From 483edf69cdc738c2315040ff9f98e4f25afdf4ae Mon Sep 17 00:00:00 2001
From: Mark Wooding <mdw@distorted.org.uk>
Date: Wed, 14 Oct 2020 00:14:49 +0100
Subject: [PATCH] base/asm-common.h: Improve conditional instruction notation.

ARM64 conditional instructions -- `ccmp', `csel', etc. -- are
inexplicably notated differently from conditional branches.  The latter
are rather pleasantly written as `b.CC TARGET', while the former are,
disappointingly, `csel RD, RN, RM, CC' and similar, with the condition
tacked on the end.

Fix this by introducing aliases `csel.CC' and suchlike for all of the
conditional instructions.
---
 base/asm-common.h | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/base/asm-common.h b/base/asm-common.h
index ebcba2c6..18c61fc1 100644
--- a/base/asm-common.h
+++ b/base/asm-common.h
@@ -1114,6 +1114,54 @@ name:
 .macro	endprologue
 .endm
 
+// Notational improvement: write `csel.CC' etc., rather than `csel ..., CC'.
+#define _COND(_)							\
+	_(eq) _(ne) _(cs) _(cc) _(vs) _(vc) _(mi) _(pl)			\
+	_(ge) _(lt) _(gt) _(le) _(hi) _(ls) _(al) _(nv)			\
+	_(hs) _(lo)
+#define _INST(_)							\
+	_(ccmp) _(ccmn)							\
+	_(csel) 							\
+	_(csinc) _(cinc) _(cset)					\
+	_(csneg) _(cneg)						\
+	_(csinv) _(cinv) _(csetm)
+#define _CONDVAR(cc) _definstvar cc;
+#define _INSTVARS(inst)							\
+	.macro _definstvar cc;						\
+	  .macro inst.\cc args:vararg; inst \args, \cc; .endm;		\
+	.endm;								\
+	_COND(_CONDVAR);						\
+	.purgem _definstvar;
+	_INST(_INSTVARS)
+#undef _COND
+#undef _INST
+#undef _CONDVAR
+#undef _INSTVARS
+
+// Flag bits for `ccmp' and friends.
+#define CCMP_N 8
+#define CCMP_Z 4
+#define CCMP_C 2
+#define CCMP_V 1
+
+// Flag settings for satisfying conditions.
+#define CCMP_MI CCMP_N
+#define CCMP_PL 0
+#define CCMP_EQ CCMP_Z
+#define CCMP_NE 0
+#define CCMP_CS CCMP_C
+#define CCMP_HS CCMP_C
+#define CCMP_CC 0
+#define CCMP_LO 0
+#define CCMP_VS CCMP_V
+#define CCMP_VC 0
+#define CCMP_HI CCMP_C
+#define CCMP_LS 0
+#define CCMP_LT CCMP_N
+#define CCMP_GE 0
+#define CCMP_LE CCMP_N
+#define CCMP_GT 0
+
 #endif
 
 ///--------------------------------------------------------------------------
-- 
2.11.0