Define control flow instructions.

Rename 'br' to 'jump'. We'll use jump/br to mean unconditional/conditional
control transfer respectively.

cranelift/docs/cton_domain.py

@@ -262,7 +262,12 @@ class InstDocumenter(sphinx.ext.autodoc.Documenter):
         if len(inst.outs) > 0:
             sig = ', '.join([op.name for op in inst.outs]) + ' = ' + sig
         if len(inst.ins) > 0:
-            sig = sig + ' ' + ', '.join([op.name for op in inst.ins])
+            sig = sig + ' ' + inst.ins[0].name
+            for op in inst.ins[1:]:
+                if op.typ.operand_kind().name == 'variable_args':
+                    sig += '({}...)'.format(op.name)
+                else:
+                    sig += ', ' + op.name
         return sig
 
     def add_directive_header(self, sig):

cranelift/docs/langref.rst

@@ -313,56 +313,10 @@ arguments, if it has any. Conditional branches only take the branch if their
 condition is satisfied, otherwise execution continues at the following
 instruction in the EBB.
 
-.. inst:: br EBB(args...)
+.. autoinst:: jump
-
+.. autoinst:: brz
-    Branch.
+.. autoinst:: brnz
-
+.. autoinst:: br_table
-    Unconditionally branch to an extended basic block, passing the specified
-    EBB arguments. The number and types of arguments must match the destination
-    EBB.
-
-    :arg EBB: Destination extended basic block.
-    :arg args...: Zero or more arguments passed to EBB.
-    :result: None. This is a terminator instruction.
-
-.. inst:: brz x, EBB(args...)
-
-    Branch when zero.
-
-    If ``x`` is a :type:`b1` value, take the branch when ``x`` is false. If
-    ``x`` is an integer value, take the branch when ``x = 0``.
-
-    :arg Testable x: Value to test.
-    :arg EBB: Destination extended basic block.
-    :arg args...: Arguments passed to EBB.
-    :result: None.
-
-.. inst:: brnz x, EBB(args...)
-
-    Branch when non-zero.
-
-    If ``x`` is a :type:`b1` value, take the branch when ``x`` is true. If
-    ``x`` is an integer value, take the branch when ``x != 0``.
-
-    :arg Testable x: Value to test.
-    :arg EBB: Destination extended basic block.
-    :arg args...: Zero or more arguments passed to EBB.
-    :result: None.
-
-.. inst:: br_table x, JT
-
-    Jump table branch.
-
-    Use ``x`` as an unsigned index into the jump table ``JT``. If a jump table
-    entry is found, branch to the corresponding EBB. If no entry was found fall
-    through to the next instruction.
-
-    Note that this branch instruction can't pass arguments to the targeted
-    blocks. Split critical edges as needed to work around this.
-
-    :arg iN x: Integer index into jump table.
-    :arg JT: Jump table which was declared in the preamble.
-    :result: None.
 
 .. inst:: JT = jump_table EBB0, EBB1, ..., EBBn
 
@@ -386,29 +340,9 @@ explicit trap instructions defined below, but some instructions may also cause
 traps for certain input value. For example, :inst:`udiv` traps when the divisor
 is zero.
 
-.. inst:: trap
+.. autoinst:: trap
-
+.. autoinst:: trapz
-    Terminate execution unconditionally.
+.. autoinst:: trapnz
-
-    :result: None. This is a terminator instruction.
-
-.. inst:: trapz x
-
-    Trap when zero.
-
-    if ``x`` is non-zero, execution continues at the following instruction.
-
-    :arg Testable x: Value to test.
-    :result: None.
-
-.. inst:: trapnz x
-
-    Trap when non-zero.
-
-    if ``x`` is zero, execution continues at the following instruction.
-
-    :arg Testable x: Value to test.
-    :result: None.
 
