From e58a77d528cfe10dd4fc0aeb4abb2180e14659e0 Mon Sep 17 00:00:00 2001
From: Kartik Agaram <vc@akkartik.com>
Date: Tue, 10 Mar 2020 16:34:42 -0700
Subject: 6117 - fix offset computation

It makes no sense to know where the next variable will start before I've
seen it or how much space it needs. Things have only been working so far
because all variables take 4 bytes.
---
 apps/mu.subx | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/apps/mu.subx b/apps/mu.subx
index 4a4bde35..2a3d331d 100644
--- a/apps/mu.subx
+++ b/apps/mu.subx
@@ -6090,8 +6090,8 @@ $type-equal?:end:
 
 Curr-block-depth:  # (addr int)
     0/imm32
-Next-local-stack-offset:  # (addr int)
-    -4/imm32
+Curr-local-stack-offset:  # (addr int)
+    0/imm32
 
 == code
 
@@ -6151,12 +6151,12 @@ emit-subx-function:  # out: (addr buffered-file), f: (handle function)
     (write-buffered %edi ":\n")
     # initialize some global state
     c7 0/subop/copy *Curr-block-depth 1/imm32
-    c7 0/subop/copy *Next-local-stack-offset -4/imm32
+    c7 0/subop/copy *Curr-local-stack-offset 0/imm32
     #
     (emit-subx-prologue %edi)
     (emit-subx-block %edi *(ecx+0x10) %edx)  # Function-body
     (emit-subx-epilogue %edi)
-    # TODO: validate that *Curr-block-depth and *Next-local-stack-offset have
+    # TODO: validate that *Curr-block-depth and *Curr-local-stack-offset have
     # been cleaned up
 $emit-subx-function:end:
     # . reclaim locals
@@ -6425,8 +6425,8 @@ compute-reg-and-maybe-emit-spill:  # out: (addr buffered-file), stmt: (handle re
     3d/compare-eax-and 0/imm32/false
     75/jump-if-!= $compute-reg-and-maybe-emit-spill:end/disp8
     # TODO: assert(sizeof(output) == 4)
-    # *Next-local-stack-offset -= 4
-    81 5/subop/subtract *Next-local-stack-offset 4/imm32
+    # *Curr-local-stack-offset -= 4
+    81 5/subop/subtract *Curr-local-stack-offset 4/imm32
     # emit spill
     (emit-indent *(ebp+8) *Curr-block-depth)
     (write-buffered *(ebp+8) "ff 6/subop/push %")
@@ -6961,13 +6961,13 @@ $clean-up-blocks:reclaim-loop:
       # if (v->block-depth < until-block-depth) break
       39/compare *(eax+8) 1/r32/ecx  # Var-block-depth
       7c/jump-if-< break/disp8
-      # if v is on the stack, update Next-local-stack-offset
+      # if v is on the stack, update Curr-local-stack-offset
       81 7/subop/compare *(eax+0x10) 0/imm32  # Var-register
       {
         75/jump-if-!= break/disp8
 $clean-up-blocks:reclaim-var-on-stack:
         (size-of %eax)  # => eax
-        01/add *Next-local-stack-offset 0/r32/eax
+        01/add *Curr-local-stack-offset 0/r32/eax
       }
       (pop %esi)
       e9/jump loop/disp32
@@ -6989,20 +6989,21 @@ emit-subx-var-def:  # out: (addr buffered-file), stmt: (handle stmt)
     # . save registers
     50/push-eax
     51/push-ecx
+    52/push-edx
     # eax = stmt
     8b/-> *(ebp+0xc) 0/r32/eax
     # var v/ecx: (handle var)
     8b/-> *(eax+4) 1/r32/ecx
-    # v->offset = *Next-local-stack-offset
-    8b/-> *Next-local-stack-offset 0/r32/eax
-    89/<- *(ecx+0xc) 0/r32/eax  # Var-offset
     # v->block-depth = *Curr-block-depth
     8b/-> *Curr-block-depth 0/r32/eax
     89/<- *(ecx+8) 0/r32/eax  # Var-block-depth
     # var n/eax: int = size-of(stmt->var)
     (size-of %ecx)  # Vardef-var => eax
-    # *Next-local-stack-offset -= n
-    29/subtract-from *Next-local-stack-offset 0/r32/eax
+    # *Curr-local-stack-offset -= n
+    29/subtract-from *Curr-local-stack-offset 0/r32/eax
+    # v->offset = *Curr-local-stack-offset
+    8b/-> *Curr-local-stack-offset 2/r32/edx
+    89/<- *(ecx+0xc) 2/r32/edx  # Var-offset
     # while n > 0
     {
       3d/compare-eax-with 0/imm32
@@ -7016,6 +7017,7 @@ emit-subx-var-def:  # out: (addr buffered-file), stmt: (handle stmt)
     }
 $emit-subx-var-def:end:
     # . restore registers
+    5a/pop-to-edx
     59/pop-to-ecx
     58/pop-to-eax
     # . epilogue
-- 
cgit 1.4.1-2-gfad0