Rollup merge of #99207 - 5225225:msan-eager-checks, r=jackh726

Enable eager checks for memory sanitizer

Fixes #99179

2 files changed, 45 insertions, 4 deletions

diff --git a/src/test/ui/sanitize/memory-eager.rs b/src/test/ui/sanitize/memory-eager.rs
new file mode 100644
index 00000000000..8a0590bf16c
--- /dev/null
+++ b/src/test/ui/sanitize/memory-eager.rs
@@ -0,0 +1,38 @@
+// needs-sanitizer-support
+// needs-sanitizer-memory
+// min-llvm-version: 14.0.0
+//
+// revisions: unoptimized optimized
+//
+// [optimized]compile-flags: -Z sanitizer=memory -Zsanitizer-memory-track-origins -O
+// [unoptimized]compile-flags: -Z sanitizer=memory -Zsanitizer-memory-track-origins
+//
+// run-fail
+// error-pattern: MemorySanitizer: use-of-uninitialized-value
+// error-pattern: Uninitialized value was created by an allocation
+// error-pattern: in the stack frame of function 'random'
+//
+// This test case intentionally limits the usage of the std,
+// since it will be linked with an uninstrumented version of it.
+
+#![feature(core_intrinsics)]
+#![feature(start)]
+#![feature(bench_black_box)]
+
+use std::hint::black_box;
+use std::mem::MaybeUninit;
+
+#[inline(never)]
+#[no_mangle]
+#[allow(invalid_value)]
+fn random() -> char {
+    let r = unsafe { MaybeUninit::uninit().assume_init() };
+    // Avoid optimizing everything out.
+    black_box(r)
+}
+
+#[start]
+fn main(_: isize, _: *const *const u8) -> isize {
+    random();
+    0
+}
diff --git a/src/test/ui/sanitize/memory.rs b/src/test/ui/sanitize/memory.rs
index adda51f6be0..14d4de65dd3 100644
--- a/src/test/ui/sanitize/memory.rs
+++ b/src/test/ui/sanitize/memory.rs
@@ -1,7 +1,10 @@
 // needs-sanitizer-support
 // needs-sanitizer-memory
 //
-// compile-flags: -Z sanitizer=memory -Zsanitizer-memory-track-origins -O
+// revisions: unoptimized optimized
+//
+// [optimized]compile-flags: -Z sanitizer=memory -Zsanitizer-memory-track-origins -O
+// [unoptimized]compile-flags: -Z sanitizer=memory -Zsanitizer-memory-track-origins
 //
 // run-fail
 // error-pattern: MemorySanitizer: use-of-uninitialized-value
@@ -22,9 +25,9 @@ use std::mem::MaybeUninit;
 #[inline(never)]
 #[no_mangle]
 fn random() -> [isize; 32] {
-    let r = unsafe { MaybeUninit::uninit().assume_init() };
+    let r = MaybeUninit::uninit();
     // Avoid optimizing everything out.
-    black_box(r)
+    unsafe { std::intrinsics::volatile_load(r.as_ptr()) }
 }
 
 #[inline(never)]
@@ -39,6 +42,6 @@ fn xor(a: &[isize]) -> isize {
 
 #[start]
 fn main(_: isize, _: *const *const u8) -> isize {
-    let r = random();
+    let r = black_box(random as fn() -> [isize; 32])();
     xor(&r)
 }