Implement asm goto for LLVM and GCC backend

5 files changed, 84 insertions, 22 deletions

diff --git a/compiler/rustc_codegen_gcc/src/asm.rs b/compiler/rustc_codegen_gcc/src/asm.rs
index 78e8e32b972..07edd26e27a 100644
--- a/compiler/rustc_codegen_gcc/src/asm.rs
+++ b/compiler/rustc_codegen_gcc/src/asm.rs
@@ -107,7 +107,7 @@ enum ConstraintOrRegister {
 
 
 impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
-    fn codegen_inline_asm(&mut self, template: &[InlineAsmTemplatePiece], rust_operands: &[InlineAsmOperandRef<'tcx, Self>], options: InlineAsmOptions, span: &[Span], instance: Instance<'_>, _dest_catch_funclet: Option<(Self::BasicBlock, Self::BasicBlock, Option<&Self::Funclet>)>) {
+    fn codegen_inline_asm(&mut self, template: &[InlineAsmTemplatePiece], rust_operands: &[InlineAsmOperandRef<'tcx, Self>], options: InlineAsmOptions, span: &[Span], instance: Instance<'_>, dest: Option<Self::BasicBlock>, _catch_funclet: Option<(Self::BasicBlock, Option<&Self::Funclet>)>) {
         if options.contains(InlineAsmOptions::MAY_UNWIND) {
             self.sess().dcx()
                 .create_err(UnwindingInlineAsm { span: span[0] })
@@ -126,6 +126,10 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
         // added to `outputs.len()`
         let mut inputs = vec![];
 
+        // GCC index of a label equals its position in the array added to
+        // `outputs.len() + inputs.len()`.
+        let mut labels = vec![];
+
         // Clobbers collected from `out("explicit register") _` and `inout("expl_reg") var => _`
         let mut clobbers = vec![];
 
@@ -269,6 +273,10 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
                     // some targets to add a leading underscore (Mach-O).
                     constants_len += self.tcx.symbol_name(Instance::mono(self.tcx, def_id)).name.len();
                 }
+
+                InlineAsmOperandRef::Label { label } => {
+                    labels.push(label);
+                }
             }
         }
 
@@ -368,6 +376,10 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
                 InlineAsmOperandRef::Const { .. } => {
                     // processed in the previous pass
                 }
+
+                InlineAsmOperandRef::Label { .. } => {
+                    // processed in the previous pass
+                }
             }
         }
 
@@ -454,6 +466,14 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
                         InlineAsmOperandRef::Const { ref string } => {
                             template_str.push_str(string);
                         }
+
+                        InlineAsmOperandRef::Label { label } => {
+                            let label_gcc_index = labels.iter()
+                                .position(|&l| l == label)
+                                .expect("wrong rust index");
+                            let gcc_index = label_gcc_index + outputs.len() + inputs.len();
+                            push_to_template(Some('l'), gcc_index);
+                        }
                     }
                 }
             }
@@ -466,7 +486,12 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
         // 4. Generate Extended Asm block
 
         let block = self.llbb();
-        let extended_asm = block.add_extended_asm(None, &template_str);
+        let extended_asm = if let Some(dest) = dest {
+            assert!(!labels.is_empty());
+            block.end_with_extended_asm_goto(None, &template_str, &labels, Some(dest))
+        } else {
+            block.add_extended_asm(None, &template_str)
+        };
 
