boot2

commit 5344093cdf6b73c444dbd42242b03dea455076ea
parent a3869ad6ec05587cfa7835042f2f8ab305be2f06
Author: Ryan Sepassi <rsepassi@gmail.com>
Date:   Mon, 27 Apr 2026 04:01:53 -0700

scheme1: add (heap-usage) primitive returning bytes consumed

Returns (heap_next - heap_buf_ptr) as a tagged fixnum. Used by cc to
instrument per-phase compile-time allocation cost.

Implementation note: M0 appends a NUL byte to every \"...\" string
literal, so adding a 10-byte name like "heap-usage" emits 11 bytes
and breaks 8-alignment of subsequent data slots (the prim_table $()
size fields, the bss pointer slots like :heap_buf_ptr) -- causing
bus errors at startup. Pad with 5 explicit '00' bytes so the total
addition is 16 bytes (multiple of 8). Verified with a small (cons
1 (cons 2 (cons 3 '()))) test: usage rose from 2488 to 3224 bytes.

Diffstat:
M
scheme1/scheme1.P1pp
 | 
15
+++++++++++++++

1 file changed, 15 insertions(+), 0 deletions(-)
diff --git a/scheme1/scheme1.P1pp b/scheme1/scheme1.P1pp
@@ -4801,6 +4801,16 @@
     %ret
 %endscope
 
+# (heap-usage) -> tagged fixnum: bytes consumed since heap_init
+# (heap_next - heap_buf_ptr). Used by cc to instrument per-phase
+# allocation cost. Args list ignored.
+:prim_heap_usage_entry
+    %ld_global(t0, &heap_next)
+    %ld_global(t1, &heap_buf_ptr)
+    %sub(a0, t0, t1)
+    %mkfix(a0, a0)
+    %ret
+
 # Surface names. Length is hard-coded at the call site; no NUL needed
 # because intern takes (ptr, len). Aligned padding via "\0" bytes is
 # fine -- M0 emits ASCII verbatim.
@@ -4886,6 +4896,10 @@
 :name_write       "write"
 :name_error       "error"
 :name_format      "format"
+;; "heap-usage" + auto-NUL = 11 bytes; pad to 16 (multiple of 8) so
+;; subsequent 8-aligned data slots (prim_table $() rows, the bss
+;; pointer slots) stay aligned. M0 appends a NUL to every "..." string.
+:name_heap_usage  "heap-usage" '00' '00' '00' '00' '00'
 
 # Writer string constants. Lengths are hard-coded at the bv_putn call
 # sites (write_to_bv branches). No NUL needed -- bv_putn takes (ptr, n).
@@ -4964,6 +4978,7 @@
 &name_write       %(0)  $(5)   &prim_write_entry        %(0)
 &name_error       %(0)  $(5)   &prim_error_entry        %(0)
 &name_format      %(0)  $(6)   &prim_format_entry       %(0)
+&name_heap_usage  %(0)  $(10)  &prim_heap_usage_entry   %(0)
 :prim_table_end
 
 :msg_usage          "scheme1: usage: scheme1 SOURCE.scm" '0a' '00'