"ValueBlock" for while test node

The instructions of a while test node cannot just be pushed to the previous 
block. This creates a new block for the test node and then during code gen 
converts the statements pushed to the "value block" into expressions.

compiler/forget/src/HIR/Codegen.ts

@@ -100,6 +100,10 @@ class CodegenVisitor
     this.depth++;
     return [];
   }
+  enterValueBlock(): t.Statement[] {
+    this.depth++;
+    return [];
+  }
   visitValue(value: InstructionValue): t.Expression {
     return codegenInstructionValue(this.temp, value);
   }
@@ -237,6 +241,25 @@ class CodegenVisitor
     this.depth--;
     return t.blockStatement(block);
   }
+  leaveValueBlock(block: t.Statement[], place: t.Expression): t.Expression {
+    this.depth--;
+    if (block.length === 0) {
+      return place;
+    }
+    const expressions = block.map((stmt) => {
+      switch (stmt.type) {
+        case "ExpressionStatement":
+          return stmt.expression;
+        default:
+          todoInvariant(
+            false,
+            `Handle conversion of ${stmt.type} to expression`
+          );
+      }
+    });
+    expressions.push(place);
+    return t.sequenceExpression(expressions);
+  }
 }
 
 function codegenLabel(id: BlockId): string {

compiler/forget/src/HIR/HIRTreeVisitor.ts

@@ -239,15 +239,20 @@ class Driver<TBlock, TValue, TItem, TCase> {
           testTerminal.kind === "if",
           "Expected while loop test block to end in an if"
         );
-        // const bodyLength = blockValue.length;
+        const testValueBlock = this.visitor.enterValueBlock();
         for (const instr of testBlock.instructions) {
-          this.visitInstr(instr, blockValue);
+          const value = this.visitor.visitValue(instr.value, instr.id);
+          const item = this.visitor.visitInstruction(instr, value);
+          this.visitor.appendBlock(testValueBlock, item);
         }
-        // invariant(
-        //   body.length === bodyLength,
-        //   "Expected test to produce only temporaries"
-        // );
-        const testValue = this.visitPlace(testTerminal.test, terminal.id);
+        const testValueLast = this.visitor.visitValue(
+          testTerminal.test,
+          testTerminal.id
+        );
+        const testValue = this.visitor.leaveValueBlock(
+          testValueBlock,
+          testValueLast
+        );
         const fallthroughId =
           terminal.fallthrough !== null &&
           !this.cx.isScheduled(terminal.fallthrough)
@@ -644,6 +649,10 @@ export interface Visitor<TBlock, TValue, TItem, TCase> {
    */
   enterBlock(): TBlock;
 
+  enterValueBlock(): TBlock;
+
+  leaveValueBlock(block: TBlock, value: TValue): TValue;
+
   /**
    * Convert an InstructionValue into the visitor's own representation
    * of a value.

compiler/forget/src/HIR/InferReactiveScopeDependencies.ts

@@ -189,8 +189,12 @@ class ScopeDependenciesVisitor
   }
 
   enterBlock(): void {}
+  enterValueBlock(): void {}
   visitImplicitTerminal(): void | null {}
   visitCase(test: InstructionValue, block: void): void {}
   appendBlock(block: void, item: void, label?: BlockId | undefined): void {}
   leaveBlock(block: void): void {}
+  leaveValueBlock(block: void, value: InstructionValue): InstructionValue {
+    return value;
+  }
 }

compiler/forget/src/HIR/InferReactiveScopes.ts

@@ -254,6 +254,12 @@ class MergeOverlappingReactiveScopesVisitor
   enterBlock(): void {
     this.scopes.push(new BlockScope());
   }
+  enterValueBlock(): void {
+    this.enterBlock();
+  }
+  leaveValueBlock(block: void, value: void): void {
+    this.leaveBlock();
+  }
   visitValue(value: InstructionValue, id: InstructionId): void {
     this.visitId(id);
     for (const operand of eachInstructionValueOperand(value)) {
@@ -355,6 +361,14 @@ class AlignReactiveScopesToBlockScopeRangeVisitor
     }
   }
 
