From b01c25b76280a1739073616b4ad541a0f094528d Mon Sep 17 00:00:00 2001
From: Forest Belton <forest@homolo.gy>
Date: Wed, 22 Sep 2021 13:43:01 -0400
Subject: [PATCH] Precompute label indices

---
 lib/ir/block.ts | 12 ++++++++++++
 lib/regalloc.ts | 15 +--------------
 2 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/lib/ir/block.ts b/lib/ir/block.ts
index 789773e..08e89a5 100644
--- a/lib/ir/block.ts
+++ b/lib/ir/block.ts
@@ -3,9 +3,21 @@ import type { Loc } from "./loc"
 
 export class BasicBlock {
     insns: Array<AbsInsn2>
+    labels: { [label: string]: number }
 
     constructor(insns: Array<AbsInsn2>) {
         this.insns = insns
+        this.labels = this.insns
+            .reduce((labels, insn, i) => {
+                if (insn.type !== "label") {
+                    return labels
+                }
+
+                return {
+                    ...labels,
+                    [insn.dest]: i,
+                }
+            }, {})
     }
 
     locs(): Set<Loc> {
diff --git a/lib/regalloc.ts b/lib/regalloc.ts
index bd20d96..43aa7c6 100644
--- a/lib/regalloc.ts
+++ b/lib/regalloc.ts
@@ -41,7 +41,7 @@ export const liveness = (block: BasicBlock): LivenessInfo => {
                 continue
             }
 
-            const labelSet = info[getLabelIndex(block, block.insns[i].dest as string)]
+            const labelSet = info[block.labels[block.insns[i].dest as string]]
             if (setEquals(info[i], labelSet)) {
                 continue
             }
@@ -54,19 +54,6 @@ export const liveness = (block: BasicBlock): LivenessInfo => {
     return info
 }
 
-export const getLabelIndex = (block: BasicBlock, label: string): number => {
-    let idx = -1
-
-    for (let i = 0; i < block.insns.length; ++i) {
-        if (block.insns[i].type === "label" && block.insns[i].dest === label) {
-            idx = i
-            break
-        }
-    }
-
-    return idx
-}
-
 export const interference = (block: BasicBlock, live: LivenessInfo): Graph<Loc> =>
     createGraph((v, e) => {
         block.locs().forEach(loc => {