Require target features to match exactly during inlining

In general it is not correct to inline a callee with a target features
that are subset of the callee. Require target features to match exactly
during inlining.

The exact match could be potentially relaxed, but this would require
identifying specific feature that are allowed to differ, those that need
to match, and those that can be present in caller but not in callee.

This resolves MIR part of #116573. For other concerns with respect to
the previous implementation also see areInlineCompatible in LLVM.

2 files changed, 3 insertions, 5 deletions

diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index 8b33e00c63c..277060573bc 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -438,10 +438,8 @@ impl<'tcx> Inliner<'tcx> {
             return Err("incompatible instruction set");
         }
 
-        for feature in &callee_attrs.target_features {
-            if !self.codegen_fn_attrs.target_features.contains(feature) {
-                return Err("incompatible target feature");
-            }
+        if callee_attrs.target_features != self.codegen_fn_attrs.target_features {
+            return Err("incompatible target features");
         }
 
         Ok(())
diff --git a/tests/mir-opt/inline/inline_compatibility.rs b/tests/mir-opt/inline/inline_compatibility.rs
index 8045ea39f95..3ad880715fe 100644
--- a/tests/mir-opt/inline/inline_compatibility.rs
+++ b/tests/mir-opt/inline/inline_compatibility.rs
@@ -31,7 +31,7 @@ pub unsafe fn f1() {
 
 // CHECK-LABEL: fn f2()
 // CHECK:       bb0: {
-// CHECK-NEXT:  return;
+// CHECK-NEXT:  nop()
 #[target_feature(enable = "avx")]
 pub unsafe fn f2() {
     nop();