 
 Function calls

cranelift/src/libcretonne/entities.rs

@@ -189,3 +189,34 @@ impl Default for StackSlot {
         NO_STACK_SLOT
     }
 }
+
+/// An opaque reference to a jump table.
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub struct JumpTable(u32);
+
+impl JumpTable {
+    pub fn new(index: usize) -> JumpTable {
+        assert!(index < (u32::MAX as usize));
+        JumpTable(index as u32)
+    }
+
+    pub fn index(&self) -> usize {
+        self.0 as usize
+    }
+}
+
+/// Display a `JumpTable` reference as "jt12".
+impl Display for JumpTable {
+    fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
+        write!(fmt, "jt{}", self.0)
+    }
+}
+
+/// A guaranteed invalid jump table reference.
+pub const NO_JUMP_TABLE: JumpTable = JumpTable(u32::MAX);
+
+impl Default for JumpTable {
+    fn default() -> JumpTable {
+        NO_JUMP_TABLE
+    }
+}

cranelift/src/libcretonne/instructions.rs

@@ -140,6 +140,22 @@ pub enum InstructionData {
         rhs: Value,
         lhs: Imm64,
     },
+    Jump {
+        opcode: Opcode,
+        ty: Type,
+        data: Box<JumpData>,
+    },
+    Branch {
+        opcode: Opcode,
+        ty: Type,
+        data: Box<BranchData>,
+    },
+    BranchTable {
+        opcode: Opcode,
+        ty: Type,
+        arg: Value,
+        table: JumpTable,
+    },
     Call {
         opcode: Opcode,
         ty: Type,
@@ -147,6 +163,66 @@ pub enum InstructionData {
     },
 }
 
+/// A variable list of `Value` operands used for function call arguments and passing arguments to
+/// basic blocks.
+#[derive(Debug)]
+pub struct VariableArgs(Vec<Value>);
+
+impl VariableArgs {
+    pub fn new() -> VariableArgs {
+        VariableArgs(Vec::new())
+    }
+}
+
+impl Display for VariableArgs {
+    fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
+        try!(write!(fmt, "("));
+        for (i, val) in self.0.iter().enumerate() {
+            if i == 0 {
+                try!(write!(fmt, "{}", val));
+            } else {
+                try!(write!(fmt, ", {}", val));
+            }
+        }
+        write!(fmt, ")")
+    }
+}
+
+impl Default for VariableArgs {
+    fn default() -> VariableArgs {
+        VariableArgs::new()
+    }
+}
+
+/// Payload data for jump instructions. These need to carry lists of EBB arguments that won't fit
+/// in the allowed InstructionData size.
+#[derive(Debug)]
+pub struct JumpData {
+    destination: Ebb,
+    arguments: VariableArgs,
+}
+
+impl Display for JumpData {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "{}{}", self.destination, self.arguments)
+    }
+}
+
+/// Payload data for branch instructions. These need to carry lists of EBB arguments that won't fit
+/// in the allowed InstructionData size.
+#[derive(Debug)]
+pub struct BranchData {
+    arg: Value,
+    destination: Ebb,
+    arguments: VariableArgs,
+}
+
+impl Display for BranchData {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "{}, {}{}", self.arg, self.destination, self.arguments)
+    }
+}
+
 /// Payload of a call instruction.
 #[derive(Debug)]
 pub struct CallData {
@@ -154,9 +230,14 @@ pub struct CallData {
     second_result: Value,
 
     // Dynamically sized array containing call argument values.
-    arguments: Vec<Value>,
+    arguments: VariableArgs,
 }
 
+impl Display for CallData {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "TBD{}", self.arguments)
+    }
+}
 
