Drop 'basic-blocks' feature (#1363)

* All: Drop 'basic-blocks' feature

This makes it so that 'basic-blocks' cannot be disabled and we can
start assuming it everywhere.

* Tests: Replace non-bb filetests with bb version

* Tests: Adapt solver-fixedconflict filetests to use basic blocks

cranelift/frontend/Cargo.toml

@@ -18,13 +18,10 @@ hashbrown = { version = "0.6", optional = true }
 smallvec = { version = "1.0.0" }
 
 [features]
-default = ["std", "basic-blocks"]
+default = ["std"]
 std = ["cranelift-codegen/std"]
 core = ["hashbrown", "cranelift-codegen/core"]
 
-# Temporary feature that enforces basic block semantics.
-basic-blocks = ["cranelift-codegen/basic-blocks"]
-
 [badges]
 maintenance = { status = "experimental" }
 travis-ci = { repository = "bytecodealliance/cranelift" }

cranelift/frontend/src/frontend.rs

@@ -480,7 +480,6 @@ impl<'a> FunctionBuilder<'a> {
         );
 
         // In debug mode, check that all blocks are valid basic blocks.
-        #[cfg(feature = "basic-blocks")]
         #[cfg(debug_assertions)]
         {
             // Iterate manually to provide more helpful error messages.