From: Mark Wooding <mdw@distorted.org.uk>
Date: Tue, 13 Oct 2020 23:15:17 +0000 (+0100)
Subject: base/asm-common.h, ...: Add missing `cmov' instruction (and `.CC' variants).
X-Git-Url: https://git.distorted.org.uk/~mdw/catacomb/commitdiff_plain/5f49478bd78e79bedb811e93f1f8feea83fc2979

base/asm-common.h, ...: Add missing `cmov' instruction (and `.CC' variants).

This instruction conditionally moves a value from one register to
another, otherwise leaving the destination unchanged:

	cmov RD, RN, CC == csel RD, RN, RD, CC

Also define `cmov.CC' for all condition codes CC.

Use this to slightly improve `rijndael_setup_arm64_crypto'.
---

diff --git a/base/asm-common.h b/base/asm-common.h
index 18c61fc1..323f2e8f 100644
--- a/base/asm-common.h
+++ b/base/asm-common.h
@@ -1114,6 +1114,11 @@ name:
 .macro	endprologue
 .endm
 
+// cmov RD, RN, CC: set RD to RN if CC is satisfied, otherwise do nothing
+.macro	cmov	rd, rn, cc
+	csel	\rd, \rn, \rd, \cc
+.endm
+
 // Notational improvement: write `csel.CC' etc., rather than `csel ..., CC'.
 #define _COND(_)							\
 	_(eq) _(ne) _(cs) _(cc) _(vs) _(vc) _(mi) _(pl)			\
@@ -1121,7 +1126,7 @@ name:
 	_(hs) _(lo)
 #define _INST(_)							\
 	_(ccmp) _(ccmn)							\
-	_(csel) 							\
+	_(csel) _(cmov)							\
 	_(csinc) _(cinc) _(cset)					\
 	_(csneg) _(cneg)						\
 	_(csinv) _(cinv) _(csetm)
diff --git a/symm/rijndael-arm64-crypto.S b/symm/rijndael-arm64-crypto.S
index 98f61734..df0bb9d9 100644
--- a/symm/rijndael-arm64-crypto.S
+++ b/symm/rijndael-arm64-crypto.S
@@ -131,7 +131,7 @@ FUNC(rijndael_setup_arm64_crypto)
 	sub	x6, x6, #1
 	cmp	x8, x3
 	cbz	x6, 9f
-	csel	x8, x8, xzr, cc
+	cmov.cs	x8, xzr
 	b	0b
 
 	// Next job is to construct the decryption keys.  The keys for the