compiler: unroll small array hash/equal instead of looping

Author: jakebailey

compiler/map.go

@@ -10,6 +10,8 @@ import (
 	"tinygo.org/x/go-llvm"
 )
 
+const hashArrayUnrollLimit = 4
+
 // createMakeMap creates a new map object (runtime.hashmap) by allocating and
 // initializing an appropriately sized object.
 func (b *builder) createMakeMap(expr *ssa.MakeMap) (llvm.Value, error) {
@@ -559,8 +561,17 @@ func (b *builder) generateKeyHash(keyType types.Type, llvmKeyType llvm.Type, key
 		if arrayLen == 0 {
 			return llvm.ConstInt(b.ctx.Int32Type(), 0, false)
 		}
-		// Non-binary elements: generate a loop to avoid code explosion
-		// for large arrays.
+		if arrayLen <= hashArrayUnrollLimit {
+			hash := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
+			zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
+			for i := 0; i < int(arrayLen); i++ {
+				idx := llvm.ConstInt(b.uintptrType, uint64(i), false)
+				elemPtr := b.CreateInBoundsGEP(llvmKeyType, keyPtr, []llvm.Value{zero, idx}, "")
+				elemHash := b.generateKeyHash(elemType, llvmElemType, elemPtr, seed)
+				hash = b.CreateXor(hash, elemHash, "")
+			}
+			return hash
+		}
 		initHash := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
 		zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
 
@@ -672,7 +683,18 @@ func (b *builder) generateKeyEqual(keyType types.Type, llvmKeyType llvm.Type, xP
 		if arrayLen == 0 {
 			return llvm.ConstInt(b.ctx.Int1Type(), 1, false)
 		}
-		// Non-binary elements: generate a loop with short-circuit exit.
+		if arrayLen <= hashArrayUnrollLimit {
+			result := llvm.ConstInt(b.ctx.Int1Type(), 1, false)
+			zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
+			for i := 0; i < int(arrayLen); i++ {
+				idx := llvm.ConstInt(b.uintptrType, uint64(i), false)
+				xElemPtr := b.CreateInBoundsGEP(llvmKeyType, xPtr, []llvm.Value{zero, idx}, "")
+				yElemPtr := b.CreateInBoundsGEP(llvmKeyType, yPtr, []llvm.Value{zero, idx}, "")
+				elemEq := b.generateKeyEqual(elemType, llvmElemType, xElemPtr, yElemPtr, fn)
+				result = b.CreateAnd(result, elemEq, "")
+			}
+			return result
+		}
 		zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
 
 		loopEntry := b.GetInsertBlock()