chore(avm-transpiler): return u8 in comparison ops (#5280)

This makes sense and allows us to remove a Brillig hack. cc @sirasistant
AztecProtocol · Mar 18, 2024 · 1a5eb69 · 1a5eb69
1 parent 20d9c0c
commit 1a5eb69
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Showing 5 changed files with 17 additions and 34 deletions.
diff --git a/avm-transpiler/src/transpile.rs b/avm-transpiler/src/transpile.rs
@@ -61,10 +61,6 @@ pub fn brillig_to_avm(brillig: &Brillig) -> Vec<u8> {
                         },
                     ],
                 });
-                // Brillig currently expects comparison instructions to return an u1 (for us, an u8).
-                if avm_opcode == AvmOpcode::EQ {
-                    avm_instrs.push(generate_cast_instruction(destination.to_usize() as u32, destination.to_usize() as u32, AvmTypeTag::UINT8));
-                }
             }
             BrilligOpcode::BinaryIntOp {
                 destination,
@@ -107,10 +103,6 @@ pub fn brillig_to_avm(brillig: &Brillig) -> Vec<u8> {
                         },
                     ],
                 });
-                // Brillig currently expects comparison instructions to return an u1 (for us, an u8).
-                if avm_opcode == AvmOpcode::EQ || avm_opcode == AvmOpcode::LT || avm_opcode == AvmOpcode::LTE {
-                    avm_instrs.push(generate_cast_instruction(destination.to_usize() as u32, destination.to_usize() as u32, AvmTypeTag::UINT8));
-                }
             }
             BrilligOpcode::CalldataCopy { destination_address, size, offset } => {
                 avm_instrs.push(AvmInstruction {
@@ -998,15 +990,6 @@ fn map_brillig_pcs_to_avm_pcs(initial_offset: usize, brillig: &Brillig) -> Vec<u
     for i in 0..brillig.bytecode.len() - 1 {
         let num_avm_instrs_for_this_brillig_instr = match &brillig.bytecode[i] {
             BrilligOpcode::Const { bit_size: 254, .. } => 2,
-            // Brillig currently expects comparison instructions to return an u1 (for us, an u8).
-            BrilligOpcode::BinaryIntOp {
-                op: BinaryIntOp::Equals | BinaryIntOp::LessThan | BinaryIntOp::LessThanEquals,
-                ..
-            } => 2,
-            BrilligOpcode::BinaryFieldOp {
-                op: BinaryFieldOp::Equals,
-                ..
-            } => 2,
             _ => 1,
         };
         // next Brillig pc will map to an AVM pc offset by the

diff --git a/yarn-project/simulator/src/avm/opcodes/comparators.test.ts b/yarn-project/simulator/src/avm/opcodes/comparators.test.ts
@@ -1,5 +1,5 @@
 import { AvmContext } from '../avm_context.js';
-import { Field, TypeTag, Uint16, Uint32 } from '../avm_memory_types.js';
+import { Field, TypeTag, Uint8, Uint16, Uint32 } from '../avm_memory_types.js';
 import { TagCheckError } from '../errors.js';
 import { initContext } from '../fixtures/index.js';
 import { Eq, Lt, Lte } from './comparators.js';
@@ -43,7 +43,7 @@ describe('Comparators', () => {
       ].forEach(i => i.execute(context));
 
       const actual = context.machineState.memory.getSlice(/*offset=*/ 10, /*size=*/ 4);
-      expect(actual).toEqual([new Uint32(0), new Uint32(0), new Uint32(1)]);
+      expect(actual).toEqual([new Uint8(0), new Uint8(0), new Uint8(1)]);
     });
 
     it('Works on field elements', async () => {
@@ -56,7 +56,7 @@ describe('Comparators', () => {
       ].forEach(i => i.execute(context));
 
       const actual = context.machineState.memory.getSlice(/*offset=*/ 10, /*size=*/ 4);
-      expect(actual).toEqual([new Field(0), new Field(0), new Field(1)]);
+      expect(actual).toEqual([new Uint8(0), new Uint8(0), new Uint8(1)]);
     });
 
     it('InTag is checked', async () => {
@@ -107,7 +107,7 @@ describe('Comparators', () => {
       ].forEach(i => i.execute(context));
 
       const actual = context.machineState.memory.getSlice(/*offset=*/ 10, /*size=*/ 4);
-      expect(actual).toEqual([new Uint32(0), new Uint32(1), new Uint32(0)]);
+      expect(actual).toEqual([new Uint8(0), new Uint8(1), new Uint8(0)]);
     });
 
     it('Works on field elements', async () => {
@@ -120,7 +120,7 @@ describe('Comparators', () => {
       ].forEach(i => i.execute(context));
 
       const actual = context.machineState.memory.getSlice(/*offset=*/ 10, /*size=*/ 4);
-      expect(actual).toEqual([new Field(0), new Field(1), new Field(0)]);
+      expect(actual).toEqual([new Uint8(0), new Uint8(1), new Uint8(0)]);
     });
 
     it('InTag is checked', async () => {
@@ -171,7 +171,7 @@ describe('Comparators', () => {
       ].forEach(i => i.execute(context));
 
       const actual = context.machineState.memory.getSlice(/*offset=*/ 10, /*size=*/ 4);
-      expect(actual).toEqual([new Uint32(1), new Uint32(1), new Uint32(0)]);
+      expect(actual).toEqual([new Uint8(1), new Uint8(1), new Uint8(0)]);
     });
 
     it('Works on field elements', async () => {
@@ -184,7 +184,7 @@ describe('Comparators', () => {
       ].forEach(i => i.execute(context));
 
       const actual = context.machineState.memory.getSlice(/*offset=*/ 10, /*size=*/ 4);
-      expect(actual).toEqual([new Field(1), new Field(1), new Field(0)]);
+      expect(actual).toEqual([new Uint8(1), new Uint8(1), new Uint8(0)]);
     });
 
     it('InTag is checked', async () => {

diff --git a/yarn-project/simulator/src/avm/opcodes/comparators.ts b/yarn-project/simulator/src/avm/opcodes/comparators.ts
@@ -1,5 +1,5 @@
 import type { AvmContext } from '../avm_context.js';
-import { TaggedMemory } from '../avm_memory_types.js';
+import { Uint8 } from '../avm_memory_types.js';
 import { Opcode } from '../serialization/instruction_serialization.js';
 import { ThreeOperandInstruction } from './instruction_impl.js';
 
