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 8b82adbf56c39111cadb5fca08ba0ae9100a5c90..1991c0c3529f3e5d1dd3e86bb4c7fef3d49f61c1 100644 (file)
--- 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 996128f75f3fe9912f10e7b578a808c5fc10c3d7..bbea92560e6b138fa035eeb2d6690a7b615c5903 100644 (file)
--- 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 2cb8c158519b2efdf65bf054fd1361d54a0fd181..605ed3786a0095f35c7a8150eb18d60dc1e0f669 100644 (file)
--- 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 ededcf67327d06c21944767b186e8f6641bf269b..fb312126b704acc9b142f1aa305369458a9a765a 100644 (file)
--- 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 3710033b20dcd273b6d8a3709a4aa0bcbf22679c..a4d9b8edab4c1c7dba3512e7eeac578509d961c1 100644 (file)
--- 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 bed9f8da68bd9c4ec55af8644cc0340315898e06..e8259c476d97e4f383e28c10910ecac03fc0f837 100644 (file)
--- 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 b1ef050d9e177eca94166d78be751c3a052c463c..97f5fbf7bce41508c28ae99d03e70a54ad332cfa 100644 (file)
--- 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 f09f3d34143e93fc71edf8347bd9ec952380a504..747e8083390fe83d4b2e3c5f6e98cb5efecb7e4b 100644 (file)
--- 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