+  enterValueBlock(): void {
+    this.enterBlock();
+  }
+
+  leaveValueBlock(block: void, value: void): void {
+    this.leaveBlock();
+  }
+
   visitInstruction(instruction: Instruction, value: void): void {
     const scope = getInstructionScope(instruction);
     if (scope !== null) {

compiler/forget/src/HIR/PrintHIRTree.ts

@@ -32,6 +32,12 @@ class PrintVisitor implements Visitor<Array<string>, string, string, string> {
     this.depth++;
     return [];
   }
+  enterValueBlock(): string[] {
+    return this.enterBlock();
+  }
+  leaveValueBlock(block: string[], value: string): string {
+    return this.leaveBlock(block);
+  }
   visitValue(value: InstructionValue): string {
     return printMixedHIR(value);
   }

compiler/forget/src/__tests__/fixtures/hir/_bug_while-with-assignment.expect.md

@@ -31,7 +31,7 @@ bb1:
   sum$21_@3[0:14]: phi(bb0: sum$16_@3, bb3: sum$22_@3)
   [8] Reassign mutate value$18_@3[0:14] = Call mutate queue$14_@3.pop()
   [9] Const mutate $19_@6 = null
-  [10] Const mutate $20_@7[10:14] = Binary read value$18_@3 != read $19_@6
+  [10] Const mutate $20_@7[10:12] = Binary read value$18_@3 != read $19_@6
   [11] If (read $20_@7) then:bb3 else:bb2
 bb3:
   predecessor blocks: bb1
@@ -40,7 +40,7 @@ bb3:
 bb2:
   predecessor blocks: bb1
   [14] Return read sum$21_@3
-scope7 [10:14]:
+scope7 [10:12]:
  - read $19_@6
 ```
 
@@ -64,7 +64,7 @@ flowchart TB
     bb1_instrs["
       [8] Reassign mutate value$18_@3[0:14] = Call mutate queue$14_@3.pop()
       [9] Const mutate $19_@6 = null
-      [10] Const mutate $20_@7[10:14] = Binary read value$18_@3 != read $19_@6
+      [10] Const mutate $20_@7[10:12] = Binary read value$18_@3 != read $19_@6
     "]
     bb1_instrs --> bb1_terminal(["If (read $20_@7)"])
   end
@@ -95,8 +95,7 @@ function f$0(reader$1) {
   const queue$2 = [1, 2, 3];
   let value$6 = 0;
   let sum$7 = 0;
-  value$6 = queue$2.pop();
-  bb2: while (value$6 != null) {
+  bb2: while (((value$6 = queue$2.pop()), value$6 != null)) {
     sum$7 = sum$7 + value$6;
   }
 

compiler/forget/src/__tests__/fixtures/hir/mutable-lifetime-loops.expect.md

@@ -108,7 +108,7 @@ bb1:
   b$20_@0[0:23]: phi(bb0: b$14_@0, bb4: b$23_@0)
   c$22_@0[0:23]: phi(bb0: c$15_@0, bb4: c$25_@0)
   d$24_@0[0:23]: phi(bb0: d$16_@0, bb4: d$26_@0)
-  [6] Const mutate $17_@1[6:17] = true
+  [6] Const mutate $17_@1[6:8] = true
   [7] If (read $17_@1) then:bb3 else:bb2
 bb3:
   predecessor blocks: bb1
@@ -163,7 +163,7 @@ flowchart TB
   end
   subgraph bb1
     bb1_instrs["
-      [6] Const mutate $17_@1[6:17] = true
+      [6] Const mutate $17_@1[6:8] = true
     "]
     bb1_instrs --> bb1_terminal(["If (read $17_@1)"])
   end

compiler/forget/src/__tests__/fixtures/hir/mutable-liverange-loop.expect.md

@@ -99,7 +99,7 @@ bb0:
   [5] While test=bb1 loop=bb3 fallthrough=bb2
 bb1:
   predecessor blocks: bb0 bb4
-  [6] Const mutate $16_@2[6:12] = true
+  [6] Const mutate $16_@2[6:8] = true
   [7] If (read $16_@2) then:bb3 else:bb2
 bb3:
   predecessor blocks: bb1
@@ -145,7 +145,7 @@ flowchart TB
   end
   subgraph bb1
     bb1_instrs["
-      [6] Const mutate $16_@2[6:12] = true
+      [6] Const mutate $16_@2[6:8] = true
     "]
     bb1_instrs --> bb1_terminal(["If (read $16_@2)"])
   end

compiler/forget/src/__tests__/fixtures/hir/ssa-while-no-reassign.expect.md

@@ -17,12 +17,12 @@ function foo() {
 
