From: Russ Cox <rsc@golang.org>
Date: Tue, 10 Apr 2012 16:51:59 +0000 (-0400)
Subject: 6c, 6g, 6l: add MOVQL to make truncation explicit
X-Git-Tag: go1.1rc2~3407
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=e530d6a1e00fbc0149b71bca9f940058838c1c44;p=gostls13.git

6c, 6g, 6l: add MOVQL to make truncation explicit

Without an explicit signal for a truncation, copy propagation
will sometimes propagate a 32-bit truncation and end up
overwriting uses of the original 64-bit value.

The case that arose in practice is in C but I believe
that the same could plausibly happen in Go.
The main reason we didn't run into the same in Go
is that I (perhaps incorrectly?) drop MOVL AX, AX
during gins, so the truncation was never generated, so
it didn't confuse the optimizer.

Fixes #1315.
Fixes #3488.

R=ken2
CC=golang-dev
https://golang.org/cl/6002043
---

diff --git a/src/cmd/6c/peep.c b/src/cmd/6c/peep.c
index 8b82adbf56..1991c0c352 100644
--- a/src/cmd/6c/peep.c
+++ b/src/cmd/6c/peep.c
@@ -383,6 +383,7 @@ subprop(Reg *r0)
 		case AMOVSB:
 		case AMOVSL:
 		case AMOVSQ:
+		case AMOVQL:
 			return 0;
 
 		case AMOVL:
@@ -581,6 +582,7 @@ copyu(Prog *p, Adr *v, Adr *s)
 	case AMOVWLZX:
 	case AMOVWQSX:
 	case AMOVWQZX:
+	case AMOVQL:
 
 	case AMOVSS:
 	case AMOVSD:
diff --git a/src/cmd/6c/reg.c b/src/cmd/6c/reg.c
index 996128f75f..bbea92560e 100644
--- a/src/cmd/6c/reg.c
+++ b/src/cmd/6c/reg.c
@@ -211,6 +211,7 @@ regopt(Prog *p)
 		case AMOVWLZX:
 		case AMOVWQSX:
 		case AMOVWQZX:
+		case AMOVQL:
 
 		case AMOVSS:
 		case AMOVSD:
diff --git a/src/cmd/6c/txt.c b/src/cmd/6c/txt.c
index 2cb8c15851..605ed3786a 100644
--- a/src/cmd/6c/txt.c
+++ b/src/cmd/6c/txt.c
@@ -809,7 +809,6 @@ gmove(Node *f, Node *t)
 	case CASE(	TUINT,	TCHAR):
 	case CASE(	TLONG,	TCHAR):
 	case CASE(	TULONG,	TCHAR):
-	case CASE(	TIND,	TCHAR):
 
 	case CASE(	TCHAR,	TUCHAR):
 	case CASE(	TUCHAR,	TUCHAR):
@@ -819,7 +818,6 @@ gmove(Node *f, Node *t)
 	case CASE(	TUINT,	TUCHAR):
 	case CASE(	TLONG,	TUCHAR):
 	case CASE(	TULONG,	TUCHAR):
-	case CASE(	TIND,	TUCHAR):
 
 	case CASE(	TSHORT,	TSHORT):
 	case CASE(	TUSHORT,TSHORT):
@@ -827,7 +825,6 @@ gmove(Node *f, Node *t)
 	case CASE(	TUINT,	TSHORT):
 	case CASE(	TLONG,	TSHORT):
 	case CASE(	TULONG,	TSHORT):
-	case CASE(	TIND,	TSHORT):
 
 	case CASE(	TSHORT,	TUSHORT):
 	case CASE(	TUSHORT,TUSHORT):
@@ -835,42 +832,26 @@ gmove(Node *f, Node *t)
 	case CASE(	TUINT,	TUSHORT):
 	case CASE(	TLONG,	TUSHORT):
 	case CASE(	TULONG,	TUSHORT):
-	case CASE(	TIND,	TUSHORT):
 
