Auto merge of rust-lang#123256 - saethlin:instsimplify-earlier, r=<try>

Run InstSimplify before UnreachablePropagation

This is the pass ordering change I was musing about: rust-lang#122975 (comment)

r? `@ghost`

Author: bors

compiler/rustc_mir_transform/src/instsimplify.rs

@@ -11,42 +11,59 @@ use rustc_span::symbol::Symbol;
 use rustc_target::abi::FieldIdx;
 use rustc_target::spec::abi::Abi;
 
-pub struct InstSimplify;
+pub enum InstSimplify {
+    BeforeUnreachablePropagation,
+    Final,
+}
 
 impl<'tcx> MirPass<'tcx> for InstSimplify {
+    fn name(&self) -> &'static str {
+        match &self {
+            InstSimplify::BeforeUnreachablePropagation => {
+                "InstSimplify-before-unreachable-propagation"
+            }
+            InstSimplify::Final => "InstSimplify-final",
+        }
+    }
+
     fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
         sess.mir_opt_level() > 0
     }
 
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-        let ctx = InstSimplifyContext {
-            tcx,
-            local_decls: &body.local_decls,
-            param_env: tcx.param_env_reveal_all_normalized(body.source.def_id()),
-        };
-        let preserve_ub_checks =
-            attr::contains_name(tcx.hir().krate_attrs(), sym::rustc_preserve_ub_checks);
-        for block in body.basic_blocks.as_mut() {
-            for statement in block.statements.iter_mut() {
-                match statement.kind {
-                    StatementKind::Assign(box (_place, ref mut rvalue)) => {
-                        if !preserve_ub_checks {
-                            ctx.simplify_ub_check(&statement.source_info, rvalue);
-                        }
-                        ctx.simplify_bool_cmp(&statement.source_info, rvalue);
-                        ctx.simplify_ref_deref(&statement.source_info, rvalue);
-                        ctx.simplify_len(&statement.source_info, rvalue);
-                        ctx.simplify_cast(rvalue);
+        inst_simplify(tcx, body);
+    }
+}
+
+fn inst_simplify<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
+    let ctx = InstSimplifyContext {
+        tcx,
+        local_decls: &body.local_decls,
+        param_env: tcx.param_env_reveal_all_normalized(body.source.def_id()),
+    };
+    let preserve_ub_checks =
+        attr::contains_name(tcx.hir().krate_attrs(), sym::rustc_preserve_ub_checks);
+    for block in body.basic_blocks.as_mut() {
+        for statement in block.statements.iter_mut() {
+            match statement.kind {
+                StatementKind::Assign(box (_place, ref mut rvalue)) => {
+                    if !preserve_ub_checks {
+                        ctx.simplify_ub_check(&statement.source_info, rvalue);
                     }
-                    _ => {}
+                    ctx.simplify_bool_cmp(&statement.source_info, rvalue);
+                    ctx.simplify_ref_deref(&statement.source_info, rvalue);
+                    ctx.simplify_len(&statement.source_info, rvalue);
+                    ctx.simplify_cast(rvalue);
                 }
+                _ => {}
             }
-
-            ctx.simplify_primitive_clone(block.terminator.as_mut().unwrap(), &mut block.statements);
-            ctx.simplify_intrinsic_assert(block.terminator.as_mut().unwrap());
-            ctx.simplify_nounwind_call(block.terminator.as_mut().unwrap());
-            simplify_duplicate_switch_targets(block.terminator.as_mut().unwrap());
         }
+
+        let terminator = block.terminator.as_mut().unwrap();
+        ctx.simplify_primitive_clone(terminator, &mut block.statements);
+        ctx.simplify_intrinsic_assert(terminator);
+        ctx.simplify_nounwind_call(terminator);
+        simplify_duplicate_switch_targets(terminator);
     }
 }
 

compiler/rustc_mir_transform/src/lib.rs

@@ -581,6 +581,7 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
             &remove_unneeded_drops::RemoveUnneededDrops,
             // Type instantiation may create uninhabited enums.
             &uninhabited_enum_branching::UninhabitedEnumBranching,
+            &instsimplify::InstSimplify::BeforeUnreachablePropagation,
             &unreachable_prop::UnreachablePropagation,
             &o1(simplify::SimplifyCfg::AfterUninhabitedEnumBranching),
             // Inlining may have introduced a lot of redundant code and a large move pattern.
@@ -591,9 +592,9 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
             &ref_prop::ReferencePropagation,
             &sroa::ScalarReplacementOfAggregates,
             &match_branches::MatchBranchSimplification,
-            // inst combine is after MatchBranchSimplification to clean up Ne(_1, false)
+            // InstSimplify is after MatchBranchSimplification to clean up Ne(_1, false)
             &multiple_return_terminators::MultipleReturnTerminators,
-            &instsimplify::InstSimplify,
+            &instsimplify::InstSimplify::Final,
             &simplify::SimplifyLocals::BeforeConstProp,
             &dead_store_elimination::DeadStoreElimination::Initial,
             &gvn::GVN,

