diff --git a/compiler/forget/src/HIR/SSAify.ts b/compiler/forget/src/HIR/SSAify.ts
index ec2e3a6ede..984ec93d24 100644
--- a/compiler/forget/src/HIR/SSAify.ts
+++ b/compiler/forget/src/HIR/SSAify.ts
@@ -165,11 +165,11 @@ class SSABuilder {
 
 export default function buildSSA(func: HIRFunction, env: Environment) {
   const builder = new SSABuilder(env);
-  function visit(blockId: BlockId) {
-    const block = func.body.blocks.get(blockId)!;
-    if (builder.visitedBlocks.has(block)) {
-      return;
-    }
+  for (const [blockId, block] of func.body.blocks) {
+    invariant(
+      !builder.visitedBlocks.has(block),
+      `found a cycle! visiting bb${block.id} again`
+    );
     builder.visitedBlocks.add(block);
 
     builder.startBlock(block);
@@ -208,13 +208,7 @@ export default function buildSSA(func: HIRFunction, env: Environment) {
         builder.fixIncompletePhis(output);
       }
     }
-
-    for (const output of outputs) {
-      visit(output);
-    }
   }
-
-  visit(func.body.entry);
 }
 
 function rewriteUsesAndCollectOutputs(
@@ -245,7 +239,7 @@ function rewriteUsesAndCollectOutputs(
     case "switch": {
       const { cases } = terminal;
       terminal.test = builder.getPlace(terminal.test);
-      for (const case_ of [...cases].reverse()) {
+      for (const case_ of [...cases]) {
         if (case_.test) {
           case_.test = builder.getPlace(case_.test);
         }
diff --git a/compiler/forget/src/__tests__/fixtures/hir/ssa-complex-multiple-if.expect.md b/compiler/forget/src/__tests__/fixtures/hir/ssa-complex-multiple-if.expect.md
index f2645a899d..e2e54e6a7e 100644
--- a/compiler/forget/src/__tests__/fixtures/hir/ssa-complex-multiple-if.expect.md
+++ b/compiler/forget/src/__tests__/fixtures/hir/ssa-complex-multiple-if.expect.md
@@ -28,23 +28,23 @@ bb0:
   If (read $10) then:bb2 else:bb1
 bb2:
   predecessor blocks: bb0
-  Reassign mutate x$18 = 3
+  Reassign mutate x$11 = 3
   Goto bb1
 bb1:
   predecessor blocks: bb0 bb2
-  y$12: phi(bb0: y$8, bb2: y$8)
-  x$17: phi(bb0: x$7, bb2: x$18)
-  Const mutate $11 = 3
-  Const mutate $13 = Binary read y$12 === read $11
-  If (read $13) then:bb4 else:bb3
+  y$13: phi(bb0: y$8, bb2: y$8)
+  x$17: phi(bb0: x$7, bb2: x$11)
+  Const mutate $12 = 3
+  Const mutate $14 = Binary read y$13 === read $12
+  If (read $14) then:bb4 else:bb3
 bb4:
   predecessor blocks: bb1
-  Reassign mutate x$16 = 5
+  Reassign mutate x$15 = 5
   Goto bb3
 bb3:
   predecessor blocks: bb1 bb4
-  x$14: phi(bb1: x$17, bb4: x$16)
-  Reassign mutate y$15 = read x$14
+  x$16: phi(bb1: x$17, bb4: x$15)
+  Reassign mutate y$18 = read x$16
   Return
 ```
 
@@ -55,16 +55,16 @@ function foo$0() {
   let x$7 = 1;
   let y$8 = 2;
   if (y$8 === 2) {
-    x$18 = 3;
+    x$11 = 3;
     ("<<TODO: handle complex control flow in codegen>>");
   }
 
-  if (y$12 === 3) {
-    x$16 = 5;
+  if (y$13 === 3) {
+    x$15 = 5;
     ("<<TODO: handle complex control flow in codegen>>");
   }
 
-  y$15 = x$14;
+  y$18 = x$16;
   return;
 }
 
diff --git a/compiler/forget/src/__tests__/fixtures/hir/ssa-complex-single-if.expect.md b/compiler/forget/src/__tests__/fixtures/hir/ssa-complex-single-if.expect.md
index c0d9ee8994..4a62eaf600 100644
--- a/compiler/forget/src/__tests__/fixtures/hir/ssa-complex-single-if.expect.md
+++ b/compiler/forget/src/__tests__/fixtures/hir/ssa-complex-single-if.expect.md
@@ -25,12 +25,12 @@ bb0:
   If (read $8) then:bb2 else:bb1
 bb2:
   predecessor blocks: bb0
-  Reassign mutate x$11 = 3
+  Reassign mutate x$9 = 3
   Goto bb1
 bb1:
   predecessor blocks: bb0 bb2
-  x$9: phi(bb0: x$5, bb2: x$11)
-  Reassign mutate y$10 = read x$9
+  x$10: phi(bb0: x$5, bb2: x$9)
+  Reassign mutate y$11 = read x$10
   Return
 ```
 
