rustc_codegen_ssa: append blocks to functions w/o creating a builder.

Author: eddyb

compiler/rustc_codegen_llvm/src/builder.rs

@@ -118,24 +118,16 @@ macro_rules! builder_methods_for_value_instructions {
 }
 
 impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
-    fn new_block<'b>(cx: &'a CodegenCx<'ll, 'tcx>, llfn: &'ll Value, name: &'b str) -> Self {
-        let mut bx = Builder::with_cx(cx);
-        let llbb = unsafe {
-            let name = SmallCStr::new(name);
-            llvm::LLVMAppendBasicBlockInContext(cx.llcx, llfn, name.as_ptr())
-        };
-        bx.position_at_end(llbb);
+    fn build(cx: &'a CodegenCx<'ll, 'tcx>, llbb: &'ll BasicBlock) -> Self {
+        let bx = Builder::with_cx(cx);
+        unsafe {
+            llvm::LLVMPositionBuilderAtEnd(bx.llbuilder, llbb);
+        }
         bx
     }
 
-    fn with_cx(cx: &'a CodegenCx<'ll, 'tcx>) -> Self {
-        // Create a fresh builder from the crate context.
-        let llbuilder = unsafe { llvm::LLVMCreateBuilderInContext(cx.llcx) };
-        Builder { llbuilder, cx }
-    }
-
-    fn build_sibling_block(&self, name: &str) -> Self {
-        Builder::new_block(self.cx, self.llfn(), name)
+    fn cx(&self) -> &CodegenCx<'ll, 'tcx> {
+        self.cx
     }
 
     fn llbb(&self) -> &'ll BasicBlock {
@@ -144,12 +136,22 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
 
     fn set_span(&mut self, _span: Span) {}
 
-    fn position_at_end(&mut self, llbb: &'ll BasicBlock) {
+    fn append_block(cx: &'a CodegenCx<'ll, 'tcx>, llfn: &'ll Value, name: &str) -> &'ll BasicBlock {
         unsafe {
-            llvm::LLVMPositionBuilderAtEnd(self.llbuilder, llbb);
+            let name = SmallCStr::new(name);
+            llvm::LLVMAppendBasicBlockInContext(cx.llcx, llfn, name.as_ptr())
         }
     }
 
+    fn append_sibling_block(&mut self, name: &str) -> &'ll BasicBlock {
+        Self::append_block(self.cx, self.llfn(), name)
+    }
+
+    fn build_sibling_block(&mut self, name: &str) -> Self {
+        let llbb = self.append_sibling_block(name);
+        Self::build(self.cx, llbb)
+    }
+
     fn ret_void(&mut self) {
         unsafe {
             llvm::LLVMBuildRetVoid(self.llbuilder);
@@ -1144,10 +1146,6 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         unsafe { llvm::LLVMBuildZExt(self.llbuilder, val, dest_ty, UNNAMED) }
     }
 
-    fn cx(&self) -> &CodegenCx<'ll, 'tcx> {
-        self.cx
-    }
-
     fn do_not_inline(&mut self, llret: &'ll Value) {
         llvm::Attribute::NoInline.apply_callsite(llvm::AttributePlace::Function, llret);
     }
@@ -1161,6 +1159,12 @@ impl StaticBuilderMethods for Builder<'a, 'll, 'tcx> {
 }
 
 impl Builder<'a, 'll, 'tcx> {
+    fn with_cx(cx: &'a CodegenCx<'ll, 'tcx>) -> Self {
+        // Create a fresh builder from the crate context.
+        let llbuilder = unsafe { llvm::LLVMCreateBuilderInContext(cx.llcx) };
+        Builder { llbuilder, cx }
+    }
+
     pub fn llfn(&self) -> &'ll Value {
         unsafe { llvm::LLVMGetBasicBlockParent(self.llbb()) }
     }

compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs

@@ -223,7 +223,8 @@ fn declare_unused_fn(cx: &CodegenCx<'ll, 'tcx>, def_id: &DefId) -> Instance<'tcx
 
 fn codegen_unused_fn_and_counter(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'tcx>) {
     let llfn = cx.get_fn(instance);
-    let mut bx = Builder::new_block(cx, llfn, "unused_function");
+    let llbb = Builder::append_block(cx, llfn, "unused_function");
+    let mut bx = Builder::build(cx, llbb);
     let fn_name = bx.get_pgo_func_name_var(instance);
     let hash = bx.const_u64(0);
     let num_counters = bx.const_u32(1);