@@ -17,7 +17,7 @@ export class Eq extends ThreeOperandInstruction {
     const a = context.machineState.memory.get(this.aOffset);
     const b = context.machineState.memory.get(this.bOffset);
 
-    const dest = TaggedMemory.buildFromTagOrDie(a.equals(b) ? 1n : 0n, this.inTag);
+    const dest = new Uint8(a.equals(b) ? 1 : 0);
     context.machineState.memory.set(this.dstOffset, dest);
 
     context.machineState.incrementPc();
@@ -38,7 +38,7 @@ export class Lt extends ThreeOperandInstruction {
     const a = context.machineState.memory.get(this.aOffset);
     const b = context.machineState.memory.get(this.bOffset);
 
-    const dest = TaggedMemory.buildFromTagOrDie(a.lt(b) ? 1n : 0n, this.inTag);
+    const dest = new Uint8(a.lt(b) ? 1 : 0);
     context.machineState.memory.set(this.dstOffset, dest);
 
     context.machineState.incrementPc();
@@ -59,7 +59,7 @@ export class Lte extends ThreeOperandInstruction {
     const a = context.machineState.memory.get(this.aOffset);
     const b = context.machineState.memory.get(this.bOffset);
 
-    const dest = TaggedMemory.buildFromTagOrDie(a.lt(b) || a.equals(b) ? 1n : 0n, this.inTag);
+    const dest = new Uint8(a.lt(b) || a.equals(b) ? 1 : 0);
     context.machineState.memory.set(this.dstOffset, dest);
 
     context.machineState.incrementPc();

diff --git a/yellow-paper/docs/public-vm/gen/_instruction-set.mdx b/yellow-paper/docs/public-vm/gen/_instruction-set.mdx
@@ -604,7 +604,7 @@ Equality check (a == b)
 	- **dstOffset**: memory offset specifying where to store operation's result
 - **Expression**: `M[dstOffset] = M[aOffset] == M[bOffset] ? 1 : 0`
 - **Tag checks**: `T[aOffset] == T[bOffset] == inTag`
-- **Tag updates**: `T[dstOffset] = inTag`
+- **Tag updates**: `T[dstOffset] = u8`
 - **Bit-size**: 128
 
 [![](./images/bit-formats/EQ.png)](./images/bit-formats/EQ.png)
@@ -625,7 +625,7 @@ Less-than check (a < b)
 	- **dstOffset**: memory offset specifying where to store operation's result
 - **Expression**: `M[dstOffset] = M[aOffset] < M[bOffset] ? 1 : 0`
 - **Tag checks**: `T[aOffset] == T[bOffset] == inTag`
-- **Tag updates**: `T[dstOffset] = inTag`
+- **Tag updates**: `T[dstOffset] = u8`
 - **Bit-size**: 128
 
 [![](./images/bit-formats/LT.png)](./images/bit-formats/LT.png)
@@ -646,7 +646,7 @@ Less-than-or-equals check (a <= b)
 	- **dstOffset**: memory offset specifying where to store operation's result
 - **Expression**: `M[dstOffset] = M[aOffset] <= M[bOffset] ? 1 : 0`
 - **Tag checks**: `T[aOffset] == T[bOffset] == inTag`
-- **Tag updates**: `T[dstOffset] = inTag`
+- **Tag updates**: `T[dstOffset] = u8`
 - **Bit-size**: 128
 
 [![](./images/bit-formats/LTE.png)](./images/bit-formats/LTE.png)

diff --git a/yellow-paper/src/preprocess/InstructionSet/InstructionSet.js b/yellow-paper/src/preprocess/InstructionSet/InstructionSet.js
@@ -140,7 +140,7 @@ const INSTRUCTION_SET_RAW = [
         "Summary": "Equality check (a == b)",
         "Details": "",
         "Tag checks": "`T[aOffset] == T[bOffset] == inTag`",
-        "Tag updates": "`T[dstOffset] = inTag`",
+        "Tag updates": "`T[dstOffset] = u8`",
     },
     {
         "id": "lt",
@@ -159,7 +159,7 @@ const INSTRUCTION_SET_RAW = [
         "Summary": "Less-than check (a < b)",
         "Details": "",
         "Tag checks": "`T[aOffset] == T[bOffset] == inTag`",
-        "Tag updates": "`T[dstOffset] = inTag`",
+        "Tag updates": "`T[dstOffset] = u8`",
     },
     {
         "id": "lte",
@@ -178,7 +178,7 @@ const INSTRUCTION_SET_RAW = [
         "Summary": "Less-than-or-equals check (a <= b)",
         "Details": "",
         "Tag checks": "`T[aOffset] == T[bOffset] == inTag`",
-        "Tag updates": "`T[dstOffset] = inTag`",
+        "Tag updates": "`T[dstOffset] = u8`",
     },
     {
         "id": "and",