diff --git a/src/doc/rustc-dev-guide/src/tests/directives.md b/src/doc/rustc-dev-guide/src/tests/directives.md
index 34d25b1d6dbc2..4ae5a4144fb81 100644
--- a/src/doc/rustc-dev-guide/src/tests/directives.md
+++ b/src/doc/rustc-dev-guide/src/tests/directives.md
@@ -133,7 +133,7 @@ means the test won't be compiled or run.
 Some examples of `X` in `ignore-X` or `only-X`:
 
 - A full target triple: `aarch64-apple-ios`
-- Architecture: `aarch64`, `arm`, `mips`, `wasm32`, `x86_64`, `x86`,
+- Architecture: `aarch64`, `arm`, `csky`, `mips`, `mips64`, `wasm32`, `x86_64`, `x86`,
   ...
 - OS: `android`, `emscripten`, `freebsd`, `ios`, `linux`, `macos`, `windows`,
   ...
diff --git a/src/tools/compiletest/src/directives/directive_names.rs b/src/tools/compiletest/src/directives/directive_names.rs
index e1b6e70d90f04..72e9787fe42ec 100644
--- a/src/tools/compiletest/src/directives/directive_names.rs
+++ b/src/tools/compiletest/src/directives/directive_names.rs
@@ -67,6 +67,7 @@ pub(crate) const KNOWN_DIRECTIVE_NAMES: &[&str] = &[
     "ignore-coverage-map",
     "ignore-coverage-run",
     "ignore-cross-compile",
+    "ignore-csky",
     "ignore-eabi",
     "ignore-elf",
     "ignore-emscripten",
@@ -91,6 +92,8 @@ pub(crate) const KNOWN_DIRECTIVE_NAMES: &[&str] = &[
     "ignore-loongarch64",
     "ignore-macabi",
     "ignore-macos",
+    "ignore-mips",
+    "ignore-mips64",
     "ignore-msp430",
     "ignore-msvc",
     "ignore-musl",
diff --git a/tests/ui/explicit-tail-calls/become-indirect-return.rs b/tests/ui/explicit-tail-calls/become-indirect-return.rs
index b1e552bca0293..8cf733dbfdff5 100644
--- a/tests/ui/explicit-tail-calls/become-indirect-return.rs
+++ b/tests/ui/explicit-tail-calls/become-indirect-return.rs
@@ -2,6 +2,27 @@
 //@ ignore-backends: gcc
 //@ ignore-wasm 'tail-call' feature not enabled in target wasm32-wasip1
 //@ ignore-cross-compile
+//
+// LLVM musttail support is incomplete for these targets.
+// See https://github.com/rust-lang/rust/issues/148748 for the target test matrix.
+// See https://github.com/llvm/llvm-project/issues/63214 for AIX and PowerPC.
+// See https://github.com/llvm/llvm-project/issues/57795 for MIPS and MIPS64.
+//@ ignore-aix
+//@ ignore-csky
+//@ ignore-mips
+//@ ignore-mips64
+//@ ignore-powerpc
+//@ ignore-powerpc64
+//
+// LLVM musttail support is lacking for sret lowering on these targets.
+// Returning `[u8; 24]` uses sret lowering here.
+// See https://github.com/llvm/llvm-project/issues/157814 for RISC-V.
+// See https://github.com/llvm/llvm-project/issues/168152 for LoongArch.
+// RISC-V fix: https://github.com/llvm/llvm-project/pull/185094, should be in LLVM 23.
+// LoongArch will likely be fixed with similar changes.
+//@ ignore-riscv64
+//@ ignore-loongarch32
+//@ ignore-loongarch64
 #![expect(incomplete_features)]
 #![feature(explicit_tail_calls)]
 
diff --git a/tests/ui/explicit-tail-calls/indirect.rs b/tests/ui/explicit-tail-calls/indirect.rs
index 537976b7f6f43..b3e2613efad25 100644
--- a/tests/ui/explicit-tail-calls/indirect.rs
+++ b/tests/ui/explicit-tail-calls/indirect.rs
@@ -2,7 +2,26 @@
 //@ ignore-backends: gcc
 //
 //@ ignore-wasm
+//
+// LLVM musttail support is incomplete for these targets.
+// See https://github.com/rust-lang/rust/issues/148748 for the target test matrix.
+// See https://github.com/llvm/llvm-project/issues/63214 for AIX and PowerPC.
+// See https://github.com/llvm/llvm-project/issues/57795 for MIPS and MIPS64.
+//@ ignore-aix
+//@ ignore-csky
+//@ ignore-mips
+//@ ignore-mips64
+//@ ignore-powerpc
+//@ ignore-powerpc64
+//
+// LLVM musttail support is lacking for indirect arguments that do not fit in registers.
+// See https://github.com/llvm/llvm-project/issues/157814 for RISC-V.
+// See https://github.com/llvm/llvm-project/issues/168152 for LoongArch.
+// RISC-V fix: https://github.com/llvm/llvm-project/pull/185094, should be in LLVM 23.
+// LoongArch will likely be fixed with similar changes.
 //@ ignore-riscv64
+//@ ignore-loongarch32
+//@ ignore-loongarch64
 #![feature(explicit_tail_calls)]
 #![expect(incomplete_features)]