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -678,7 +678,8 @@ fn gen_fn<'ll, 'tcx>(
     cx.apply_target_cpu_attr(llfn);
     // FIXME(eddyb) find a nicer way to do this.
     unsafe { llvm::LLVMRustSetLinkage(llfn, llvm::Linkage::InternalLinkage) };
-    let bx = Builder::new_block(cx, llfn, "entry-block");
+    let llbb = Builder::append_block(cx, llfn, "entry-block");
+    let bx = Builder::build(cx, llbb);
     codegen(bx);
     llfn
 }

compiler/rustc_codegen_ssa/src/base.rs

@@ -409,7 +409,8 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         cx.set_frame_pointer_elimination(llfn);
         cx.apply_target_cpu_attr(llfn);
 
-        let mut bx = Bx::new_block(&cx, llfn, "top");
+        let llbb = Bx::append_block(&cx, llfn, "top");
+        let mut bx = Bx::build(&cx, llbb);
 
         bx.insert_reference_to_gdb_debug_scripts_section_global();
 

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -386,7 +386,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
         // Create the failure block and the conditional branch to it.
         let lltarget = helper.llblock(self, target);
-        let panic_block = self.new_block("panic");
+        let panic_block = bx.build_sibling_block("panic");
         if expected {
             bx.cond_br(cond, lltarget, panic_block.llbb());
         } else {
@@ -1289,8 +1289,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         })
     }
 
-    pub fn new_block(&self, name: &str) -> Bx {
-        Bx::new_block(self.cx, self.llfn, name)
+    // FIXME(eddyb) replace with `build_sibling_block`/`append_sibling_block`
+    // (which requires having a `Bx` already, and not all callers do).
+    fn new_block(&self, name: &str) -> Bx {
+        let llbb = Bx::append_block(self.cx, self.llfn, name);
+        Bx::build(self.cx, llbb)
     }
 
     /// Get the backend `BasicBlock` for a MIR `BasicBlock`, either already
@@ -1300,17 +1303,15 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     pub fn llbb(&mut self, bb: mir::BasicBlock) -> Bx::BasicBlock {
         self.cached_llbbs[bb].unwrap_or_else(|| {
             // FIXME(eddyb) only name the block if `fewer_names` is `false`.
-            // FIXME(eddyb) create the block directly, without a builder.
-            let llbb = self.new_block(&format!("{:?}", bb)).llbb();
+            let llbb = Bx::append_block(self.cx, self.llfn, &format!("{:?}", bb));
             self.cached_llbbs[bb] = Some(llbb);
             llbb
         })
     }
 
     pub fn build_block(&mut self, bb: mir::BasicBlock) -> Bx {
-        let mut bx = Bx::with_cx(self.cx);
-        bx.position_at_end(self.llbb(bb));
-        bx
+        let llbb = self.llbb(bb);
+        Bx::build(self.cx, llbb)
     }
 
     fn make_return_dest(

compiler/rustc_codegen_ssa/src/mir/mod.rs

@@ -144,7 +144,8 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 
     let debug_context = cx.create_function_debug_context(instance, &fn_abi, llfn, &mir);
 
-    let mut bx = Bx::new_block(cx, llfn, "start");
+    let start_llbb = Bx::append_block(cx, llfn, "start");
+    let mut bx = Bx::build(cx, start_llbb);
 
     if mir.basic_blocks().iter().any(|bb| bb.is_cleanup) {
         bx.set_personality_fn(cx.eh_personality());
@@ -159,7 +160,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
             .indices()
             .map(|bb| {
                 if bb == mir::START_BLOCK && !reentrant_start_block {
-                    Some(bx.llbb())
+                    Some(start_llbb)
                 } else {
                     None
                 }

compiler/rustc_codegen_ssa/src/traits/builder.rs

@@ -40,14 +40,21 @@ pub trait BuilderMethods<'a, 'tcx>:
     + HasParamEnv<'tcx>
     + HasTargetSpec
 {
-    fn new_block<'b>(cx: &'a Self::CodegenCx, llfn: Self::Function, name: &'b str) -> Self;
-    fn with_cx(cx: &'a Self::CodegenCx) -> Self;
-    fn build_sibling_block(&self, name: &str) -> Self;
+    fn build(cx: &'a Self::CodegenCx, llbb: Self::BasicBlock) -> Self;
+
     fn cx(&self) -> &Self::CodegenCx;
     fn llbb(&self) -> Self::BasicBlock;
+
     fn set_span(&mut self, span: Span);
 
-    fn position_at_end(&mut self, llbb: Self::BasicBlock);
+    // FIXME(eddyb) replace uses of this with `append_sibling_block`.
+    fn append_block(cx: &'a Self::CodegenCx, llfn: Self::Function, name: &str) -> Self::BasicBlock;
+
+    fn append_sibling_block(&mut self, name: &str) -> Self::BasicBlock;
+
+    // FIXME(eddyb) replace with callers using `append_sibling_block`.
+    fn build_sibling_block(&mut self, name: &str) -> Self;
+
     fn ret_void(&mut self);
     fn ret(&mut self, v: Self::Value);
     fn br(&mut self, dest: Self::BasicBlock);