@@ -41,11 +41,11 @@ function foo$0() {
   let x$5 = 1;
   let y$6 = 2;
   if (y$6 === 2) {
-    x$11 = 3;
+    x$9 = 3;
     ("<<TODO: handle complex control flow in codegen>>");
   }
 
-  y$10 = x$9;
+  y$11 = x$10;
   return;
 }
 
diff --git a/compiler/forget/src/__tests__/fixtures/hir/ssa-if-else.expect.md b/compiler/forget/src/__tests__/fixtures/hir/ssa-if-else.expect.md
index 093e804a89..13a758602d 100644
--- a/compiler/forget/src/__tests__/fixtures/hir/ssa-if-else.expect.md
+++ b/compiler/forget/src/__tests__/fixtures/hir/ssa-if-else.expect.md
@@ -24,11 +24,11 @@ bb0:
   If (read y$6) then:bb2 else:bb3
 bb2:
   predecessor blocks: bb0
-  Let mutate z$8 = Binary read x$5 + read y$6
+  Let mutate z$7 = Binary read x$5 + read y$6
   Goto bb1
 bb3:
   predecessor blocks: bb0
-  Let mutate z$7 = read x$5
+  Let mutate z$8 = read x$5
   Goto bb1
 bb1:
   predecessor blocks: bb3 bb2
@@ -42,10 +42,10 @@ function foo$0() {
   let x$5 = 1;
   let y$6 = 2;
   if (y$6) {
-    let z$8 = x$5 + y$6;
+    let z$7 = x$5 + y$6;
     ("<<TODO: handle complex control flow in codegen>>");
   } else {
-    let z$7 = x$5;
+    let z$8 = x$5;
     ("<<TODO: handle complex control flow in codegen>>");
   }
 
