from /n/sources/patch/0l-fix-float; author lunaria21@gmail.com

this patch is to fix two issues about floating point in
0l/vl in little endian mode.

1. fix floating point register ordering in MOVD. the
least significant bits should be held in even numbered
fp register, regardless of the endianess. in LE mode it
is the first 4 bytes hold them, which is different from
BE.

2. 0l/vl outputs wrong bits for single precision floats
in little endian mode. this patch fixes it by using
fnuxi4 instead of fnuxi8. the debug output is added as
well. cf. inferno's 0l.

both are tested on loongson 2E machine, seems okay.

Reference: /n/atom/patch/applied/mipslefloat
Date: Wed Feb 19 04:02:33 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/vl/asm.c	Wed Feb 19 04:02:02 2014
+++ /sys/src/cmd/vl/asm.c	Wed Feb 19 04:02:04 2014
@@ -669,7 +669,7 @@
 				fl = ieeedtof(p->to.ieee);
 				cast = (char*)&fl;
 				for(; i<c; i++) {
-					buf.dbuf[l] = cast[fnuxi8[i+4]];
+					buf.dbuf[l] = cast[fnuxi4[i]];
 					l++;
 				}
 				break;
@@ -1019,8 +1019,13 @@
 			o1 = OP_IRR(opirr(ALAST), v>>16, REGZERO, REGTMP);
 			o2 = OP_IRR(opirr(AOR), v, REGTMP, REGTMP);
 			o3 = OP_RRR(oprrr(AADDU), r, REGTMP, REGTMP);
-			o4 = OP_IRR(opirr(AMOVF+ALAST), 0, REGTMP, p->to.reg+1);
-			o5 = OP_IRR(opirr(AMOVF+ALAST), 4, REGTMP, p->to.reg);
+			if(little) {
+				o4 = OP_IRR(opirr(AMOVF+ALAST), 0, REGTMP, p->to.reg);
+				o5 = OP_IRR(opirr(AMOVF+ALAST), 4, REGTMP, p->to.reg+1);
+			} else {
+				o4 = OP_IRR(opirr(AMOVF+ALAST), 0, REGTMP, p->to.reg+1);
+				o5 = OP_IRR(opirr(AMOVF+ALAST), 4, REGTMP, p->to.reg);
+			}
 			break;
 		case 16:
 			o1 = OP_IRR(opirr(ALAST), v>>16, REGZERO, REGTMP);
@@ -1029,8 +1034,13 @@
 			o4 = OP_IRR(opirr(AMOVF+ALAST), 0, REGTMP, p->to.reg);
 			break;
 		case 8:
-			o1 = OP_IRR(opirr(AMOVF+ALAST), v, r, p->to.reg+1);
-			o2 = OP_IRR(opirr(AMOVF+ALAST), v+4, r, p->to.reg);
+			if(little) {
+				o1 = OP_IRR(opirr(AMOVF+ALAST), v, r, p->to.reg);
+				o2 = OP_IRR(opirr(AMOVF+ALAST), v+4, r, p->to.reg+1);
+			} else {
+				o1 = OP_IRR(opirr(AMOVF+ALAST), v, r, p->to.reg+1);
+				o2 = OP_IRR(opirr(AMOVF+ALAST), v+4, r, p->to.reg);
+			}
 			break;
 		case 4:
 			o1 = OP_IRR(opirr(AMOVF+ALAST), v, r, p->to.reg);
@@ -1050,8 +1060,13 @@
 			o1 = OP_IRR(opirr(ALAST), v>>16, REGZERO, REGTMP);
 			o2 = OP_IRR(opirr(AOR), v, REGTMP, REGTMP);
 			o3 = OP_RRR(oprrr(AADDU), r, REGTMP, REGTMP);
-			o4 = OP_IRR(opirr(AMOVF), 0, REGTMP, p->from.reg+1);
-			o5 = OP_IRR(opirr(AMOVF), 4, REGTMP, p->from.reg);
+			if(little) {
+				o4 = OP_IRR(opirr(AMOVF), 0, REGTMP, p->from.reg);
+				o5 = OP_IRR(opirr(AMOVF), 4, REGTMP, p->from.reg+1);
+			} else {
+				o4 = OP_IRR(opirr(AMOVF), 0, REGTMP, p->from.reg+1);
+				o5 = OP_IRR(opirr(AMOVF), 4, REGTMP, p->from.reg);
+			}
 			break;
 		case 16:
 			if(r == REGTMP)
@@ -1062,8 +1077,13 @@
 			o4 = OP_IRR(opirr(AMOVF), 0, REGTMP, p->from.reg);
 			break;
 		case 8:
-			o1 = OP_IRR(opirr(AMOVF), v, r, p->from.reg+1);
-			o2 = OP_IRR(opirr(AMOVF), v+4, r, p->from.reg);
+			if(little) {
+				o1 = OP_IRR(opirr(AMOVF), v, r, p->from.reg);
+				o2 = OP_IRR(opirr(AMOVF), v+4, r, p->from.reg+1);
+			} else {
+				o1 = OP_IRR(opirr(AMOVF), v, r, p->from.reg+1);
+				o2 = OP_IRR(opirr(AMOVF), v+4, r, p->from.reg);
+			}
 			break;
 		case 4:
 			o1 = OP_IRR(opirr(AMOVF), v, r, p->from.reg);
--- /sys/src/cmd/vl/noop.c	Wed Feb 19 04:02:05 2014
+++ /sys/src/cmd/vl/noop.c	Wed Feb 19 04:02:06 2014
@@ -7,7 +7,7 @@
  * and "{ echo moon; echo plot } | scat".
  */
 enum {
-	Mips24k	= 0,
+	Mips24k	= 1,
 };
 
 static int
--- /sys/src/cmd/vl/obj.c	Wed Feb 19 04:02:08 2014
+++ /sys/src/cmd/vl/obj.c	Wed Feb 19 04:02:10 2014
@@ -1332,6 +1332,7 @@
 			if(i >= 3)
 				inuxi1[i-3] = c;
 			inuxi4[i] = c;
+			fnuxi4[i] = c;
 			fnuxi8[i] = c+4;
 			fnuxi8[i+4] = c;
 		} else {			/* oddball little-endian case */
@@ -1356,6 +1357,9 @@
 		for(i=0; i<4; i++)
 			Bprint(&bso, "%d", inuxi4[i]);
 		Bprint(&bso, "\nfnuxi = ");
+		for(i=0; i<4; i++)
+			Bprint(&bso, "%d", fnuxi4[i]);
+		Bprint(&bso, " ");
 		for(i=0; i<8; i++)
 			Bprint(&bso, "%d", fnuxi8[i]);
 		Bprint(&bso, "\n");