BADTARGET] needs-llvm-components: x86
+
+#![crate_type = "lib"]
+#![feature(no_core, lang_items)]
+#![no_core]
+
+#[lang="sized"]
+trait Sized { }