tests/mir-opt/const_prop/slice_len.rs

@@ -1,5 +1,5 @@
 //@ unit-test: GVN
-//@ compile-flags: -Zmir-enable-passes=+InstSimplify
+//@ compile-flags: -Zmir-enable-passes=+InstSimplify-before-unreachable-propagation
 // EMIT_MIR_FOR_EACH_PANIC_STRATEGY
 // EMIT_MIR_FOR_EACH_BIT_WIDTH
 

tests/mir-opt/dataflow-const-prop/slice_len.rs

@@ -1,6 +1,6 @@
 // EMIT_MIR_FOR_EACH_PANIC_STRATEGY
 //@ unit-test: DataflowConstProp
-//@ compile-flags: -Zmir-enable-passes=+InstSimplify
+//@ compile-flags: -Zmir-enable-passes=+InstSimplify-before-unreachable-propagation
 // EMIT_MIR_FOR_EACH_BIT_WIDTH
 
 // EMIT_MIR slice_len.main.DataflowConstProp.diff

tests/mir-opt/instsimplify/bool_compare.eq_false.InstSimplify.diff renamed to tests/mir-opt/instsimplify/bool_compare.eq_false.InstSimplify-before-unreachable-propagation.diff

@@ -1,5 +1,5 @@
-- // MIR for `eq_false` before InstSimplify
-+ // MIR for `eq_false` after InstSimplify
+- // MIR for `eq_false` before InstSimplify-before-unreachable-propagation
++ // MIR for `eq_false` after InstSimplify-before-unreachable-propagation
 
   fn eq_false(_1: bool) -> u32 {
       debug x => _1;

tests/mir-opt/instsimplify/bool_compare.eq_true.InstSimplify.diff renamed to tests/mir-opt/instsimplify/bool_compare.eq_true.InstSimplify-before-unreachable-propagation.diff

@@ -1,5 +1,5 @@
-- // MIR for `eq_true` before InstSimplify
-+ // MIR for `eq_true` after InstSimplify
+- // MIR for `eq_true` before InstSimplify-before-unreachable-propagation
++ // MIR for `eq_true` after InstSimplify-before-unreachable-propagation
 
   fn eq_true(_1: bool) -> u32 {
       debug x => _1;

tests/mir-opt/instsimplify/bool_compare.false_eq.InstSimplify.diff renamed to tests/mir-opt/instsimplify/bool_compare.false_eq.InstSimplify-before-unreachable-propagation.diff

@@ -1,5 +1,5 @@
-- // MIR for `false_eq` before InstSimplify
-+ // MIR for `false_eq` after InstSimplify
+- // MIR for `false_eq` before InstSimplify-before-unreachable-propagation
++ // MIR for `false_eq` after InstSimplify-before-unreachable-propagation
 
   fn false_eq(_1: bool) -> u32 {
       debug x => _1;

tests/mir-opt/instsimplify/bool_compare.false_ne.InstSimplify.diff renamed to tests/mir-opt/instsimplify/bool_compare.false_ne.InstSimplify-before-unreachable-propagation.diff

@@ -1,5 +1,5 @@
-- // MIR for `false_ne` before InstSimplify
-+ // MIR for `false_ne` after InstSimplify
+- // MIR for `false_ne` before InstSimplify-before-unreachable-propagation
++ // MIR for `false_ne` after InstSimplify-before-unreachable-propagation
 
   fn false_ne(_1: bool) -> u32 {
       debug x => _1;

tests/mir-opt/instsimplify/bool_compare.ne_false.InstSimplify.diff renamed to tests/mir-opt/instsimplify/bool_compare.ne_false.InstSimplify-before-unreachable-propagation.diff

@@ -1,5 +1,5 @@
-- // MIR for `ne_false` before InstSimplify
-+ // MIR for `ne_false` after InstSimplify
+- // MIR for `ne_false` before InstSimplify-before-unreachable-propagation
++ // MIR for `ne_false` after InstSimplify-before-unreachable-propagation
 
   fn ne_false(_1: bool) -> u32 {
       debug x => _1;

tests/mir-opt/instsimplify/bool_compare.ne_true.InstSimplify.diff renamed to tests/mir-opt/instsimplify/bool_compare.ne_true.InstSimplify-before-unreachable-propagation.diff

@@ -1,5 +1,5 @@
-- // MIR for `ne_true` before InstSimplify
-+ // MIR for `ne_true` after InstSimplify
+- // MIR for `ne_true` before InstSimplify-before-unreachable-propagation
++ // MIR for `ne_true` after InstSimplify-before-unreachable-propagation
 
   fn ne_true(_1: bool) -> u32 {
       debug x => _1;