Change opt-level from 2 back to 3

In Cargo.toml, the opt-level for `release` and `bench` was
overridden to be 2. This was to work around a problem with LLVM
7. However, rust no longer uses LLVM 7, so this is no longer
needed.

This creates a small compile time regression in MIR constant eval,
so I've added a #[inline(always)] on the `step` function used in
const eval

Also creates a binary size increase in wasm-stringify-ints-small,
so I've bumped the limit there.

Cargo.toml

@@ -30,13 +30,6 @@ exclude = [
   "obj",
 ]
 
-# Curiously, LLVM 7.0 will segfault if compiled with opt-level=3
-# See issue https://github.com/rust-lang/rust/issues/52378
-[profile.release]
-opt-level = 2
-[profile.bench]
-opt-level = 2
-
 # These options are controlled from our rustc wrapper script, so turn them off
 # here and have them controlled elsewhere.
 [profile.dev]

src/librustc_mir/interpret/step.rs

@@ -38,6 +38,9 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     /// Returns `true` as long as there are more things to do.
     ///
     /// This is used by [priroda](https://github.com/oli-obk/priroda)
+    ///
+    /// This is marked `#inline(always)` to work around adverserial codegen when `opt-level = 3`
+    #[inline(always)]
     pub fn step(&mut self) -> InterpResult<'tcx, bool> {
         if self.stack.is_empty() {
             return Ok(false);

src/test/run-make/wasm-stringify-ints-small/Makefile

@@ -4,7 +4,7 @@ ifeq ($(TARGET),wasm32-unknown-unknown)
 all:
 	$(RUSTC) foo.rs -C lto -O --target wasm32-unknown-unknown
 	wc -c < $(TMPDIR)/foo.wasm
-	[ "`wc -c < $(TMPDIR)/foo.wasm`" -lt "20500" ]
+	[ "`wc -c < $(TMPDIR)/foo.wasm`" -lt "25000" ]
 else
 all:
 endif