Auto merge of #145910 - saethlin:ignore-intrinsic-calls, r=cjgillot

Ignore intrinsic calls in cross-crate-inlining cost model

I noticed in a side project that a function which just compares to `[u64; 2]` for equality is not cross-crate-inlinable. That was surprising to me because I didn't think that code contained a function call, but of course our array comparisons are lowered to an intrinsic. Intrinsic calls don't make a function no longer a leaf, so it makes sense to add this as an exception to the "only leaves" cross-crate-inline heuristic.

This is the useful compare link: https://perf.rust-lang.org/compare.html?start=7cb1a81145a739c4fd858abe3c624ce8e6e5f9cd&end=c3f0a64dbf9fba4722dacf8e39d2fe00069c995e&stat=instructions%3Au because it disables CGU merging in both commits, so effects that cause changes in the sysroot to perturb partitioning downstream are excluded. Perturbations to what is and isn't cross-crate-inlinable in the sysroot has chaotic effects on what items are in which CGUs after merging. It looks like before this PR by sheer luck some of the CGUs dirtied by the patch in eza incr-unchanged happened to be merged together, and with this PR they are not.

The perf runs on this PR point to a nice runtime performance improvement.

3 files changed, 13 insertions, 0 deletions

diff --git a/tests/codegen-llvm/cross-crate-inlining/auxiliary/leaf.rs b/tests/codegen-llvm/cross-crate-inlining/auxiliary/leaf.rs
index d059a3d0a73..7b5679c3f4d 100644
--- a/tests/codegen-llvm/cross-crate-inlining/auxiliary/leaf.rs
+++ b/tests/codegen-llvm/cross-crate-inlining/auxiliary/leaf.rs
@@ -18,3 +18,8 @@ pub fn stem_fn() -> String {
 fn inner() -> String {
     String::from("test")
 }
+
+// This function's optimized MIR contains a call, but it is to an intrinsic.
+pub fn leaf_with_intrinsic(a: &[u64; 2], b: &[u64; 2]) -> bool {
+    a == b
+}
diff --git a/tests/codegen-llvm/cross-crate-inlining/leaf-inlining.rs b/tests/codegen-llvm/cross-crate-inlining/leaf-inlining.rs
index 37132312ca9..5e7912791ad 100644
--- a/tests/codegen-llvm/cross-crate-inlining/leaf-inlining.rs
+++ b/tests/codegen-llvm/cross-crate-inlining/leaf-inlining.rs
@@ -18,3 +18,10 @@ pub fn stem_outer() -> String {
     // CHECK: call {{.*}}stem_fn
     leaf::stem_fn()
 }
+
+// Check that we inline functions that call intrinsics
+#[no_mangle]
+pub fn leaf_with_intrinsic_outer(a: &[u64; 2], b: &[u64; 2]) -> bool {
+    // CHECK-NOT: call {{.*}}leaf_with_intrinsic
+    leaf::leaf_with_intrinsic(a, b)
+}
diff --git a/tests/codegen-llvm/default-visibility.rs b/tests/codegen-llvm/default-visibility.rs
index 88ff9fee254..28238e5ef12 100644
--- a/tests/codegen-llvm/default-visibility.rs
+++ b/tests/codegen-llvm/default-visibility.rs
@@ -32,6 +32,7 @@ pub static tested_symbol: [u8; 6] = *b"foobar";
 // INTERPOSABLE: @{{.*}}default_visibility{{.*}}tested_symbol{{.*}} = constant
 // DEFAULT:      @{{.*}}default_visibility{{.*}}tested_symbol{{.*}} = constant
 
+#[inline(never)]
 pub fn do_memcmp(left: &[u8], right: &[u8]) -> i32 {
     left.cmp(right) as i32
 }