From: Matthew Dempsky <mdempsky@google.com>
Date: Fri, 18 Jan 2013 22:29:53 +0000 (-0500)
Subject: cmd/6c: Optimize rotate expressions to use rotate instructions.
X-Git-Tag: go1.1rc2~1346
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=bb192d13996abdeeec86cf756f8176a42e5c2672;p=gostls13.git

cmd/6c: Optimize rotate expressions to use rotate instructions.

For simplicity, only recognizes expressions of the exact form
"(x << a) | (x >> b)" where x is a variable and a and b are
integer constant expressions that add to x's bit width.

Fixes #4629.

$ cat rotate.c
unsigned int
rotate(unsigned int x)
{
        x = (x << 3) | (x >> (sizeof(x) * 8 - 3));
        return x;
}

## BEFORE
$ go tool 6c -S rotate.c
(rotate.c:2)	TEXT	rotate+0(SB),$0-8
(rotate.c:2)	MOVL	x+0(FP),!!DX
(rotate.c:4)	MOVL	DX,!!AX
(rotate.c:4)	SALL	$3,!!AX
(rotate.c:4)	MOVL	DX,!!CX
(rotate.c:4)	SHRL	$29,!!CX
(rotate.c:4)	ORL	CX,!!AX
(rotate.c:5)	RET	,!!
(rotate.c:5)	RET	,!!
(rotate.c:5)	END	,!!

## AFTER
$ go tool 6c -S rotate.c
(rotate.c:2)	TEXT	rotate+0(SB),$0-8
(rotate.c:4)	MOVL	x+0(FP),!!AX
(rotate.c:4)	ROLL	$3,!!AX
(rotate.c:5)	RET	,!!
(rotate.c:5)	RET	,!!
(rotate.c:5)	END	,!!

R=rsc, minux.ma
CC=golang-dev
https://golang.org/cl/7069056
---

diff --git a/src/cmd/6c/cgen.c b/src/cmd/6c/cgen.c
index 1fe0156c64..95400c4453 100644
--- a/src/cmd/6c/cgen.c
+++ b/src/cmd/6c/cgen.c
@@ -265,6 +265,18 @@ cgen(Node *n, Node *nn)
 				break;
 			}
 		}
+		if(n->op == OOR && l->op == OASHL && r->op == OLSHR
+		&& l->right->op == OCONST && r->right->op == OCONST
+		&& l->left->op == ONAME && r->left->op == ONAME
+		&& l->left->sym == r->left->sym
+		&& l->right->vconst + r->right->vconst == 8 * l->left->type->width) {
+			regalloc(&nod, l->left, nn);
+			cgen(l->left, &nod);
+			gopcode(OROTL, n->type, l->right, &nod);
+			gmove(&nod, nn);
+			regfree(&nod);
+			break;
+		}
 		if(n->op == OADD && l->op == OASHL && l->right->op == OCONST
 		&& (r->op != OCONST || r->vconst < -128 || r->vconst > 127)) {
 			c = l->right->vconst;
diff --git a/src/cmd/6c/txt.c b/src/cmd/6c/txt.c
index fcc97ee6ec..364b189f27 100644
--- a/src/cmd/6c/txt.c
+++ b/src/cmd/6c/txt.c
@@ -1360,6 +1360,16 @@ gopcode(int o, Type *ty, Node *f, Node *t)
 			a = ASALQ;
 		break;
 
+	case OROTL:
+		a = AROLL;
+		if(et == TCHAR || et == TUCHAR)
+			a = AROLB;
+		if(et == TSHORT || et == TUSHORT)
+			a = AROLW;
+		if(et == TVLONG || et == TUVLONG || et == TIND)
+			a = AROLQ;
+		break;
+
 	case OFUNC:
 		a = ACALL;
 		break;
diff --git a/src/cmd/8c/cgen.c b/src/cmd/8c/cgen.c
index 7a49b671ca..78eb7ecedb 100644
--- a/src/cmd/8c/cgen.c
+++ b/src/cmd/8c/cgen.c
@@ -277,6 +277,18 @@ cgen(Node *n, Node *nn)
 				break;
 			}
 		}
+		if(n->op == OOR && l->op == OASHL && r->op == OLSHR
+		&& l->right->op == OCONST && r->right->op == OCONST
+		&& l->left->op == ONAME && r->left->op == ONAME
+		&& l->left->sym == r->left->sym
+		&& l->right->vconst + r->right->vconst == 8 * l->left->type->width) {
+			regalloc(&nod, l->left, nn);
+			cgen(l->left, &nod);
+			gopcode(OROTL, n->type, l->right, &nod);
+			gmove(&nod, nn);
+			regfree(&nod);
+			break;
+		}
 		if(n->op == OADD && l->op == OASHL && l->right->op == OCONST
 		&& (r->op != OCONST || r->vconst < -128 || r->vconst > 127)) {
 			c = l->right->vconst;
diff --git a/src/cmd/8c/txt.c b/src/cmd/8c/txt.c
index d229462da3..d7873e3855 100644
--- a/src/cmd/8c/txt.c
+++ b/src/cmd/8c/txt.c
@@ -1253,6 +1253,14 @@ gopcode(int o, Type *ty, Node *f, Node *t)
 			a = ASALW;
 		break;
 
+	case OROTL:
+		a = AROLL;
+		if(et == TCHAR || et == TUCHAR)
+			a = AROLB;
+		if(et == TSHORT || et == TUSHORT)
+			a = AROLW;
+		break;
+
 	case OFUNC:
 		a = ACALL;
 		break;
diff --git a/src/cmd/cc/cc.h b/src/cmd/cc/cc.h
index 6153bf9f75..f9e1546ca3 100644
--- a/src/cmd/cc/cc.h
+++ b/src/cmd/cc/cc.h
@@ -325,6 +325,7 @@ enum
 	OINDEX,
 	OFAS,
 	OREGPAIR,
+	OROTL,
 
 	OEND
 };
diff --git a/src/cmd/cc/sub.c b/src/cmd/cc/sub.c
index 9f124cb820..3a55763859 100644
--- a/src/cmd/cc/sub.c
+++ b/src/cmd/cc/sub.c
@@ -1515,6 +1515,7 @@ Init	onamesinit[] =
 	OINDEX,		0,	"INDEX",
 	OFAS,		0,	"FAS",
 	OREGPAIR,	0,	"REGPAIR",
+	OROTL,		0,	"ROTL",
 	OEND,		0,	"END",
 	-1,		0,	0,
 };