From 9d23c8617632690326ac04e25646ac669179de4b Mon Sep 17 00:00:00 2001 From: Camille GILLOT Date: Wed, 26 Jun 2024 12:16:40 +0000 Subject: [PATCH] Reduce allocations in GVN. --- compiler/rustc_mir_transform/src/gvn.rs | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs index 8eab9890d63..c290ad6fa2c 100644 --- a/compiler/rustc_mir_transform/src/gvn.rs +++ b/compiler/rustc_mir_transform/src/gvn.rs @@ -128,7 +128,7 @@ fn propagate_ssa<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { // Clone dominators as we need them while mutating the body. let dominators = body.basic_blocks.dominators().clone(); - let mut state = VnState::new(tcx, param_env, &ssa, &dominators, &body.local_decls); + let mut state = VnState::new(tcx, body, param_env, &ssa, &dominators, &body.local_decls); ssa.for_each_assignment_mut( body.basic_blocks.as_mut_preserves_cfg(), |local, value, location| { @@ -266,20 +266,28 @@ struct VnState<'body, 'tcx> { impl<'body, 'tcx> VnState<'body, 'tcx> { fn new( tcx: TyCtxt<'tcx>, + body: &Body<'tcx>, param_env: ty::ParamEnv<'tcx>, ssa: &'body SsaLocals, dominators: &'body Dominators, local_decls: &'body LocalDecls<'tcx>, ) -> Self { + // Compute a rough estimate of the number of values in the body from the number of + // statements. This is meant to reduce the number of allocations, but it's all right if + // we miss the exact amount. We estimate based on 2 values per statement (one in LHS and + // one in RHS) and 4 values per terminator (for call operands). + let num_values = + 2 * body.basic_blocks.iter().map(|bbdata| bbdata.statements.len()).sum::() + + 4 * body.basic_blocks.len(); VnState { tcx, ecx: InterpCx::new(tcx, DUMMY_SP, param_env, DummyMachine), param_env, local_decls, locals: IndexVec::from_elem(None, local_decls), - rev_locals: IndexVec::default(), - values: FxIndexSet::default(), - evaluated: IndexVec::new(), + rev_locals: IndexVec::with_capacity(num_values), + values: FxIndexSet::with_capacity_and_hasher(num_values, Default::default()), + evaluated: IndexVec::with_capacity(num_values), next_opaque: Some(0), feature_unsized_locals: tcx.features().unsized_locals, ssa,