         for op in &outputs {
             extended_asm.add_output_operand(None, &op.to_constraint(), op.tmp_var);
@@ -494,7 +519,7 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
         if !options.contains(InlineAsmOptions::NOSTACK) {
             // TODO(@Commeownist): figure out how to align stack
         }
-        if options.contains(InlineAsmOptions::NORETURN) {
+        if dest.is_none() && options.contains(InlineAsmOptions::NORETURN) {
             let builtin_unreachable = self.context.get_builtin_function("__builtin_unreachable");
             let builtin_unreachable: RValue<'gcc> = unsafe { std::mem::transmute(builtin_unreachable) };
             self.call(self.type_void(), None, None, builtin_unreachable, &[], None);
diff --git a/compiler/rustc_codegen_llvm/src/asm.rs b/compiler/rustc_codegen_llvm/src/asm.rs
index a413466093b..f5d0b3c4657 100644
--- a/compiler/rustc_codegen_llvm/src/asm.rs
+++ b/compiler/rustc_codegen_llvm/src/asm.rs
@@ -28,7 +28,8 @@ impl<'ll, 'tcx> AsmBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
         options: InlineAsmOptions,
         line_spans: &[Span],
         instance: Instance<'_>,
-        dest_catch_funclet: Option<(Self::BasicBlock, Self::BasicBlock, Option<&Self::Funclet>)>,
+        dest: Option<Self::BasicBlock>,
+        catch_funclet: Option<(Self::BasicBlock, Option<&Self::Funclet>)>,
     ) {
         let asm_arch = self.tcx.sess.asm_arch.unwrap();
 
@@ -165,6 +166,7 @@ impl<'ll, 'tcx> AsmBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
         }
 
         // Build the template string
+        let mut labels = vec![];
         let mut template_str = String::new();
         for piece in template {
             match *piece {
@@ -205,6 +207,11 @@ impl<'ll, 'tcx> AsmBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                             // Only emit the raw symbol name
                             template_str.push_str(&format!("${{{}:c}}", op_idx[&operand_idx]));
                         }
+                        InlineAsmOperandRef::Label { label } => {
+                            template_str.push_str(&format!("${{{}:l}}", constraints.len()));
+                            constraints.push("!i".to_owned());
+                            labels.push(label);
+                        }
                     }
                 }
             }
@@ -292,12 +299,14 @@ impl<'ll, 'tcx> AsmBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
             &constraints.join(","),
             &inputs,
             output_type,
+            &labels,
             volatile,
             alignstack,
             dialect,
             line_spans,
             options.contains(InlineAsmOptions::MAY_UNWIND),
-            dest_catch_funclet,
+            dest,
+            catch_funclet,
         )
         .unwrap_or_else(|| span_bug!(line_spans[0], "LLVM asm constraint validation failed"));
 
@@ -317,7 +326,7 @@ impl<'ll, 'tcx> AsmBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
         attributes::apply_to_callsite(result, llvm::AttributePlace::Function, &{ attrs });
 
         // Switch to the 'normal' basic block if we did an `invoke` instead of a `call`
-        if let Some((dest, _, _)) = dest_catch_funclet {
+        if let Some(dest) = dest {
             self.switch_to_block(dest);
         }
 
@@ -415,16 +424,14 @@ pub(crate) fn inline_asm_call<'ll>(
     cons: &str,
     inputs: &[&'ll Value],
     output: &'ll llvm::Type,
+    labels: &[&'ll llvm::BasicBlock],
     volatile: bool,
     alignstack: bool,
     dia: llvm::AsmDialect,
     line_spans: &[Span],
     unwind: bool,
-    dest_catch_funclet: Option<(
-        &'ll llvm::BasicBlock,
-        &'ll llvm::BasicBlock,
-        Option<&Funclet<'ll>>,
-    )>,
+    dest: Option<&'ll llvm::BasicBlock>,
+    catch_funclet: Option<(&'ll llvm::BasicBlock, Option<&Funclet<'ll>>)>,
 ) -> Option<&'ll Value> {
     let volatile = if volatile { llvm::True } else { llvm::False };
     let alignstack = if alignstack { llvm::True } else { llvm::False };
@@ -457,8 +464,10 @@ pub(crate) fn inline_asm_call<'ll>(
                 can_throw,
             );
 
-            let call = if let Some((dest, catch, funclet)) = dest_catch_funclet {
-                bx.invoke(fty, None, None, v, inputs, dest, catch, funclet)
+            let call = if !labels.is_empty() {
+                bx.callbr(fty, None, None, v, inputs, dest.unwrap(), labels, None)
+            } else if let Some((catch, funclet)) = catch_funclet {
+                bx.invoke(fty, None, None, v, inputs, dest.unwrap(), catch, funclet)
             } else {
                 bx.call(fty, None, None, v, inputs, None)
             };
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index 23e6f054a7c..ee76038800f 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -377,12 +377,14 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                     constraint,
                     inputs,
                     self.type_void(),
+                    &[],
                     true,
                     false,
                     llvm::AsmDialect::Att,
                     &[span],
                     false,
                     None,
+                    None,
                 )
                 .unwrap_or_else(|| bug!("failed to generate inline asm call for `black_box`"));
 
diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs
index c9a1e7789c2..2eba489cbfb 100644
--- a/compiler/rustc_codegen_ssa/src/mir/block.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/block.rs
@@ -264,7 +264,7 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
             mir::UnwindAction::Unreachable => None,
         };
 
