From 772460ea7f0c54937d808dd6991facaaa93aaec9 Mon Sep 17 00:00:00 2001
From: coolreader18 <33094578+coolreader18@users.noreply.github.com>
Date: Sun, 4 Aug 2019 01:22:51 -0500
Subject: [PATCH] Add tuple unpacking optimization

---
 bytecode/src/bytecode.rs |  4 +++
 compiler/src/peephole.rs | 58 ++++++++++++++++++++++++++--------------
 vm/src/frame.rs          | 20 +++++++-------
 3 files changed, 52 insertions(+), 30 deletions(-)

diff --git a/bytecode/src/bytecode.rs b/bytecode/src/bytecode.rs
index 40da926f4..0d5008b83 100644
--- a/bytecode/src/bytecode.rs
+++ b/bytecode/src/bytecode.rs
@@ -219,6 +219,9 @@ pub enum Instruction {
         spec: String,
     },
     PopException,
+    Reverse {
+        amount: usize,
+    },
 }
 
 use self::Instruction::*;
@@ -438,6 +441,7 @@ impl Instruction {
             Unpack => w!(Unpack),
             FormatValue { spec, .. } => w!(FormatValue, spec), // TODO: write conversion
             PopException => w!(PopException),
+            Reverse { amount } => w!(Reverse, amount),
         }
     }
 }
diff --git a/compiler/src/peephole.rs b/compiler/src/peephole.rs
index adfd71e1f..c0bc5a0b4 100644
--- a/compiler/src/peephole.rs
+++ b/compiler/src/peephole.rs
@@ -10,8 +10,8 @@ struct InstructionMetadata {
     labels: Vec<Label>,
 }
 
-impl InstructionMetadata {
-    fn from_multiple(metas: Vec<Self>) -> Self {
+impl From<Vec<InstructionMetadata>> for InstructionMetadata {
+    fn from(metas: Vec<Self>) -> Self {
         debug_assert!(!metas.is_empty(), "`metas` must not be empty");
         InstructionMetadata {
             loc: metas[0].loc.clone(),
@@ -69,28 +69,28 @@ impl<O: OutputStream> PeepholeOptimizer<O> {
     }
 
     fn optimize(&mut self, instruction: Instruction, meta: InstructionMetadata) {
+        macro_rules! lc {
+            ($name:ident {$($field:tt)*}) => {
+                Instruction::LoadConst {
+                    value: bytecode::Constant::$name {$($field)*},
+                }
+            };
+            ($name:ident, $($value:tt)*) => {
+                lc!($name { value: $($value)* })
+            };
+        }
+        macro_rules! emitconst {
+            ([$($metas:expr),*], $($arg:tt)*) => {
+                self.emit(
+                    lc!($($arg)*),
+                    InstructionMetadata::from(vec![$($metas),*]),
+                )
+            };
+        }
         match instruction {
             Instruction::BinaryOperation { op, inplace } => {
                 let (rhs, rhs_meta) = self.pop();
                 let (lhs, lhs_meta) = self.pop();
-                macro_rules! lc {
-                    ($name:ident {$($field:tt)*}) => {
-                        Instruction::LoadConst {
-                            value: bytecode::Constant::$name {$($field)*},
-                        }
-                    };
-                    ($name:ident, $($value:tt)*) => {
-                        lc!($name { value: $($value)* })
-                    };
-                }
-                macro_rules! emitconst {
-                    ([$($metas:expr),*], $($arg:tt)*) => {
-                        self.emit(
-                            lc!($($arg)*),
-                            InstructionMetadata::from_multiple(vec![$($metas),*]),
-                        )
-                    };
-                }
                 macro_rules! op {
                     ($op:ident) => {
                         bytecode::BinaryOperator::$op
@@ -129,6 +129,24 @@ impl<O: OutputStream> PeepholeOptimizer<O> {
                     }
                 }
             }
+            Instruction::UnpackSequence { size } => {
+                let (arg, arg_meta) = self.pop();
+                match arg {
+                    Instruction::BuildTuple {
+                        size: tup_size,
+                        unpack,
+                    } if !unpack && tup_size == size => {
+                        self.emit(
+                            Instruction::Reverse { amount: size },
+                            vec![arg_meta, meta].into(),
+                        );
+                    }
+                    arg => {
+                        self.emit(arg, arg_meta);
+                        self.emit(instruction, meta);
+                    }
+                }
+            }
             other => self.emit(other, meta),
         }
     }
diff --git a/vm/src/frame.rs b/vm/src/frame.rs
index b70cb658c..82879f8a6 100644
--- a/vm/src/frame.rs
+++ b/vm/src/frame.rs
@@ -662,6 +662,12 @@ impl Frame {
                     panic!("Block type must be ExceptHandler here.")
                 }
             }
+            bytecode::Instruction::Reverse { amount } => {
+                let mut stack = self.stack.borrow_mut();
+                let stack_len = stack.len();
+                stack[stack_len - amount..stack_len].reverse();
+                Ok(None)
+            }
         }
     }
 
@@ -676,10 +682,7 @@ impl Frame {
         if unpack {
             let mut result: Vec<PyObjectRef> = vec![];
             for element in elements {
-                let expanded = vm.extract_elements(&element)?;
-                for inner in expanded {
-                    result.push(inner);
-                }
+                result.extend(vm.extract_elements(&element)?);
             }
             Ok(result)
         } else {
@@ -1170,12 +1173,9 @@ impl Frame {
     }
 
     fn pop_multiple(&self, count: usize) -> Vec<PyObjectRef> {
-        let mut objs: Vec<PyObjectRef> = Vec::new();
-        for _x in 0..count {
-            objs.push(self.pop_value());
-        }
-        objs.reverse();
-        objs
+        let mut stack = self.stack.borrow_mut();
+        let stack_len = stack.len();
+        stack.drain(stack_len - count..stack_len).collect()
     }
 
     fn last_value(&self) -> PyObjectRef {