feat(avm)!: variants for SET opcode (#8441)

Saves approx 5-10% bytecode size*

This one is not expected to save a lot of space because it already unofficially had variants (however the addresses are getting smaller now). This PR also
* Allows SET_FF with size field
* Therefore removes extra Brillig codegen necessary to handle big fields
* Makes serde of SET opcodes uniform (does not need special casing)
* Avoids extra casting in the transpiler, making set opcodes 1-1 with Brillig (no pc adjustment needed)

*don't believe the benchmark run, that one is against master and takes into account the whole PR stack.

Author: fcarreiro

avm-transpiler/src/instructions.rs

@@ -1,6 +1,8 @@
 use std::fmt::{self, Display};
 use std::fmt::{Debug, Formatter};
 
+use acvm::{AcirField, FieldElement};
+
 use crate::opcodes::AvmOpcode;
 
 /// Common values of the indirect instruction flag
@@ -110,6 +112,7 @@ pub enum AvmOperand {
     U32 { value: u32 },
     U64 { value: u64 },
     U128 { value: u128 },
+    FF { value: FieldElement },
 }
 
 impl Display for AvmOperand {
@@ -120,6 +123,7 @@ impl Display for AvmOperand {
             AvmOperand::U32 { value } => write!(f, " U32:{}", value),
             AvmOperand::U64 { value } => write!(f, " U64:{}", value),
             AvmOperand::U128 { value } => write!(f, " U128:{}", value),
+            AvmOperand::FF { value } => write!(f, " FF:{}", value),
         }
     }
 }
@@ -132,6 +136,7 @@ impl AvmOperand {
             AvmOperand::U32 { value } => value.to_be_bytes().to_vec(),
             AvmOperand::U64 { value } => value.to_be_bytes().to_vec(),
             AvmOperand::U128 { value } => value.to_be_bytes().to_vec(),
+            AvmOperand::FF { value } => value.to_be_bytes(),
         }
     }
 }

avm-transpiler/src/opcodes.rs

@@ -41,7 +41,12 @@ pub enum AvmOpcode {
     INTERNALCALL,
     INTERNALRETURN,
     // Memory
-    SET,
+    SET_8,
+    SET_16,
+    SET_32,
+    SET_64,
+    SET_128,
+    SET_FF,
     MOV_8,
     MOV_16,
     CMOV,
@@ -129,7 +134,12 @@ impl AvmOpcode {
             AvmOpcode::INTERNALCALL => "INTERNALCALL",
             AvmOpcode::INTERNALRETURN => "INTERNALRETURN",
             // Machine State - Memory
-            AvmOpcode::SET => "SET",
+            AvmOpcode::SET_8 => "SET_8",
+            AvmOpcode::SET_16 => "SET_16",
+            AvmOpcode::SET_32 => "SET_32",
+            AvmOpcode::SET_64 => "SET_64",
+            AvmOpcode::SET_128 => "SET_128",
+            AvmOpcode::SET_FF => "SET_FF",
             AvmOpcode::MOV_8 => "MOV_8",
             AvmOpcode::MOV_16 => "MOV_16",
             AvmOpcode::CMOV => "CMOV",

avm-transpiler/src/transpile.rs

@@ -6,7 +6,7 @@ use acvm::acir::circuit::BrilligOpcodeLocation;
 use acvm::brillig_vm::brillig::{
     BinaryFieldOp, BinaryIntOp, BlackBoxOp, HeapArray, HeapVector, MemoryAddress, ValueOrArray,
 };
-use acvm::{AcirField, FieldElement};
+use acvm::FieldElement;
 use noirc_errors::debug_info::DebugInfo;
 
 use crate::bit_traits::bits_needed_for;
@@ -674,45 +674,38 @@ fn handle_const(
 ) {
     let tag = tag_from_bit_size(*bit_size);
     let dest = destination.to_usize() as u32;
-
-    if !matches!(tag, AvmTypeTag::FIELD) {
-        avm_instrs.push(generate_set_instruction(tag, dest, value.to_u128(), indirect));
-    } else {
-        // We can't fit a field in an instruction. This should've been handled in Brillig.
-        let field = value;
-        if field.num_bits() > 128 {
-            panic!("SET: Field value doesn't fit in 128 bits, that's not supported!");
-        }
-        avm_instrs.extend([
-            generate_set_instruction(AvmTypeTag::UINT128, dest, field.to_u128(), indirect),
-            generate_cast_instruction(dest, indirect, dest, indirect, AvmTypeTag::FIELD),
-        ]);
-    }
+    avm_instrs.push(generate_set_instruction(tag, dest, value, indirect));
 }
 
