Add well-known names for runtime library functions.

Add a LibCall type which represents runtime library functions that many
be synthesized by Cretonne from pure instructions.

Add a LibCall variant to ExternalName to represent one of these runtime
functions.

lib/cretonne/src/ir/extname.rs

@@ -4,7 +4,10 @@
 //! function. The name of an external declaration doesn't have any meaning to
 //! Cretonne, which compiles functions independently.
 
+use ir::LibCall;
+use std::cmp;
 use std::fmt::{self, Write};
+use std::str::FromStr;
 
 const TESTCASE_NAME_LENGTH: usize = 16;
 
@@ -23,19 +26,21 @@ pub enum ExternalName {
     /// A name in a user-defined symbol table. Cretonne does not interpret
     /// these numbers in any way.
     User {
-        /// Arbitrary
+        /// Arbitrary.
         namespace: u32,
-        /// Arbitrary
+        /// Arbitrary.
         index: u32,
     },
     /// A test case function name of up to 10 ascii characters. This is
     /// not intended to be used outside test cases.
     TestCase {
-        /// How many of the bytes in `ascii` are valid
+        /// How many of the bytes in `ascii` are valid?
         length: u8,
-        /// Ascii bytes of the name
+        /// Ascii bytes of the name.
         ascii: [u8; TESTCASE_NAME_LENGTH],
     },
+    /// A well-known runtime library function.
+    LibCall(LibCall),
 }
 
 impl ExternalName {
@@ -50,20 +55,12 @@ impl ExternalName {
     /// let name = ExternalName::testcase("hello");
     /// assert_eq!(name.to_string(), "%hello");
     /// ```
-    pub fn testcase<T>(v: T) -> ExternalName
-    where
-        T: Into<Vec<u8>>,
-    {
-        let vec = v.into();
-        let len = if vec.len() > TESTCASE_NAME_LENGTH {
-            TESTCASE_NAME_LENGTH
-        } else {
-            vec.len()
-        };
+    pub fn testcase<T: AsRef<[u8]>>(v: T) -> ExternalName {
+        let vec = v.as_ref();
+        let len = cmp::min(vec.len(), TESTCASE_NAME_LENGTH);
         let mut bytes = [0u8; TESTCASE_NAME_LENGTH];
-        for (i, &byte) in vec.iter().take(len).enumerate() {
-            bytes[i] = byte;
-        }
+        bytes[0..len].copy_from_slice(&vec[0..len]);
+
         ExternalName::TestCase {
             length: len as u8,
             ascii: bytes,
@@ -104,6 +101,19 @@ impl fmt::Display for ExternalName {
                 }
                 Ok(())
             }
+            ExternalName::LibCall(lc) => write!(f, "%{}", lc),
+        }
+    }
+}
+
+impl FromStr for ExternalName {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        // Try to parse as a libcall name, otherwise it's a test case.
+        match s.parse() {
+            Ok(lc) => Ok(ExternalName::LibCall(lc)),
+            Err(_) => Ok(ExternalName::testcase(s.as_bytes())),
         }
     }
 }
@@ -111,6 +121,7 @@ impl fmt::Display for ExternalName {
 #[cfg(test)]
 mod tests {
     use super::ExternalName;
+    use ir::LibCall;
 
     #[test]
     fn display_testcase() {
@@ -137,4 +148,16 @@ mod tests {
             "u4294967295:4294967295"
         );
     }
+
+    #[test]
+    fn parsing() {
+        assert_eq!(
+            "FloorF32".parse(),
+            Ok(ExternalName::LibCall(LibCall::FloorF32))
+        );
+        assert_eq!(
+            ExternalName::LibCall(LibCall::FloorF32).to_string(),
+            "%FloorF32"
+        );
+    }
 }