 	case CASE(	TINT,	TINT):
 	case CASE(	TUINT,	TINT):
 	case CASE(	TLONG,	TINT):
 	case CASE(	TULONG,	TINT):
-	case CASE(	TIND,	TINT):
 
 	case CASE(	TINT,	TUINT):
 	case CASE(	TUINT,	TUINT):
 	case CASE(	TLONG,	TUINT):
 	case CASE(	TULONG,	TUINT):
-	case CASE(	TIND,	TUINT):
-
-	case CASE(	TUINT,	TIND):
-	case CASE(	TVLONG,	TUINT):
-	case CASE(	TVLONG,	TULONG):
-	case CASE(	TUVLONG, TUINT):
-	case CASE(	TUVLONG, TULONG):
  *****/
 		a = AMOVL;
 		break;
 
-	case CASE(	TVLONG,	TCHAR):
-	case	CASE(	TVLONG,	TSHORT):
-	case CASE(	TVLONG,	TINT):
-	case CASE(	TVLONG,	TLONG):
-	case CASE(	TUVLONG, TCHAR):
-	case	CASE(	TUVLONG, TSHORT):
-	case CASE(	TUVLONG, TINT):
-	case CASE(	TUVLONG, TLONG):
+	case CASE(	TINT,	TIND):
 	case CASE(	TINT,	TVLONG):
 	case CASE(	TINT,	TUVLONG):
-	case CASE(	TLONG,	TVLONG):
-	case CASE(	TINT,	TIND):
 	case CASE(	TLONG,	TIND):
+	case CASE(	TLONG,	TVLONG):
+	case CASE(	TLONG,	TUVLONG):
 		a = AMOVLQSX;
 		if(f->op == OCONST) {
 			f->vconst &= (uvlong)0xffffffffU;
@@ -886,22 +867,53 @@ gmove(Node *f, Node *t)
 	case CASE(	TULONG,	TVLONG):
 	case CASE(	TULONG,	TUVLONG):
 	case CASE(	TULONG,	TIND):
-		a = AMOVL;	/* same effect as AMOVLQZX */
+		a = AMOVLQZX;
 		if(f->op == OCONST) {
 			f->vconst &= (uvlong)0xffffffffU;
 			a = AMOVQ;
 		}
 		break;
+	
+	case CASE(	TIND,	TCHAR):
+	case CASE(	TIND,	TUCHAR):
+	case CASE(	TIND,	TSHORT):
+	case CASE(	TIND,	TUSHORT):
+	case CASE(	TIND,	TINT):
+	case CASE(	TIND,	TUINT):
+	case CASE(	TIND,	TLONG):
+	case CASE(	TIND,	TULONG):
+	case CASE(	TVLONG,	TCHAR):
+	case CASE(	TVLONG,	TUCHAR):
+	case CASE(	TVLONG,	TSHORT):
+	case CASE(	TVLONG,	TUSHORT):
+	case CASE(	TVLONG,	TINT):
+	case CASE(	TVLONG,	TUINT):
+	case CASE(	TVLONG,	TLONG):
+	case CASE(	TVLONG,	TULONG):
+	case CASE(	TUVLONG,	TCHAR):
+	case CASE(	TUVLONG,	TUCHAR):
+	case CASE(	TUVLONG,	TSHORT):
+	case CASE(	TUVLONG,	TUSHORT):
+	case CASE(	TUVLONG,	TINT):
+	case CASE(	TUVLONG,	TUINT):
+	case CASE(	TUVLONG,	TLONG):
+	case CASE(	TUVLONG,	TULONG):
+		a = AMOVQL;
+		if(f->op == OCONST) {
+			f->vconst &= (int)0xffffffffU;
+			a = AMOVL;
+		}
+		break;	
 
