From 950437a035aa81cf2af3d8aebdf8d9b294c54395 Mon Sep 17 00:00:00 2001 From: Ben Kimock Date: Wed, 28 Aug 2024 19:36:46 -0400 Subject: [PATCH] Use a reduced recursion limit in the MIR inliner's cycle breaker --- compiler/rustc_mir_transform/src/inline/cycle.rs | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/compiler/rustc_mir_transform/src/inline/cycle.rs b/compiler/rustc_mir_transform/src/inline/cycle.rs index 56e8905bead3c..c65cc993b19fd 100644 --- a/compiler/rustc_mir_transform/src/inline/cycle.rs +++ b/compiler/rustc_mir_transform/src/inline/cycle.rs @@ -135,6 +135,14 @@ pub(crate) fn mir_callgraph_reachable<'tcx>( } false } + // FIXME(-Znext-solver): Remove this hack when trait solver overflow can return an error. + // In code like that pointed out in #128887, the type complexity we ask the solver to deal with + // grows as we recurse into the call graph. If we use the same recursion limit here and in the + // solver, the solver hits the limit first and emits a fatal error. But if we use a reduced + // limit, we will hit the limit first and give up on looking for inlining. And in any case, + // the default recursion limits are quite generous for us. If we need to recurse 64 times + // into the call graph, we're probably not going to find any useful MIR inlining. + let recursion_limit = tcx.recursion_limit() / 2; process( tcx, param_env, @@ -143,7 +151,7 @@ pub(crate) fn mir_callgraph_reachable<'tcx>( &mut Vec::new(), &mut FxHashSet::default(), &mut FxHashMap::default(), - tcx.recursion_limit(), + recursion_limit, ) }