 impl InstructionData {
     /// Create data for a call instruction.
@@ -166,7 +247,7 @@ impl InstructionData {
             ty: return_type,
             data: Box::new(CallData {
                 second_result: NO_VALUE,
-                arguments: Vec::new(),
+                arguments: VariableArgs::new(),
             }),
         }
     }
@@ -184,6 +265,9 @@ impl InstructionData {
             Binary { opcode, .. } => opcode,
             BinaryImm { opcode, .. } => opcode,
             BinaryImmRev { opcode, .. } => opcode,
+            Jump { opcode, .. } => opcode,
+            Branch { opcode, .. } => opcode,
+            BranchTable { opcode, .. } => opcode,
             Call { opcode, .. } => opcode,
         }
     }
@@ -201,6 +285,9 @@ impl InstructionData {
             Binary { ty, .. } => ty,
             BinaryImm { ty, .. } => ty,
             BinaryImmRev { ty, .. } => ty,
+            Jump { ty, .. } => ty,
+            Branch { ty, .. } => ty,
+            BranchTable { ty, .. } => ty,
             Call { ty, .. } => ty,
         }
     }
@@ -218,6 +305,9 @@ impl InstructionData {
             Binary { .. } => None,
             BinaryImm { .. } => None,
             BinaryImmRev { .. } => None,
+            Jump { .. } => None,
+            Branch { .. } => None,
+            BranchTable { .. } => None,
             Call { ref data, .. } => Some(data.second_result),
         }
     }
@@ -234,6 +324,9 @@ impl InstructionData {
             Binary { .. } => None,
             BinaryImm { .. } => None,
             BinaryImmRev { .. } => None,
+            Jump { .. } => None,
+            Branch { .. } => None,
+            BranchTable { .. } => None,
             Call { ref mut data, .. } => Some(&mut data.second_result),
         }
     }
@@ -263,4 +356,15 @@ mod tests {
         assert_eq!("".parse::<Opcode>(), Err("Unknown opcode"));
         assert_eq!("\0".parse::<Opcode>(), Err("Unknown opcode"));
     }
+
+    #[test]
+    fn instruction_data() {
+        use std::mem;
+        // The size of the InstructionData enum is important for performance. It should not exceed
+        // 16 bytes. Use `Box<FooData>` out-of-line payloads for instruction formats that require
+        // more space than that.
+        // It would be fine with a data structure smaller than 16 bytes, but what are the odds of
+        // that?
+        assert_eq!(mem::size_of::<InstructionData>(), 16);
+    }
 }

cranelift/src/libcretonne/write.rs

@@ -155,7 +155,10 @@ pub fn write_instruction(w: &mut Write, func: &Function, inst: Inst) -> Result {
         Binary { opcode, args, .. } => writeln!(w, "{} {}, {}", opcode, args[0], args[1]),
         BinaryImm { opcode, lhs, rhs, .. } => writeln!(w, "{} {}, {}", opcode, lhs, rhs),
         BinaryImmRev { opcode, lhs, rhs, .. } => writeln!(w, "{} {}, {}", opcode, lhs, rhs),
-        Call { opcode, .. } => writeln!(w, "{} [...]", opcode),
+        Jump { opcode, ref data, .. } => writeln!(w, "{} {}", opcode, data),
+        Branch { opcode, ref data, .. } => writeln!(w, "{} {}", opcode, data),
+        BranchTable { opcode, arg, table, .. } => writeln!(w, "{} {}, {}", opcode, arg, table),
+        Call { opcode, ref data, .. } => writeln!(w, "{} {}", opcode, data),
     }
 }
 

cranelift/src/libreader/parser.rs

@@ -657,6 +657,9 @@ impl<'a> Parser<'a> {
                     rhs: rhs,
                 }
             }
+            InstructionFormat::Jump |
+            InstructionFormat::Branch |
+            InstructionFormat::BranchTable |
             InstructionFormat::Call => {
                 unimplemented!();
             }

meta/cretonne/__init__.py

@@ -450,6 +450,8 @@ class Instruction(object):
                 operands and other operand kinds.
     :param outs: Tuple of output operands. The output operands must be SSA
                 values.
+    :param is_terminator: This is a terminator instruction.
+    :param is_branch: This is a branch instruction.
     """
 
     def __init__(self, name, doc, ins=(), outs=(), **kwargs):

meta/cretonne/base.py

@@ -4,18 +4,94 @@ Cretonne base instruction set.
 This module defines the basic Cretonne instruction set that all targets
 support.
 """
-from . import TypeVar, Operand, Instruction, InstructionGroup
+from . import TypeVar, Operand, Instruction, InstructionGroup, variable_args
 from types import i8, f32, f64
 from immediates import imm64, ieee32, ieee64, immvector
+import entities
 
 instructions = InstructionGroup("base", "Shared base instruction set")
 
