[PATCH 05/11] rust: Do not pass the removed x86 amx-tf32 feature to LLVM 23

[sunilkumar.dora@windriver.com]

From: Sunil Dora <sunilkumar.dora@windriver.com>

LLVM 23 removed the x86 amx-tf32 subtarget feature, so a rustc built
against LLVM 23 aborts at startup with

  "+amx-tf32" is not a recognized feature for this target

Gate the feature out of to_llvm_features for LLVM >= 23. rust dropped
the feature entirely after 1.98
(https://github.com/rust-lang/rust/pull/159310), but backporting that
would change stable rust behaviour, while a version guard keeps this
rust working against older LLVM majors too.

Signed-off-by: Sunil Dora <sunilkumar.dora@windriver.com>
---
 ...llvm-Do-not-pass-amx-tf32-to-LLVM-23.patch | 38 +++++++++++++++++++
 meta/recipes-devtools/rust/rust-source.inc    |  1 +
 2 files changed, 39 insertions(+)
 create mode 100644 meta/recipes-devtools/rust/files/0005-rustc_codegen_llvm-Do-not-pass-amx-tf32-to-LLVM-23.patch

diff --git a/meta/recipes-devtools/rust/files/0005-rustc_codegen_llvm-Do-not-pass-amx-tf32-to-LLVM-23.patch b/meta/recipes-devtools/rust/files/0005-rustc_codegen_llvm-Do-not-pass-amx-tf32-to-LLVM-23.patch
new file mode 100644
index 0000000000..99fcd334c7
--- /dev/null
+++ b/meta/recipes-devtools/rust/files/0005-rustc_codegen_llvm-Do-not-pass-amx-tf32-to-LLVM-23.patch
@@ -0,0 +1,38 @@
+From: Sunil Dora <sunilkumar.dora@windriver.com>
+Date: Wed, 26 Aug 2026 16:30:00 +0530
+Subject: [PATCH] rustc_codegen_llvm: do not pass amx-tf32 to LLVM 23
+
+LLVM 23 removed the x86 amx-tf32 subtarget feature
+(https://github.com/llvm/llvm-project/pull/207673). rust 1.98 still
+lists it in the x86 table in rustc_target, so a rustc built against
+LLVM 23 aborts at startup with
+
+  '+amx-tf32' is not a recognized feature for this target
+
+Skip the feature in to_llvm_features when the LLVM in use is 23 or
+newer, in the same style the surrounding code already uses for
+avx10.1/avx10.2 on older LLVM majors. amx-tf32 is the only x86
+feature LLVM 23 removed; the rest of the table still matches X86.td.
+
+rust dropped the feature outright after 1.98
+(https://github.com/rust-lang/rust/pull/159310), which requires
+LLVM 23 or newer unconditionally. This recipe builds against whatever
+LLVM major the layer provides, so the version guard is kept instead.
+
+Upstream-Status: Inappropriate [rust dropped the feature after 1.98 via https://github.com/rust-lang/rust/pull/159310; this guard only exists to build 1.98 against more than one LLVM major]
+Signed-off-by: Sunil Dora <sunilkumar.dora@windriver.com>
+---
+ compiler/rustc_codegen_llvm/src/llvm_util.rs | 2 ++
+ 1 file changed, 2 insertions(+)
+
+--- a/compiler/rustc_codegen_llvm/src/llvm_util.rs
++++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs
+@@ -286,6 +286,8 @@
+                     s,
+                     smallvec![TargetFeatureFoldStrength::EnableOnly("evex512")],
+                 )),
++                // AMX-TF32 was removed from LLVM 23
++                "amx-tf32" if major >= 23 => None,
+                 "avx10.1" if major < 22 => Some(LLVMFeature::new("avx10.1-512")),
+                 "avx10.2" if major < 22 => Some(LLVMFeature::new("avx10.2-512")),
+                 "apxf" => Some(LLVMFeature::with_dependencies(
diff --git a/meta/recipes-devtools/rust/rust-source.inc b/meta/recipes-devtools/rust/rust-source.inc
index d87271b29c..f40f1652b2 100644
--- a/meta/recipes-devtools/rust/rust-source.inc
+++ b/meta/recipes-devtools/rust/rust-source.inc
@@ -8,6 +8,7 @@ SRC_URI += "https://static.rust-lang.org/dist/rustc-${RUST_VERSION}-src.tar.xz;n
             file://0002-Fix-rust-build-failure-with-unstable-options.patch;patchdir=${RUSTSRC} \
             file://0003-bootstrap-skip-StdarchVerify-when-remote-testing.patch;patchdir=${RUSTSRC} \
             file://0004-Backport-commits-from-rust-Fix-selftest-llvm23.patch;patchdir=${RUSTSRC} \
+            file://0005-rustc_codegen_llvm-Do-not-pass-amx-tf32-to-LLVM-23.patch;patchdir=${RUSTSRC} \
 "
 SRC_URI[rust.sha256sum] = "271fa73d8174f53d713c46a8310da7bf7cfdcfb8b7cfd1c2b74b84a83ae9fb1e"
 
-- 
2.43.0