cmd/6l, cmd/8l: use one-byte XCHG forms when possible

Pointed out by khr.

R=ken2
CC=golang-dev
https://golang.org/cl/11145044

diff --git a/src/cmd/6l/optab.c b/src/cmd/6l/optab.c
index 5080dd7e90fd2572fec93bb0ec80df248ae2d6ba..da31672d3afa39ab81ecf50873f7b19040fcd830 100644 (file)
--- a/src/cmd/6l/optab.c
+++ b/src/cmd/6l/optab.c
@@ -247,8 +247,10 @@ uchar      yrb_mb[] =
        Yrb,    Ymb,    Zr_m,   1,
        0
 };
-uchar  yml_ml[] =
+uchar  yxchg[] =
 {
+       Yax,    Yrl,    Z_rp,   1,
+       Yrl,    Yax,    Zrp_,   1,
        Yrl,    Yml,    Zr_m,   1,
        Yml,    Yrl,    Zm_r,   1,
        0
@@ -1174,9 +1176,9 @@ Optab optab[] =
        { AWAIT,        ynone,  Px, 0x9b },
        { AWORD,        ybyte,  Px, 2 },
        { AXCHGB,       yml_mb, Pb, 0x86,0x86 },
-       { AXCHGL,       yml_ml, Px, 0x87,0x87 },
-       { AXCHGQ,       yml_ml, Pw, 0x87,0x87 },
-       { AXCHGW,       yml_ml, Pe, 0x87,0x87 },
+       { AXCHGL,       yxchg,  Px, 0x90,0x90,0x87,0x87 },
+       { AXCHGQ,       yxchg,  Pw, 0x90,0x90,0x87,0x87 },
+       { AXCHGW,       yxchg,  Pe, 0x90,0x90,0x87,0x87 },
        { AXLAT,        ynone,  Px, 0xd7 },
        { AXORB,        yxorb,  Pb, 0x34,0x80,(06),0x30,0x32 },
        { AXORL,        yxorl,  Px, 0x83,(06),0x35,0x81,(06),0x31,0x33 },

diff --git a/src/cmd/8l/optab.c b/src/cmd/8l/optab.c
index f7b44853d00193d7ed8d1a46ebe7dfebdc6fa55f..c024c19b35c5381a0afc486eb1bb31278594a54e 100644 (file)
--- a/src/cmd/8l/optab.c
+++ b/src/cmd/8l/optab.c
@@ -196,8 +196,10 @@ uchar      yml_mb[] =
        Ymb,    Yrb,    Zm_r,   1,
        0
 };
-uchar  yml_ml[] =
+uchar  yxchg[] =
 {
+       Yax,    Yrl,    Z_rp,   1,
+       Yrl,    Yax,    Zrp_,   1,
        Yrl,    Yml,    Zr_m,   1,
        Yml,    Yrl,    Zm_r,   1,
        0
@@ -696,8 +698,8 @@ Optab optab[] =
        { AWAIT,        ynone,  Px, 0x9b },
        { AWORD,        ybyte,  Px, 2 },
        { AXCHGB,       yml_mb, Pb, 0x86,0x86 },
-       { AXCHGL,       yml_ml, Px, 0x87,0x87 },
-       { AXCHGW,       yml_ml, Pe, 0x87,0x87 },
+       { AXCHGL,       yxchg,  Px, 0x90,0x90,0x87,0x87 },
+       { AXCHGW,       yxchg,  Pe, 0x90,0x90,0x87,0x87 },
        { AXLAT,        ynone,  Px, 0xd7 },
        { AXORB,        yxorb,  Pb, 0x34,0x80,(06),0x30,0x32 },
        { AXORL,        yxorl,  Px, 0x83,(06),0x35,0x81,(06),0x31,0x33 },