diff --git a/compiler/forget/src/__tests__/fixtures/hir/ssa-objectexpression-phi.expect.md b/compiler/forget/src/__tests__/fixtures/hir/ssa-objectexpression-phi.expect.md
index f07f39dbc7..de9c059128 100644
--- a/compiler/forget/src/__tests__/fixtures/hir/ssa-objectexpression-phi.expect.md
+++ b/compiler/forget/src/__tests__/fixtures/hir/ssa-objectexpression-phi.expect.md
@@ -29,18 +29,18 @@ bb0:
   If (read $9) then:bb2 else:bb3
 bb2:
   predecessor blocks: bb0
-  Reassign mutate x$14 = 2
+  Reassign mutate x$10 = 2
   Goto bb1
 bb3:
   predecessor blocks: bb0
-  Reassign mutate y$10 = 3
+  Reassign mutate y$11 = 3
   Goto bb1
 bb1:
   predecessor blocks: bb3 bb2
-  x$11: phi(bb3: x$6, bb2: x$14)
-  y$12: phi(bb3: y$10, bb2: y$7)
-  Let mutate t$13 = Object { x: read x$11, y: read y$12 }
-  Return freeze t$13
+  x$12: phi(bb3: x$6, bb2: x$10)
+  y$13: phi(bb3: y$11, bb2: y$7)
+  Let mutate t$14 = Object { x: read x$12, y: read y$13 }
+  Return freeze t$14
 ```
 
 ## Code
@@ -50,18 +50,18 @@ function foo$0() {
   let x$6 = 1;
   let y$7 = 2;
   if (x$6 > 1) {
-    x$14 = 2;
+    x$10 = 2;
     ("<<TODO: handle complex control flow in codegen>>");
   } else {
-    y$10 = 3;
+    y$11 = 3;
     ("<<TODO: handle complex control flow in codegen>>");
   }
 
-  let t$13 = {
-    x: x$11,
-    y: y$12,
+  let t$14 = {
+    x: x$12,
+    y: y$13,
   };
-  return t$13;
+  return t$14;
 }
 
 ```
diff --git a/compiler/forget/src/__tests__/fixtures/hir/ssa-return.expect.md b/compiler/forget/src/__tests__/fixtures/hir/ssa-return.expect.md
index 903e21e10d..4bf1b0294f 100644
--- a/compiler/forget/src/__tests__/fixtures/hir/ssa-return.expect.md
+++ b/compiler/forget/src/__tests__/fixtures/hir/ssa-return.expect.md
@@ -23,12 +23,12 @@ bb0:
   If (read $6) then:bb2 else:bb1
 bb2:
   predecessor blocks: bb0
-  Reassign mutate x$8 = 2
+  Reassign mutate x$7 = 2
   Goto bb1
 bb1:
   predecessor blocks: bb0 bb2
-  x$7: phi(bb0: x$4, bb2: x$8)
-  Return read x$7
+  x$8: phi(bb0: x$4, bb2: x$7)
+  Return read x$8
 ```
 
 ## Code
@@ -37,11 +37,11 @@ bb1:
 function foo$0() {
   let x$4 = 1;
   if (x$4 === 1) {
-    x$8 = 2;
+    x$7 = 2;
     ("<<TODO: handle complex control flow in codegen>>");
   }
 
-  return x$7;
+  return x$8;
 }
 