-        if let Some(cleanup) = unwind_target {
+        if operands.iter().any(|x| matches!(x, InlineAsmOperandRef::Label { .. })) {
             let ret_llbb = if let Some(target) = destination {
                 fx.llbb(target)
             } else {
@@ -277,11 +277,29 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
                 options,
                 line_spans,
                 instance,
-                Some((ret_llbb, cleanup, self.funclet(fx))),
+                Some(ret_llbb),
+                None,
+            );
+            MergingSucc::False
+        } else if let Some(cleanup) = unwind_target {
+            let ret_llbb = if let Some(target) = destination {
+                fx.llbb(target)
+            } else {
+                fx.unreachable_block()
+            };
+
+            bx.codegen_inline_asm(
+                template,
+                operands,
+                options,
+                line_spans,
+                instance,
+                Some(ret_llbb),
+                Some((cleanup, self.funclet(fx))),
             );
             MergingSucc::False
         } else {
-            bx.codegen_inline_asm(template, operands, options, line_spans, instance, None);
+            bx.codegen_inline_asm(template, operands, options, line_spans, instance, None, None);
 
             if let Some(target) = destination {
                 self.funclet_br(fx, bx, target, mergeable_succ)
@@ -1067,7 +1085,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         operands: &[mir::InlineAsmOperand<'tcx>],
         options: ast::InlineAsmOptions,
         line_spans: &[Span],
-        destination: Option<mir::BasicBlock>,
+        targets: &[mir::BasicBlock],
         unwind: mir::UnwindAction,
         instance: Instance<'_>,
         mergeable_succ: bool,
@@ -1119,8 +1137,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 mir::InlineAsmOperand::SymStatic { def_id } => {
                     InlineAsmOperandRef::SymStatic { def_id }
                 }
-                mir::InlineAsmOperand::Label { target_index: _ } => {
-                    todo!();
+                mir::InlineAsmOperand::Label { target_index } => {
+                    InlineAsmOperandRef::Label { label: self.llbb(targets[target_index]) }
                 }
             })
             .collect();
@@ -1132,7 +1150,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             &operands,
             options,
             line_spans,
-            destination,
+            if options.contains(InlineAsmOptions::NORETURN) {
+                None
+            } else {
+                targets.get(0).copied()
+            },
             unwind,
             instance,
             mergeable_succ,
@@ -1298,7 +1320,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 operands,
                 options,
                 line_spans,
-                targets.get(0).copied(),
+                targets,
                 unwind,
                 self.instance,
                 mergeable_succ(),
diff --git a/compiler/rustc_codegen_ssa/src/traits/asm.rs b/compiler/rustc_codegen_ssa/src/traits/asm.rs
index c2ae74b18d8..8d67b626bbd 100644
--- a/compiler/rustc_codegen_ssa/src/traits/asm.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/asm.rs
@@ -33,6 +33,9 @@ pub enum InlineAsmOperandRef<'tcx, B: BackendTypes + ?Sized> {
     SymStatic {
         def_id: DefId,
     },
+    Label {
+        label: B::BasicBlock,
+    },
 }
 
 #[derive(Debug)]
@@ -51,7 +54,8 @@ pub trait AsmBuilderMethods<'tcx>: BackendTypes {
         options: InlineAsmOptions,
         line_spans: &[Span],
         instance: Instance<'_>,
-        dest_catch_funclet: Option<(Self::BasicBlock, Self::BasicBlock, Option<&Self::Funclet>)>,
+        dest: Option<Self::BasicBlock>,
+        catch_funclet: Option<(Self::BasicBlock, Option<&Self::Funclet>)>,
     );
 }