 ```
 bb0:
-  [1] Let mutate x$5_@0[1:3] = 1
+  [1] Let mutate x$5_@0 = 1
   [2] While test=bb1 loop=bb3 fallthrough=bb2
 bb1:
   predecessor blocks: bb0 bb3
   [3] Const mutate $6_@1 = 10
-  [4] Const mutate $8_@2[4:9] = Binary read x$5_@0 < read $6_@1
+  [4] Const mutate $8_@2[4:6] = Binary read x$5_@0 < read $6_@1
   [5] If (read $8_@2) then:bb3 else:bb2
 bb3:
   predecessor blocks: bb1
@@ -32,7 +32,7 @@ bb3:
 bb2:
   predecessor blocks: bb1
   [9] Return read x$5_@0
-scope2 [4:9]:
+scope2 [4:6]:
  - read x$5_@0
  - read $6_@1
 scope3 [6:7]:
@@ -46,14 +46,14 @@ flowchart TB
   %% Basic Blocks
   subgraph bb0
     bb0_instrs["
-      [1] Let mutate x$5_@0[1:3] = 1
+      [1] Let mutate x$5_@0 = 1
     "]
     bb0_instrs --> bb0_terminal(["While"])
   end
   subgraph bb1
     bb1_instrs["
       [3] Const mutate $6_@1 = 10
-      [4] Const mutate $8_@2[4:9] = Binary read x$5_@0 < read $6_@1
+      [4] Const mutate $8_@2[4:6] = Binary read x$5_@0 < read $6_@1
     "]
     bb1_instrs --> bb1_terminal(["If (read $8_@2)"])
   end

compiler/forget/src/__tests__/fixtures/hir/ssa-while.expect.md

@@ -23,7 +23,7 @@ bb1:
   predecessor blocks: bb0 bb3
   x$7_@0[0:9]: phi(bb0: x$5_@0, bb3: x$10_@0)
   [3] Const mutate $6_@1 = 10
-  [4] Const mutate $8_@2[4:9] = Binary read x$7_@0 < read $6_@1
+  [4] Const mutate $8_@2[4:6] = Binary read x$7_@0 < read $6_@1
   [5] If (read $8_@2) then:bb3 else:bb2
 bb3:
   predecessor blocks: bb1
@@ -33,7 +33,7 @@ bb3:
 bb2:
   predecessor blocks: bb1
   [9] Return read x$7_@0
-scope2 [4:9]:
+scope2 [4:6]:
  - read $6_@1
 ```
 
@@ -51,7 +51,7 @@ flowchart TB
   subgraph bb1
     bb1_instrs["
       [3] Const mutate $6_@1 = 10
-      [4] Const mutate $8_@2[4:9] = Binary read x$7_@0 < read $6_@1
+      [4] Const mutate $8_@2[4:6] = Binary read x$7_@0 < read $6_@1
     "]
     bb1_instrs --> bb1_terminal(["If (read $8_@2)"])
   end