 Int = TypeVar('Int', 'A scalar or vector integer type', ints=True, simd=True)
 iB = TypeVar('iB', 'A scalar integer type', ints=True)
+Testable = TypeVar(
+        'Testable', 'A scalar boolean or integer type',
+        ints=True, bools=True)
 TxN = TypeVar(
         '%Tx%N', 'A SIMD vector type',
         ints=True, floats=True, bools=True, scalars=False, simd=True)
 
+#
+# Control flow
+#
+c = Operand('c', Testable, doc='Controlling value to test')
+EBB = Operand('EBB', entities.ebb, doc='Destination extended basic block')
+args = Operand('args', variable_args, doc='EBB arguments')
+
+jump = Instruction(
+        'jump', r"""
+        Jump.
+
+        Unconditionally jump to an extended basic block, passing the specified
+        EBB arguments. The number and types of arguments must match the
+        destination EBB.
+        """,
+        ins=(EBB, args), is_terminator=True)
+
+brz = Instruction(
+        'brz', r"""
+        Branch when zero.
+
+        If ``c`` is a :type:`b1` value, take the branch when ``c`` is false. If
+        ``c`` is an integer value, take the branch when ``c = 0``.
+        """,
+        ins=(c, EBB, args), is_branch=True)
+
+brnz = Instruction(
+        'brnz', r"""
+        Branch when non-zero.
+
+        If ``c`` is a :type:`b1` value, take the branch when ``c`` is true. If
+        ``c`` is an integer value, take the branch when ``c != 0``.
+        """,
+        ins=(c, EBB, args), is_branch=True)
+
+x = Operand('x', iB, doc='index into jump table')
+JT = Operand('JT', entities.jump_table)
+br_table = Instruction(
+        'br_table', r"""
+        Indirect branch via jump table.
+
+        Use ``x`` as an unsigned index into the jump table ``JT``. If a jump table
+        entry is found, branch to the corresponding EBB. If no entry was found fall
+        through to the next instruction.
+
+        Note that this branch instruction can't pass arguments to the targeted
+        blocks. Split critical edges as needed to work around this.
+        """,
+        ins=(x, JT), is_branch=True)
+
+trap = Instruction(
+        'trap', r"""
+        Terminate execution unconditionally.
+        """,
+        is_terminator=True)
+
+trapz = Instruction(
+        'trapz', r"""
+        Trap when zero.
+
+        if ``c`` is non-zero, execution continues at the following instruction.
+        """,
+        ins=c)
+
+trapnz = Instruction(
+        'trapnz', r"""
+        Trap when non-zero.
+
+        if ``c`` is zero, execution continues at the following instruction.
+        """,
+        ins=c)
+
 #
 # Materializing constants.
 #

meta/cretonne/entities.py

@@ -21,3 +21,6 @@ signature = EntityRefKind('signature', 'A function signature.')
 #: A reference to an external function declared in the function preamble.
 #: This is used to provide the callee and signature in a call instruction.
 function = EntityRefKind('function', 'An external function.')
+
+#: A reference to a jump table declared in the function preamble.
+jump_table = EntityRefKind('jump_table', 'A jump table.')

meta/cretonne/formats.py

@@ -9,7 +9,7 @@ in this module.
 
 from . import InstructionFormat, value, variable_args
 from immediates import imm64, ieee32, ieee64, immvector
-from entities import function
+from entities import ebb, function, jump_table
 
 Nullary = InstructionFormat()
 
@@ -23,6 +23,10 @@ Binary = InstructionFormat(value, value)
 BinaryImm = InstructionFormat(value, imm64)
 BinaryImmRev = InstructionFormat(imm64, value)
 
+Jump = InstructionFormat(ebb, variable_args)
+Branch = InstructionFormat(value, ebb, variable_args)
+BranchTable = InstructionFormat(value, jump_table)
+
 Call = InstructionFormat(function, variable_args, multiple_results=True)
 
 # Finally extract the names of global variables in this module.