lib/cretonne/src/ir/libcall.rs

@@ -0,0 +1,114 @@
+//! Naming well-known routines in the runtime library.
+
+use ir::{types, Opcode, Type};
+use std::fmt;
+use std::str::FromStr;
+
+/// The name of a runtime library routine.
+///
+/// Runtime library calls are generated for Cretonne IL instructions that don't have an equivalent
+/// ISA instruction or an easy macro expansion. A `LibCall` is used as a well-known name to refer to
+/// the runtime library routine. This way, Cretonne doesn't have to know about the naming
+/// convention in the embedding VM's runtime library.
+///
+/// This list is likely to grow over time.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum LibCall {
+    /// ceil.f32
+    CeilF32,
+    /// ceil.f64
+    CeilF64,
+    /// floor.f32
+    FloorF32,
+    /// floor.f64
+    FloorF64,
+    /// trunc.f32
+    TruncF32,
+    /// frunc.f64
+    TruncF64,
+    /// nearest.f32
+    NearestF32,
+    /// nearest.f64
+    NearestF64,
+}
+
+const NAME: [&str; 8] = [
+    "CeilF32",
+    "CeilF64",
+    "FloorF32",
+    "FloorF64",
+    "TruncF32",
+    "TruncF64",
+    "NearestF32",
+    "NearestF64",
+];
+
+impl fmt::Display for LibCall {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str(NAME[*self as usize])
+    }
+}
+
+impl FromStr for LibCall {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "CeilF32" => Ok(LibCall::CeilF32),
+            "CeilF64" => Ok(LibCall::CeilF64),
+            "FloorF32" => Ok(LibCall::FloorF32),
+            "FloorF64" => Ok(LibCall::FloorF64),
+            "TruncF32" => Ok(LibCall::TruncF32),
+            "TruncF64" => Ok(LibCall::TruncF64),
+            "NearestF32" => Ok(LibCall::NearestF32),
+            "NearestF64" => Ok(LibCall::NearestF64),
+            _ => Err(()),
+        }
+    }
+}
+
+impl LibCall {
+    /// Get the well-known library call name to use as a replacement for an instruction with the
+    /// given opcode and controlling type variable.
+    ///
+    /// Returns `None` if no well-known library routine name exists for that instruction.
+    pub fn for_inst(opcode: Opcode, ctrl_type: Type) -> Option<LibCall> {
+        Some(match ctrl_type {
+            types::F32 => {
+                match opcode {
+                    Opcode::Ceil => LibCall::CeilF32,
+                    Opcode::Floor => LibCall::FloorF32,
+                    Opcode::Trunc => LibCall::TruncF32,
+                    Opcode::Nearest => LibCall::NearestF32,
+                    _ => return None,
+                }
+            }
+            types::F64 => {
+                match opcode {
+                    Opcode::Ceil => LibCall::CeilF64,
+                    Opcode::Floor => LibCall::FloorF64,
+                    Opcode::Trunc => LibCall::TruncF64,
+                    Opcode::Nearest => LibCall::NearestF64,
+                    _ => return None,
+                }
+            }
+            _ => return None,
+        })
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn display() {
+        assert_eq!(LibCall::CeilF32.to_string(), "CeilF32");
+        assert_eq!(LibCall::NearestF64.to_string(), "NearestF64");
+    }
+
+    #[test]
+    fn parsing() {
+        assert_eq!("FloorF32".parse(), Ok(LibCall::FloorF32));
+    }
+}

lib/cretonne/src/ir/mod.rs

@@ -15,6 +15,7 @@ mod extfunc;
 mod extname;
 mod globalvar;
 mod heap;
+mod libcall;
 mod memflags;
 mod progpoint;
 mod sourceloc;
@@ -33,6 +34,7 @@ pub use ir::heap::{HeapData, HeapStyle, HeapBase};
 pub use ir::instructions::{Opcode, InstructionData, VariableArgs, ValueList, ValueListPool};
 pub use ir::jumptable::JumpTableData;
 pub use ir::layout::Layout;
+pub use ir::libcall::LibCall;
 pub use ir::memflags::MemFlags;
 pub use ir::progpoint::{ProgramPoint, ProgramOrder, ExpandedProgramPoint};
 pub use ir::sourceloc::SourceLoc;

lib/reader/src/parser.rs

@@ -885,7 +885,9 @@ impl<'a> Parser<'a> {
         match self.token() {
             Some(Token::Name(s)) => {
                 self.consume();
-                Ok(ExternalName::testcase(s))
+                s.parse().map_err(
+                    |_| self.error("invalid test case or libcall name"),
+                )
             }
             Some(Token::UserRef(namespace)) => {
                 self.consume();