+	case CASE(	TIND,	TIND):
 	case CASE(	TIND,	TVLONG):
-	case CASE(	TVLONG,	TVLONG):
-	case CASE(	TUVLONG,	TVLONG):
-	case CASE(	TVLONG,	TUVLONG):
-	case CASE(	TUVLONG,	TUVLONG):
 	case CASE(	TIND,	TUVLONG):
 	case CASE(	TVLONG,	TIND):
+	case CASE(	TVLONG,	TVLONG):
+	case CASE(	TVLONG,	TUVLONG):
 	case CASE(	TUVLONG,	TIND):
-	case CASE(	TIND,	TIND):
+	case CASE(	TUVLONG,	TVLONG):
+	case CASE(	TUVLONG,	TUVLONG):
 		a = AMOVQ;
 		break;
 
diff --git a/src/cmd/6g/gsubr.c b/src/cmd/6g/gsubr.c
index ededcf6732..fb312126b7 100644
--- a/src/cmd/6g/gsubr.c
+++ b/src/cmd/6g/gsubr.c
@@ -706,11 +706,14 @@ gmove(Node *f, Node *t)
 	case CASE(TINT32, TUINT32):
 	case CASE(TUINT32, TINT32):
 	case CASE(TUINT32, TUINT32):
+		a = AMOVL;
+		break;
+
 	case CASE(TINT64, TINT32):	// truncate
 	case CASE(TUINT64, TINT32):
 	case CASE(TINT64, TUINT32):
 	case CASE(TUINT64, TUINT32):
-		a = AMOVL;
+		a = AMOVQL;
 		break;
 
 	case CASE(TINT64, TINT64):	// same size
diff --git a/src/cmd/6g/peep.c b/src/cmd/6g/peep.c
index 3710033b20..a4d9b8edab 100644
--- a/src/cmd/6g/peep.c
+++ b/src/cmd/6g/peep.c
@@ -200,6 +200,7 @@ loop1:
 		case AMOVWQZX:
 		case AMOVLQSX:
 		case AMOVLQZX:
+		case AMOVQL:
 			if(regtyp(&p->to)) {
 				r1 = rnops(uniqs(r));
 				if(r1 != R) {
@@ -636,6 +637,7 @@ copyu(Prog *p, Adr *v, Adr *s)
 	case AMOVWLZX:
 	case AMOVWQSX:
 	case AMOVWQZX:
+	case AMOVQL:
 
 	case AMOVSS:
 	case AMOVSD:
diff --git a/src/cmd/6g/reg.c b/src/cmd/6g/reg.c
index bed9f8da68..e8259c476d 100644
--- a/src/cmd/6g/reg.c
+++ b/src/cmd/6g/reg.c
@@ -326,6 +326,7 @@ regopt(Prog *firstp)
 		case AMOVWLZX:
 		case AMOVWQSX:
 		case AMOVWQZX:
+		case AMOVQL:
 		case APOPQ:
 
 		case AMOVSS:
diff --git a/src/cmd/6l/6.out.h b/src/cmd/6l/6.out.h
index b1ef050d9e..97f5fbf7bc 100644
--- a/src/cmd/6l/6.out.h
+++ b/src/cmd/6l/6.out.h
@@ -741,6 +741,8 @@ enum	as
 	APREFETCHT1,
 	APREFETCHT2,
 	APREFETCHNTA,
+	
+	AMOVQL,
 
 	ALAST
 };
diff --git a/src/cmd/6l/optab.c b/src/cmd/6l/optab.c
index f09f3d3414..747e808339 100644
--- a/src/cmd/6l/optab.c
+++ b/src/cmd/6l/optab.c
@@ -1282,6 +1282,8 @@ Optab optab[] =
 	{ APREFETCHT1,	yprefetch,	Pm,	0x18,(02) },
 	{ APREFETCHT2,	yprefetch,	Pm,	0x18,(03) },
 	{ APREFETCHNTA,	yprefetch,	Pm,	0x18,(00) },
+	
+	{ AMOVQL,	yrl_ml,	Px, 0x89 },
 
 	{ AEND },
 	0