From 7dae81b2de3a20d5408c3c26324036de2c8a3a90 Mon Sep 17 00:00:00 2001
From: borutr <borutr@4a8a32a2-be11-0410-ad9d-d568d2c75423>
Date: Sun, 17 Feb 2008 12:30:30 +0000
Subject: [PATCH] * src/z80/gen.c, src/z80/peeph.def: applied patch   #1893510:
 Improve logical left shift on Z80, thanks to Philipp Krause

git-svn-id: https://sdcc.svn.sourceforge.net/svnroot/sdcc/trunk/sdcc@5016 4a8a32a2-be11-0410-ad9d-d568d2c75423
---
 ChangeLog         |  2 ++
 src/z80/gen.c     | 24 ++++++++++++++++++------
 src/z80/peeph.def | 16 ++++++++++++++++
 3 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 6f97c0c9..de698e3e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -8,6 +8,8 @@
 
 	* src/z80/peeph.def: applied patch
 	  #1893626: Optimize tail calls on Z80, thanks to Philipp Krause
+	* src/z80/gen.c, src/z80/peeph.def: applied patch
+	  #1893510: Improve logical left shift on Z80, thanks to Philipp Krause
 
 2008-02-16 Maarten Brock <sourceforge.brock AT dse.nl>
 
diff --git a/src/z80/gen.c b/src/z80/gen.c
index 697c3e09..db4dcf87 100644
--- a/src/z80/gen.c
+++ b/src/z80/gen.c
@@ -6010,13 +6010,25 @@ shiftL1Left2Result (operand * left, int offl,
                     operand * result, int offr, int shCount)
 {
   const char *l;
-  l = aopGet (AOP (left), offl, FALSE);
-  _moveA (l);
-  /* shift left accumulator */
-  AccLsh (shCount);
-  aopPut (AOP (result), "a", offr);
-}
 
+  /* If operand and result are the same we can shift in place.
+     However shifting in acc using add is cheaper than shifting
+     in place using sla; when shifting by more than 2 shifting in
+     acc is worth the additional effort for loading from/to acc. */
+  if (sameRegs (AOP (left), AOP (result)) && shCount <= 2 && offr == offl)
+    {
+      while (shCount--)
+        emit2 ("sla %s", aopGet (AOP (result), 0, FALSE));
+    }
+  else
+    {
+      l = aopGet (AOP (left), offl, FALSE);
+      _moveA (l);
+      /* shift left accumulator */
+      AccLsh (shCount);
+      aopPut (AOP (result), "a", offr);
+    }
+}
 
 /*-----------------------------------------------------------------*/
 /* genlshTwo - left shift two bytes by known amount                */
diff --git a/src/z80/peeph.def b/src/z80/peeph.def
index 90b1b2b1..02e485b7 100644
--- a/src/z80/peeph.def
+++ b/src/z80/peeph.def
@@ -456,6 +456,22 @@ replace restart {
 	ld	%1,a
 } if notVolatile(%1)
 
+// sdcc does not use the H flag. sla resets it, while add sets it.
+// To ensure that the state of the H flag is not changed by this
+// peephole uncomment the add %3, %4 at the end (since it overwrite the H flag).
+replace restart {
+	ld	%1, a
+	sla	%1
+	ld	a, %2
+	//add	%3, %4
+} by {
+	add	a, a
+	; peephole 42a shifts in accumulator insted of %1
+	ld	%1, a
+	ld	a, %2
+	//add	%3, %4
+}
+
 replace restart {
 	ld	%1,a
 	ld	a,%2
-- 
2.30.2