2 files changed, 22 insertions, 7 deletions
diff --git a/compiler/rustc_target/src/asm/mod.rs b/compiler/rustc_target/src/asm/mod.rs
index 10778e9acf1..db8d23776e5 100644
--- a/compiler/rustc_target/src/asm/mod.rs
+++ b/compiler/rustc_target/src/asm/mod.rs
@@ -604,9 +604,13 @@ impl InlineAsmRegClass {
 
     /// Returns a list of supported types for this register class, each with an
     /// options target feature required to use this type.
+    ///
+    /// At the codegen stage, it is fine to always pass true for `allow_experimental_reg`,
+    /// since all the stability checking will have been done in prior stages.
     pub fn supported_types(
         self,
         arch: InlineAsmArch,
+        allow_experimental_reg: bool,
     ) -> &'static [(InlineAsmType, Option<Symbol>)] {
         match self {
             Self::X86(r) => r.supported_types(arch),
@@ -618,7 +622,7 @@ impl InlineAsmRegClass {
             Self::Hexagon(r) => r.supported_types(arch),
             Self::LoongArch(r) => r.supported_types(arch),
             Self::Mips(r) => r.supported_types(arch),
-            Self::S390x(r) => r.supported_types(arch),
+            Self::S390x(r) => r.supported_types(arch, allow_experimental_reg),
             Self::Sparc(r) => r.supported_types(arch),
             Self::SpirV(r) => r.supported_types(arch),
             Self::Wasm(r) => r.supported_types(arch),
@@ -696,8 +700,11 @@ impl InlineAsmRegClass {
 
     /// Returns whether registers in this class can only be used as clobbers
     /// and not as inputs/outputs.
-    pub fn is_clobber_only(self, arch: InlineAsmArch) -> bool {
-        self.supported_types(arch).is_empty()
+    ///
+    /// At the codegen stage, it is fine to always pass true for `allow_experimental_reg`,
+    /// since all the stability checking will have been done in prior stages.
+    pub fn is_clobber_only(self, arch: InlineAsmArch, allow_experimental_reg: bool) -> bool {
+        self.supported_types(arch, allow_experimental_reg).is_empty()
     }
 }
 
diff --git a/compiler/rustc_target/src/asm/s390x.rs b/compiler/rustc_target/src/asm/s390x.rs
index 426417e5bac..410590b722b 100644
--- a/compiler/rustc_target/src/asm/s390x.rs
+++ b/compiler/rustc_target/src/asm/s390x.rs
@@ -38,14 +38,22 @@ impl S390xInlineAsmRegClass {
     pub fn supported_types(
         self,
         _arch: InlineAsmArch,
+        allow_experimental_reg: bool,
     ) -> &'static [(InlineAsmType, Option<Symbol>)] {
         match self {
             Self::reg | Self::reg_addr => types! { _: I8, I16, I32, I64; },
             Self::freg => types! { _: F32, F64; },
-            Self::vreg => types! {
-                vector: I32, F32, I64, F64, I128, F128,
-                    VecI8(16), VecI16(8), VecI32(4), VecI64(2), VecF32(4), VecF64(2);
-            },
+            Self::vreg => {
+                if allow_experimental_reg {
+                    // non-clobber-only vector register support is unstable.
+                    types! {
+                        vector: I32, F32, I64, F64, I128, F128,
+                            VecI8(16), VecI16(8), VecI32(4), VecI64(2), VecF32(4), VecF64(2);
+                    }
+                } else {
+                    &[]
+                }
+            }
             Self::areg => &[],
         }
     }