 /// Generates an AVM SET instruction.
 fn generate_set_instruction(
     tag: AvmTypeTag,
     dest: u32,
-    value: u128,
+    value: &FieldElement,
     indirect: bool,
 ) -> AvmInstruction {
+    let bits_needed_val = bits_needed_for(value);
+    let bits_needed_mem = if bits_needed_val >= 16 { 16 } else { bits_needed_for(&dest) };
+    assert!(bits_needed_mem <= 16);
+    let bits_needed_opcode = bits_needed_val.max(bits_needed_mem);
+
+    let set_opcode = match bits_needed_opcode {
+        8 => AvmOpcode::SET_8,
+        16 => AvmOpcode::SET_16,
+        32 => AvmOpcode::SET_32,
+        64 => AvmOpcode::SET_64,
+        128 => AvmOpcode::SET_128,
+        254 => AvmOpcode::SET_FF,
+        _ => panic!("Invalid bits needed for opcode: {}", bits_needed_opcode),
+    };
+
     AvmInstruction {
-        opcode: AvmOpcode::SET,
+        opcode: set_opcode,
         indirect: if indirect { Some(ZEROTH_OPERAND_INDIRECT) } else { Some(ALL_DIRECT) },
         tag: Some(tag),
         operands: vec![
-            // const
-            match tag {
-                AvmTypeTag::UINT8 => AvmOperand::U8 { value: value as u8 },
-                AvmTypeTag::UINT16 => AvmOperand::U16 { value: value as u16 },
-                AvmTypeTag::UINT32 => AvmOperand::U32 { value: value as u32 },
-                AvmTypeTag::UINT64 => AvmOperand::U64 { value: value as u64 },
-                AvmTypeTag::UINT128 => AvmOperand::U128 { value },
-                _ => panic!("Invalid type tag {:?} for set", tag),
-            },
-            // dest offset
-            AvmOperand::U32 { value: dest },
+            make_operand(bits_needed_opcode, value),
+            make_operand(bits_needed_mem, &dest),
         ],
     }
 }
@@ -1137,8 +1130,6 @@ pub fn map_brillig_pcs_to_avm_pcs(brillig_bytecode: &[BrilligOpcode<FieldElement
     pc_map[0] = 0; // first PC is always 0 as there are no instructions inserted by AVM at start
     for i in 0..brillig_bytecode.len() - 1 {
         let num_avm_instrs_for_this_brillig_instr = match &brillig_bytecode[i] {
-            BrilligOpcode::Const { bit_size: BitSize::Field, .. } => 2,
-            BrilligOpcode::IndirectConst { bit_size: BitSize::Field, .. } => 2,
             BrilligOpcode::Cast { bit_size: BitSize::Integer(IntegerBitSize::U1), .. } => 3,
             _ => 1,
         };

avm-transpiler/src/utils.rs

@@ -1,7 +1,7 @@
 use fxhash::FxHashMap as HashMap;
 
 use acvm::acir::circuit::brillig::BrilligFunctionId;
-use acvm::FieldElement;
+use acvm::{AcirField, FieldElement};
 use log::{debug, info, trace};
 
 use acvm::acir::brillig::Opcode as BrilligOpcode;
@@ -91,13 +91,15 @@ pub fn dbg_print_avm_program(avm_program: &[AvmInstruction]) {
     }
 }
 
-pub fn make_operand<T: Into<u128> + Copy>(bits: usize, value: &T) -> AvmOperand {
+pub fn make_operand<T: Into<FieldElement> + Clone>(bits: usize, value: &T) -> AvmOperand {
+    let field: FieldElement = value.clone().into();
     match bits {
-        8 => AvmOperand::U8 { value: Into::<u128>::into(*value) as u8 },
-        16 => AvmOperand::U16 { value: Into::<u128>::into(*value) as u16 },
-        32 => AvmOperand::U32 { value: Into::<u128>::into(*value) as u32 },
-        64 => AvmOperand::U64 { value: Into::<u128>::into(*value) as u64 },
-        128 => AvmOperand::U128 { value: Into::<u128>::into(*value) },
+        8 => AvmOperand::U8 { value: field.try_to_u32().unwrap() as u8 },
+        16 => AvmOperand::U16 { value: field.try_to_u32().unwrap() as u16 },
+        32 => AvmOperand::U32 { value: field.try_to_u32().unwrap() },
+        64 => AvmOperand::U64 { value: field.try_to_u64().unwrap() },
+        128 => AvmOperand::U128 { value: field.try_into_u128().unwrap() },
+        254 => AvmOperand::FF { value: field },
         _ => panic!("Invalid operand size for bits: {}", bits),
     }
 }