5982 - start putting block labels on the var stack

Before:
  we detected labels using a '$' at the start of an arg, and turned them
  into literals.

After:
  we put labels on the var stack and let the regular lookup of the var
  stack handle labels.

This adds complexity in one place and removes it from another. The crucial
benefit is that it allows us to store a block depth for each label. That
will come in handy later.

All this works only because of a salubrious coincidence: Mu labels are
always at the start of a block, and jumps always refer to the name at the
start of a block, even when the jump is in the forwards direction. So we
never see label uses before definitions.

Note on CI: this currently only works natively, not emulated.

2 files changed, 41 insertions, 26 deletions

diff --git a/apps/mu b/apps/mu
index b254e2e4..68716f88 100755
--- a/apps/mu
+++ b/apps/mu
Binary files differdiff --git a/apps/mu.subx b/apps/mu.subx
index f2326284..367fa3d9 100644
--- a/apps/mu.subx
+++ b/apps/mu.subx
@@ -3053,7 +3053,11 @@ $check-no-tokens-left:end:
 
 parse-mu-named-block:  # name: (addr slice), in: (addr buffered-file), vars: (addr stack (handle var)), fn: (handle function) -> result/eax: (handle stmt)
     # pseudocode:
+    #   var v: (handle var) = new-var(name except trailing ':', 0)
+    #   v->block-depth = *Curr-block-depth  # containing block depth
+    #   push(vars, v)
     #   result = parse-mu-block(in, vars, fn)
+    #   pop(vars)
     #   result->tag = named-block
     #   result->name = slice-to-string(name)
     #   return result
@@ -3063,17 +3067,43 @@ parse-mu-named-block:  # name: (addr slice), in: (addr buffered-file), vars: (ad
     89/<- %ebp 4/r32/esp
     # . save registers
     51/push-ecx
-    # var s/ecx: (addr array byte) = slice-to-string(name)
-    (slice-to-string Heap *(ebp+8))  # => eax
-    89/<- %ecx 0/r32/eax
-    #
+    57/push-edi
+    # push a var for the label on to 'vars'
+    {
+      # ecx = name
+      8b/-> *(ebp+8) 1/r32/ecx
+      # var s/ecx: slice = {name->start, name->end}
+      ff 6/subop/push *(ecx+4)  # Slice-end
+      ff 6/subop/push *ecx  # Slice-start
+      89/<- %ecx 4/r32/esp
+      # strip the trailing ':' from s
+      ff 1/subop/decrement *(ecx+4)
+      # var s/ecx: (address array byte)
+      (slice-to-string Heap %ecx)  # => eax
+      89/<- %ecx 0/r32/eax
+      # var type/eax: (handle tree type-id) = literal
+      (allocate Heap *Tree-size)  # => eax
+      (zero-out %eax *Tree-size)  # default type is 'literal'
+      # var v: (handle var) = new-var(s)
+      (new-var Heap %ecx %eax *Curr-block-depth 0 0)  # => eax
+      # push(vars, v)
+      (push *(ebp+0x10) %eax)
+      # reclaim s
+      81 0/subop/add %esp 8/imm32
+    }
+    # edi = result
     (parse-mu-block *(ebp+0xc) *(ebp+0x10) *(ebp+0x14))  # => eax
+    89/<- %edi 0/r32/eax
+    (pop *(ebp+0x10))  # => eax
     # result->tag = named-block
-    c7 0/subop/copy *eax 4/imm32/named-block  # Stmt-tag
+    c7 0/subop/copy *edi 4/imm32/named-block  # Stmt-tag
     # result->name = slice-to-string(name)
-    89/<- *(eax+8) 1/r32/ecx  # Named-block-name
+    (slice-to-string Heap *(ebp+8))  # => eax
+    89/<- *(edi+8) 0/r32/eax  # Named-block-name
 $parse-mu-named-block:end:
+    89/<- %eax 7/r32/edi
     # . restore registers
+    5f/pop-to-edi
     59/pop-to-ecx
     # . epilogue
     89/<- %esp 5/r32/ebp
@@ -3337,26 +3367,7 @@ $add-operation-and-inputs-to-stmt:read-inouts:
       (slice-equal? %ecx "<-")
       3d/compare-eax-and 0/imm32
       0f 85/jump-if-!= $add-operation-and-inputs-to-stmt:abort/disp32
-      # if (name starts with "$") it's a label
-      {
-        # var eax: byte = name[0]
-        8b/-> *ecx 0/r32/eax
-        8a/copy-byte *eax 0/r32/AL
-        81 4/subop/and %eax 0xff/imm32
-        # if (eax != '$') goto next condition
-        3d/compare-eax-and 0x24/imm32/dollar
-        75/jump-if-!= break/disp8
-        # var eax: (handle var)
-        # labels aren't in vars; just create a new record on each use
-        (new-label Heap %ecx)  # => eax
-        # stmt->inouts = append(eax, stmt->inouts)
-        (append-list Heap %eax *(edi+8))  # Stmt1-inouts => eax
-        89/<- *(edi+8) 0/r32/eax  # Stmt1-inouts
-        # continue
-        e9/jump $add-operation-and-inputs-to-stmt:read-inouts/disp32
-      }
-$add-operation-and-inputs-to-stmt:regular-inout:
-      # otherwise
+      #
       (lookup-var-or-literal %ecx *(ebp+0x10))  # => eax
       (append-list Heap %eax *(edi+8))  # Stmt1-inouts or Regvardef-inouts => eax
       89/<- *(edi+8) 0/r32/eax  # Stmt1-inouts or Regvardef-inouts
@@ -4378,6 +4389,10 @@ $emit-cleanup-code:reclaim-var-in-register:
 $emit-cleanup-code:reclaim-var-on-stack:
         50/push-eax
         (size-of %ebx)  # => eax
+        # don't emit code for labels
+        3d/compare-eax-and 0/imm32
+        74/jump-if-= break/disp8
+        #
         (emit-indent *(ebp+8) *Curr-block-depth)
         (write-buffered *(ebp+8) "81 0/subop/add %esp ")
         (print-int32-buffered *(ebp+8) %eax)