From 87c1d42cb389b91e2f41f1b5e0a11c859876101d Mon Sep 17 00:00:00 2001
From: Michael Pavone <pavone@retrodev.com>
Date: Sun, 7 Mar 2021 22:43:51 -0800
Subject: Fix bug in handling of MMAP_CODE regions smaller than 16KB

---
 backend.c     | 20 ++++++++++++++++----
 backend_x86.c | 10 ++++++++--
 2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/backend.c b/backend.c
index 38cc45b..4acac8e 100644
--- a/backend.c
+++ b/backend.c
@@ -56,13 +56,23 @@ memmap_chunk const *find_map_chunk(uint32_t address, cpu_options *opts, uint16_t
 	if (size_sum) {
 		*size_sum = 0;
 	}
+	uint32_t minsize;
+	if (flags == MMAP_CODE) {
+		minsize = 1 << (opts->ram_flags_shift + 3);
+	} else {
+		minsize = 0;
+	}
 	address &= opts->address_mask;
 	for (memmap_chunk const *cur = opts->memmap, *end = opts->memmap + opts->memmap_chunks; cur != end; cur++)
 	{
 		if (address >= cur->start && address < cur->end) {
 			return cur;
 		} else if (size_sum && (cur->flags & flags) == flags) {
-			*size_sum += chunk_size(opts, cur);
+			uint32_t size = chunk_size(opts, cur);
+			if (size < minsize) {
+				size = minsize;
+			}
+			*size_sum += size;
 		}
 	}
 	return NULL;
@@ -269,13 +279,15 @@ uint32_t chunk_size(cpu_options *opts, memmap_chunk const *chunk)
 uint32_t ram_size(cpu_options *opts)
 {
 	uint32_t size = 0;
+	uint32_t minsize = 1 << (opts->ram_flags_shift + 3);
 	for (int i = 0; i < opts->memmap_chunks; i++)
 	{
 		if (opts->memmap[i].flags & MMAP_CODE) {
-			if (opts->memmap[i].mask == opts->address_mask) {
-				size += opts->memmap[i].end - opts->memmap[i].start;
+			uint32_t cursize = chunk_size(opts, opts->memmap + i);
+			if (cursize < minsize) {
+				size += minsize;
 			} else {
-				size += opts->memmap[i].mask + 1;
+				size += cursize;
 			}
 		}
 	}
diff --git a/backend_x86.c b/backend_x86.c
index 9458499..20cb9d3 100644
--- a/backend_x86.c
+++ b/backend_x86.c
@@ -299,10 +299,16 @@ code_ptr gen_mem_fun(cpu_options * opts, memmap_chunk const * memmap, uint32_t n
 			retn(code);
 		}
 		if (memmap[chunk].flags & MMAP_CODE) {
+			uint32_t added_offset;
 			if (memmap[chunk].mask == opts->address_mask) {
-				ram_flags_off += (memmap[chunk].end - memmap[chunk].start) / (1 << opts->ram_flags_shift) / 8; ;
+				added_offset = (memmap[chunk].end - memmap[chunk].start) / (1 << opts->ram_flags_shift) / 8;
 			} else {
-				ram_flags_off += (memmap[chunk].mask + 1) /  (1 << opts->ram_flags_shift) / 8;;
+				added_offset = (memmap[chunk].mask + 1) /  (1 << opts->ram_flags_shift) / 8;
+			}
+			if (added_offset) {
+				ram_flags_off += added_offset;
+			} else {
+				ram_flags_off += 1;
 			}
 		}
 		if (lb_jcc) {
-- 
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