 ```
diff --git a/compiler/forget/src/__tests__/fixtures/hir/ssa-simple-phi.expect.md b/compiler/forget/src/__tests__/fixtures/hir/ssa-simple-phi.expect.md
index e45cdabb4f..11c54248d1 100644
--- a/compiler/forget/src/__tests__/fixtures/hir/ssa-simple-phi.expect.md
+++ b/compiler/forget/src/__tests__/fixtures/hir/ssa-simple-phi.expect.md
@@ -26,16 +26,16 @@ bb0:
   If (read $7) then:bb2 else:bb3
 bb2:
   predecessor blocks: bb0
-  Reassign mutate y$11 = 1
+  Reassign mutate y$8 = 1
   Goto bb1
 bb3:
   predecessor blocks: bb0
-  Reassign mutate y$8 = 2
+  Reassign mutate y$9 = 2
   Goto bb1
 bb1:
   predecessor blocks: bb3 bb2
-  y$9: phi(bb3: y$8, bb2: y$11)
-  Let mutate x$10 = read y$9
+  y$10: phi(bb3: y$9, bb2: y$8)
+  Let mutate x$11 = read y$10
   Return
 ```
 
@@ -45,14 +45,14 @@ bb1:
 function foo$0() {
   let y$5 = 2;
   if (y$5 > 1) {
-    y$11 = 1;
+    y$8 = 1;
     ("<<TODO: handle complex control flow in codegen>>");
   } else {
-    y$8 = 2;
+    y$9 = 2;
     ("<<TODO: handle complex control flow in codegen>>");
   }
 
-  let x$10 = y$9;
+  let x$11 = y$10;
   return;
 }
 
diff --git a/compiler/forget/src/__tests__/fixtures/hir/ssa-switch.expect.md b/compiler/forget/src/__tests__/fixtures/hir/ssa-switch.expect.md
index 9d54b2ee40..537adb4939 100644
--- a/compiler/forget/src/__tests__/fixtures/hir/ssa-switch.expect.md
+++ b/compiler/forget/src/__tests__/fixtures/hir/ssa-switch.expect.md
@@ -39,23 +39,23 @@ bb0:
     Default: bb2
 bb5:
   predecessor blocks: bb0
-  Const mutate $21 = 1
-  Reassign mutate x$22 = Binary read x$10 + read $21
+  Const mutate $15 = 1
+  Reassign mutate x$16 = Binary read x$10 + read $15
   Goto bb1
 bb3:
   predecessor blocks: bb0
-  Const mutate $19 = 2
-  Reassign mutate x$20 = Binary read x$10 + read $19
+  Const mutate $17 = 2
+  Reassign mutate x$18 = Binary read x$10 + read $17
   Goto bb1
 bb2:
   predecessor blocks: bb0
-  Const mutate $15 = 3
-  Reassign mutate x$16 = Binary read x$10 + read $15
+  Const mutate $19 = 3
+  Reassign mutate x$20 = Binary read x$10 + read $19
   Goto bb1
 bb1:
   predecessor blocks: bb5 bb3 bb2
-  x$17: phi(bb5: x$22, bb3: x$20, bb2: x$16)
-  Let mutate y$18 = read x$17
+  x$21: phi(bb5: x$16, bb3: x$18, bb2: x$20)
+  Let mutate y$22 = read x$21
   Return
 ```
 
@@ -66,22 +66,22 @@ function foo$0() {
   let x$10 = 1;
   switch (x$10) {
     case x$10 === 1: {
-      x$22 = x$10 + 1;
+      x$16 = x$10 + 1;
       ("<<TODO: handle complex control flow in codegen>>");
     }
 
     case x$10 === 2: {
-      x$20 = x$10 + 2;
+      x$18 = x$10 + 2;
       ("<<TODO: handle complex control flow in codegen>>");
     }
 
     default: {
-      x$16 = x$10 + 3;
+      x$20 = x$10 + 3;
       ("<<TODO: handle complex control flow in codegen>>");
     }
   }
 
-  let y$18 = x$17;
+  let y$22 = x$21;
   return;
 }
 
diff --git a/compiler/forget/src/__tests__/fixtures/hir/ssa-throw.expect.md b/compiler/forget/src/__tests__/fixtures/hir/ssa-throw.expect.md
index e2d0a00e33..5b5dfc127a 100644
--- a/compiler/forget/src/__tests__/fixtures/hir/ssa-throw.expect.md
+++ b/compiler/forget/src/__tests__/fixtures/hir/ssa-throw.expect.md
@@ -22,12 +22,12 @@ bb0:
   If (read $6) then:bb2 else:bb1
 bb2:
   predecessor blocks: bb0
-  Reassign mutate x$8 = 2
+  Reassign mutate x$7 = 2
   Goto bb1
 bb1:
   predecessor blocks: bb0 bb2
-  x$7: phi(bb0: x$4, bb2: x$8)
-  Throw read x$7
+  x$8: phi(bb0: x$4, bb2: x$7)
+  Throw read x$8
 ```
 
 ## Code
@@ -36,11 +36,11 @@ bb1:
 function foo$0() {
   let x$4 = 1;
   if (x$4 === 1) {
-    x$8 = 2;
+    x$7 = 2;
     ("<<TODO: handle complex control flow in codegen>>");
   }
 
-  throw x$7;
+  throw x$8;
 }
 
 ```