add test for codegen of SIMD vector from array repeat

tests/codegen-llvm/simd/array-repeat.rs

@@ -0,0 +1,40 @@
+//@ add-minicore
+//@ revisions: X86 AARCH64 RISCV S390X
+//@ [X86] compile-flags: -Copt-level=3 --target=x86_64-unknown-linux-gnu
+//@ [X86] needs-llvm-components: x86
+//@ [AARCH64] compile-flags: -Copt-level=3 --target=aarch64-unknown-linux-gnu
+//@ [AARCH64] needs-llvm-components: aarch64
+//@ [RISCV] compile-flags: -Copt-level=3 --target riscv64gc-unknown-linux-gnu -Ctarget-feature=+v
+//@ [RISCV] needs-llvm-components: riscv
+//@ [S390X] compile-flags: -Copt-level=3 --target s390x-unknown-linux-gnu -Ctarget-feature=+vector
+//@ [S390X] needs-llvm-components: systemz
+#![crate_type = "lib"]
+#![feature(repr_simd)]
+#![feature(no_core)]
+#![no_std]
+#![no_core]
+extern crate minicore;
+use minicore::*;
+
+#[repr(simd)]
+pub struct Simd<T, const N: usize>(pub [T; N]);
+
+pub type u8x16 = Simd<u8, 16>;
+
+// Regression test for https://github.com/rust-lang/rust/issues/97804.
+
+#[unsafe(no_mangle)]
+fn foo(v: u16, p: &mut [u8; 16]) {
+    // An array repeat transmuted into a SIMD type should emit a canonical LLVM splat sequence:
+    //
+    // CHECK-LABEL: foo
+    // CHECK: start
+    // CHECK-NEXT: %0 = insertelement <8 x i16> poison, i16 %v, i64 0
+    // CHECK-NEXT: %1 = shufflevector <8 x i16> %0, <8 x i16> poison, <8 x i32> zeroinitializer
+    // CHECK-NEXT: store <8 x i16> %1, ptr %p, align 1
+    // CHECK-NEXT: ret void
+    unsafe {
+        let v: u8x16 = mem::transmute([v; 8]);
+        *p = mem::transmute(v);
+    }
+}