From cfbf1bf7cd300ddbfd2826488469c0921738685a Mon Sep 17 00:00:00 2001
From: Gary Guo <gary@garyguo.net>
Date: Wed, 28 Jun 2023 15:16:11 +0100
Subject: [PATCH] Do not create new resume block if there isn't one already
---
.../src/remove_noop_landing_pads.rs | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/compiler/rustc_mir_transform/src/remove_noop_landing_pads.rs b/compiler/rustc_mir_transform/src/remove_noop_landing_pads.rs
index 4941c9edce3..4e85c76fbc0 100644
--- a/compiler/rustc_mir_transform/src/remove_noop_landing_pads.rs
+++ b/compiler/rustc_mir_transform/src/remove_noop_landing_pads.rs
@@ -6,8 +6,8 @@ use rustc_middle::ty::TyCtxt;
use rustc_target::spec::PanicStrategy;
/// A pass that removes noop landing pads and replaces jumps to them with
-/// `None`. This is important because otherwise LLVM generates terrible
-/// code for these.
+/// `UnwindAction::Continue`. This is important because otherwise LLVM generates
+/// terrible code for these.
pub struct RemoveNoopLandingPads;
impl<'tcx> MirPass<'tcx> for RemoveNoopLandingPads {
@@ -84,7 +84,17 @@ impl RemoveNoopLandingPads {
fn remove_nop_landing_pads(&self, body: &mut Body<'_>) {
debug!("body: {:#?}", body);
- // make sure there's a resume block
+ // Skip the pass if there are no blocks with a resume terminator.
+ let has_resume = body
+ .basic_blocks
+ .iter_enumerated()
+ .any(|(_bb, block)| matches!(block.terminator().kind, TerminatorKind::Resume));
+ if !has_resume {
+ debug!("remove_noop_landing_pads: no resume block in MIR");
+ return;
+ }
+
+ // make sure there's a resume block without any statements
let resume_block = {
let mut patch = MirPatch::new(body);
let resume_block = patch.resume_block();