Refactor liveness-issue-77915 to liveness-asm and improve tests

Author: oliviacrain

src/test/ui/liveness/liveness-asm.rs

@@ -0,0 +1,43 @@
+// Ensure inout asm! operands are marked as used by the liveness pass
+
+// check-pass
+
+#![feature(asm)]
+#![allow(dead_code)]
+#![warn(unused_assignments)]
+#![warn(unused_variables)]
+
+// Test the single inout case
+unsafe fn f1(mut src: *const u8) {
+    asm!("/*{0}*/", inout(reg) src); //~ WARN value assigned to `src` is never read
+}
+
+unsafe fn f2(mut src: *const u8) -> *const u8 {
+    asm!("/*{0}*/", inout(reg) src);
+    src
+}
+
+// Test the split inout case
+unsafe fn f3(mut src: *const u8) {
+    asm!("/*{0}*/", inout(reg) src => src); //~ WARN value assigned to `src` is never read
+}
+
+unsafe fn f4(mut src: *const u8) -> *const u8 {
+    asm!("/*{0}*/", inout(reg) src => src);
+    src
+}
+
+// Tests the use of field projections
+struct S {
+    field: *mut u8,
+}
+
+unsafe fn f5(src: &mut S) {
+    asm!("/*{0}*/", inout(reg) src.field);
+}
+
+unsafe fn f6(src: &mut S) {
+    asm!("/*{0}*/", inout(reg) src.field => src.field);
+}
+
+fn main() {}

src/test/ui/liveness/liveness-asm.stderr

@@ -0,0 +1,23 @@
+warning: value assigned to `src` is never read
+  --> $DIR/liveness-asm.rs:12:32
+   |
+LL |     asm!("/*{0}*/", inout(reg) src);
+   |                                ^^^
+   |
+note: the lint level is defined here
+  --> $DIR/liveness-asm.rs:7:9
+   |
+LL | #![warn(unused_assignments)]
+   |         ^^^^^^^^^^^^^^^^^^
+   = help: maybe it is overwritten before being read?
+
+warning: value assigned to `src` is never read
+  --> $DIR/liveness-asm.rs:22:39
+   |
+LL |     asm!("/*{0}*/", inout(reg) src => src);
+   |                                       ^^^
+   |
+   = help: maybe it is overwritten before being read?
+
+warning: 2 warnings emitted
+