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Save regs correctly around rep movs

--- a/6/insns.def

+++ b/6/insns.def

@@ -55,22 +55,22 @@

     "\trep movsb\n",

     "\tREP; MOVSB\n",

     Use(.r={Rrcx,Rrsi,Rrdi}),

-    Def(None))

+    Def(.r={Rrcx,Rrsi,Rrdi}))

 Insn(Irepmovsw,

     "\trep movsw\n",

     "\tREP; MOVSW\n",

     Use(.r={Rrcx,Rrsi,Rrdi}),

-    Def(None))

+    Def(.r={Rrcx,Rrsi,Rrdi}))

 Insn(Irepmovsl,

     "\trep movsl\n",

     "\tREP; MOVSL\n",

     Use(.r={Rrcx,Rrsi,Rrdi}),

-    Def(None))

+    Def(.r={Rrcx,Rrsi,Rrdi}))

 Insn(Irepmovsq,

     "\trep movsq\n",

     "\tREP; MOVSQ\n",

     Use(.r={Rrcx,Rrsi,Rrdi}),

-    Def(None))

+    Def(.r={Rrcx,Rrsi,Rrdi}))

 Insn(Ilea,

     "\tlea%2t %m,%r\n",

     "\tLEA%2T %M,%R\n",

--- a/6/isel.c

+++ b/6/isel.c

@@ -405,6 +405,7 @@

 static void blit(Isel *s, Loc *to, Loc *from, size_t dstoff, size_t srcoff, size_t sz, size_t align)

 {

 	size_t i, modesz;

+	Loc *savsi, *savdi, *savcx; /* pointers to src, dst */

 	Loc *sp, *dp, *len; /* pointers to src, dst */

 	Loc *tmp, *src, *dst; /* source memory, dst memory */

@@ -429,7 +430,13 @@

 			}

 		}

 	} else {

+		savsi = locreg(ModeQ);

+		savdi = locreg(ModeQ);

+		savcx = locreg(ModeQ);

 		len = loclit(sz, ModeQ);

+		g(s, Imov, locphysreg(Rrsi), savsi);

+		g(s, Imov, locphysreg(Rrdi), savdi);

+		g(s, Imov, locphysreg(Rrcx), savcx);

 		sp = newr(s, from);

 		dp = newr(s, to);

@@ -446,6 +453,9 @@

 		else

 			g(s, Imov, dp, locphysreg(Rrdi), NULL);

 		g(s, Irepmovsb, NULL);

+		g(s, Imov, savsi, locphysreg(Rrsi));

+		g(s, Imov, savdi, locphysreg(Rrdi));

+		g(s, Imov, savcx, locphysreg(Rrcx));

 	}

 }