Prevent miscompilation in trivial loop {}

Ideally, we would want to handle a broader set of cases to fully fix the
underlying bug here. That is currently relatively expensive at compile and
runtime, so we don't do that for now.

1 files changed, 5 insertions, 5 deletions

diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index e76e86f5651..368aba6eae0 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -334,8 +334,8 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
         self.call(expect, &[cond, self.const_bool(expected)], None)
     }
 
-    fn sideeffect(&mut self) {
-        if self.tcx.sess.opts.debugging_opts.insert_sideeffect {
+    fn sideeffect(&mut self, unconditional: bool) {
+        if unconditional || self.tcx.sess.opts.debugging_opts.insert_sideeffect {
             let fnname = self.get_intrinsic(&("llvm.sideeffect"));
             self.call(fnname, &[], None);
         }
@@ -390,7 +390,7 @@ fn codegen_msvc_try(
 ) {
     let llfn = get_rust_try_fn(bx, &mut |mut bx| {
         bx.set_personality_fn(bx.eh_personality());
-        bx.sideeffect();
+        bx.sideeffect(false);
 
         let mut normal = bx.build_sibling_block("normal");
         let mut catchswitch = bx.build_sibling_block("catchswitch");
@@ -553,7 +553,7 @@ fn codegen_gnu_try(
         //      call %catch_func(%data, %ptr)
         //      ret 1
 
-        bx.sideeffect();
+        bx.sideeffect(false);
 
         let mut then = bx.build_sibling_block("then");
         let mut catch = bx.build_sibling_block("catch");
@@ -615,7 +615,7 @@ fn codegen_emcc_try(
         //      call %catch_func(%data, %catch_data)
         //      ret 1
 
-        bx.sideeffect();
+        bx.sideeffect(false);
 
         let mut then = bx.build_sibling_block("then");
         let mut catch = bx.build_sibling_block("catch");