Commit 5c82a59

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Add test and comment

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Lines changed: 5 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -128,6 +128,11 @@ pub(crate) fn const_alloc_to_llvm<'ll>(`
`128`	`128`	`append_chunks_of_init_and_uninit_bytes(&mut llvals, cx, alloc, range);`
`129`	`129`	`}`
`130`	`130`
	`131`	`+ // Avoid wrapping in a struct if there is only a single value. This ensures`
	`132`	`+ // that LLVM is able to perform the string merging optimization if the constant`
	`133`	`+ // is a valid C string. LLVM only considers bare arrays for this optimization,`
	`134`	`+ // not arrays wrapped in a struct. LLVM handles this at:`
	`135`	`+ // https://github.com/rust-lang/llvm-project/blob/acaea3d2bb8f351b740db7ebce7d7a40b9e21488/llvm/lib/Target/TargetLoweringObjectFile.cpp#L249-L280`
`131`	`136`	`if let &[data] = &*llvals { data } else { cx.const_struct(&llvals, true) }`
`132`	`137`	`}`
`133`	`138`

Lines changed: 27 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,27 @@`
	`1`	`+//@ only-linux`
	`2`	`+//@ assembly-output: emit-asm`
	`3`	`+//@ compile-flags: --crate-type=lib -Copt-level=3 --edition 2024`
	`4`	`+`
	`5`	`+use std::ffi::CStr;`
	`6`	`+`
	`7`	`+// CHECK: .section .rodata.str1.1,"aMS"`
	`8`	`+// CHECK: .Lanon.{{.+}}:`
	`9`	`+// CHECK-NEXT: .asciz "foo"`
	`10`	`+#[unsafe(no_mangle)]`
	`11`	`+static CSTR: &[u8; 4] = b"foo0円";`
	`12`	`+`
	`13`	`+// CHECK-NOT: .section`
	`14`	`+// CHECK: .Lanon.{{.+}}:`
	`15`	`+// CHECK-NEXT: .asciz "bar"`
	`16`	`+#[unsafe(no_mangle)]`
	`17`	`+pub fn cstr() -> &'static CStr {`
	`18`	`+ c"bar"`
	`19`	`+}`
	`20`	`+`
	`21`	`+// CHECK-NOT: .section`
	`22`	`+// CHECK: .Lanon.{{.+}}:`
	`23`	`+// CHECK-NEXT: .asciz "baz"`
	`24`	`+#[unsafe(no_mangle)]`
	`25`	`+pub fn manual_cstr() -> &'static str {`
	`26`	`+ "baz0円"`
	`27`	`+}`

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