From a4e5812454e3453e51998ab8928e7319b87b1249 Mon Sep 17 00:00:00 2001
From: SensanaMMZ <305674455+SensanaMMZ@users.noreply.github.com>
Date: Mon, 20 Jul 2026 11:21:01 -0400
Subject: [PATCH] Add opt-in register-allocation tracing (AGBCC_TRACE_ALLOC)

Emits one line per hard-register assignment in local and global allocation,
with the priority inputs (size, calls_crossed, live_length, n_refs). Gated on
the AGBCC_TRACE_ALLOC environment variable, so it is inert and does not affect
codegen unless explicitly enabled -- useful for understanding why the allocator
placed a value in a particular register when matching decompilations.
---
 gcc/global.c      | 12 ++++++++++++
 gcc/local-alloc.c | 10 +++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/gcc/global.c b/gcc/global.c
index d6a05263..46608b9b 100755
--- a/gcc/global.c
+++ b/gcc/global.c
@@ -1187,12 +1187,24 @@ find_reg (allocno, losers, alt_regs_p, accept_call_clobbered, retrying)
 
   /* Did we find a register?  */
 
+  if (best_reg < 0 && getenv ("AGBCC_TRACE_ALLOC"))
+    fprintf (stderr, "[galloc] pseudo %d -> SPILL (allocno %d, calls_crossed %d)\n",
+	     allocno_reg[allocno], allocno, (int) allocno_calls_crossed[allocno]);
+
   if (best_reg >= 0)
     {
       register int lim, j;
       HARD_REG_SET this_reg;
 
       /* Yes.  Record it as the hard register of this pseudo-reg.  */
+      if (getenv ("AGBCC_TRACE_ALLOC"))
+	fprintf (stderr,
+		 "[galloc] pseudo %d -> r%d  (allocno %d, size %d, calls_crossed %d, live_length %d, n_refs %d)\n",
+		 allocno_reg[allocno], best_reg, allocno,
+		 (int) allocno_size[allocno],
+		 (int) allocno_calls_crossed[allocno],
+		 (int) allocno_live_length[allocno],
+		 (int) allocno_n_refs[allocno]);
       reg_renumber[allocno_reg[allocno]] = best_reg;
       /* Also of any pseudo-regs that share with it.  */
       if (reg_may_share[allocno_reg[allocno]])
diff --git a/gcc/local-alloc.c b/gcc/local-alloc.c
index d4b45f01..6bfe23b7 100755
--- a/gcc/local-alloc.c
+++ b/gcc/local-alloc.c
@@ -1412,7 +1412,15 @@ block_alloc (b)
     if (qty_phys_reg[q] >= 0)
       {
 	for (i = qty_first_reg[q]; i >= 0; i = reg_next_in_qty[i])
-	  reg_renumber[i] = qty_phys_reg[q] + reg_offset[i];
+	  {
+	    if (getenv ("AGBCC_TRACE_ALLOC"))
+	      fprintf (stderr,
+		       "[lalloc] pseudo %d -> r%d  (qty %d, births %d, deaths %d, n_calls_crossed %d)\n",
+		       i, qty_phys_reg[q] + reg_offset[i], q,
+		       (int) qty_birth[q], (int) qty_death[q],
+		       (int) qty_n_calls_crossed[q]);
+	    reg_renumber[i] = qty_phys_reg[q] + reg_offset[i];
+	  }
       }
 }