From a66c85675226c82d1ec0e9cf22fdcff552e406d7 Mon Sep 17 00:00:00 2001
From: Andrew Chambers <ac@acha.ninja>
Date: Thu, 14 Oct 2021 22:39:39 +1300
Subject: Use short address displacement when possible.

---
 main.c       |  4 ++--
 test/test.sh | 16 +++++++++++++++-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/main.c b/main.c
index dd3c3db..1d88fe8 100644
--- a/main.c
+++ b/main.c
@@ -372,11 +372,11 @@ static void assemblemem(const Memarg *memarg, uint8_t rexw, VarBytes prefix,
   base = rm;
   rm = 4;
 
-  // TODO: if our disp fits in a +disp8, use that instead.
   if (memarg->disp.c == 0 && memarg->disp.l == 0 && ((base & 7) != 5)) {
     mod = 0; /* +0 */
   } else {
-    if (memarg->disp.c == 0 && memarg->disp.l == 0) {
+    if (memarg->disp.l == NULL && memarg->disp.c >= -128 &&
+        memarg->disp.c <= 127) {
       mod = 1; /* +disp8 */
     } else {
       mod = 2; /* +disp32 */
diff --git a/test/test.sh b/test/test.sh
index 08db8b8..9734915 100644
--- a/test/test.sh
+++ b/test/test.sh
@@ -144,6 +144,11 @@ do
   t "lea (%rsp), %r${r}x"
   t "lea (%rbp), %r${r}x"
   t "lea (%r${r}x), %r${r}x"
+  t "lea 1(%rsp), %r${r}x"
+  t "lea 127(%rsp), %r${r}x"
+  t "lea 128(%rsp), %r${r}x"
+  t "lea -129(%rsp), %r${r}x"
+  t "lea -127(%rsp), %r${r}x"
   t "lea 2147483647(%rsp), %r${r}x"
   t "lea 2147483647(%rbp), %r${r}x"
   t "lea 2147483647(%r${r}x), %r${r}x"
@@ -152,6 +157,11 @@ do
   t "lea (%rsp, %r${r}x), %r${r}x"
   t "lea (%rbp, %r${r}x), %r${r}x"
   t "lea (%r${r}x, %r${r}x), %r${r}x"
+  t "lea 1(%rsp, %r${r}x), %r${r}x"
+  t "lea 127(%rbp, %r${r}x), %r${r}x"
+  t "lea 128(%rbp, %r${r}x), %r${r}x"
+  t "lea -129(%rbp, %r${r}x), %r${r}x"
+  t "lea -127(%r${r}x, %r${r}x), %r${r}x"
   t "lea 2147483647(%rsp, %r${r}x), %r${r}x"
   t "lea 2147483647(%rbp, %r${r}x), %r${r}x"
   t "lea 2147483647(%r${r}x, %r${r}x), %r${r}x"
@@ -159,6 +169,11 @@ do
   t "lea (%rsp, %r${r}x, 4), %r${r}x"
   t "lea (%rbp, %r${r}x, 4), %r${r}x"
   t "lea (%r${r}x, %r${r}x, 4), %r${r}x"
+  t "lea 1(%rsp, %r${r}x, 4), %r${r}x"
+  t "lea 127(%rbp, %r${r}x, 4), %r${r}x"
+  t "lea 128(%r${r}x, %r${r}x, 4), %r${r}x"
+  t "lea -129(%r${r}x, %r${r}x, 4), %r${r}x"
+  t "lea -127(%r${r}x, %r${r}x, 4), %r${r}x"
   t "lea 2147483647(%rsp, %r${r}x, 4), %r${r}x"
   t "lea 2147483647(%rbp, %r${r}x, 4), %r${r}x"
   t "lea 2147483647(%r${r}x, %r${r}x, 4), %r${r}x"
@@ -181,7 +196,6 @@ for cc in $conditioncodes
 do
   t "set${cc} %al"
   t "set${cc} (%rax)"
-  t "j${cc} $0xefffffff"
 done
 
 for op in sal sar shl shr
-- 
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