cmd/internal/obj/x86: change SHRQ to store second source in From3, not jammed into...

SHRQ CX, DX:AX is changing to SHRQ CX, AX, DX.
This is the first step: using SHRQ From=CX, From3=AX, To=DX
as the preferred encoding.
Once the assemblers and 6g have been updated,
support for the old encoding can be removed.

Change-Id: Ie603fb8ac25a6df78e42f7ddcae078a7684a7c26
Reviewed-on: https://go-review.googlesource.com/6693
Reviewed-by: Rob Pike <r@golang.org>

diff --git a/src/cmd/internal/obj/x86/asm6.go b/src/cmd/internal/obj/x86/asm6.go
index ee73fb9717dc8d9d18e546d60b4e35238768ab2c..7230ae86ae8640aad778dadb6a5e8b8b4dac58f3 100644 (file)
--- a/src/cmd/internal/obj/x86/asm6.go
+++ b/src/cmd/internal/obj/x86/asm6.go
@@ -69,7 +69,7 @@ type Movtab struct {
 }
 
 const (
-       Yxxx = 0 + iota
+       Yxxx = iota
        Ynone
        Yi0
        Yi1
@@ -91,7 +91,6 @@ const (
        Yml
        Ym
        Ybr
-       Ycol
        Ycs
        Yss
        Yds
@@ -136,8 +135,12 @@ const (
        Yxm
        Ytls
        Ytextsize
+       Yreg2
        Ymax
-       Zxxx = 0 + iota - 68
+)
+
+const (
+       Zxxx = iota
        Zlit
        Zlitm_r
        Z_rp
@@ -183,6 +186,9 @@ const (
        Zclr
        Zbyte
        Zmax
+)
+
+const (
        Px     = 0
        P32    = 0x32
        Pe     = 0x66
@@ -1908,9 +1914,27 @@ func oclass(ctxt *obj.Link, p *obj.Prog, a *obj.Addr) int {
        // TODO(rsc): This special case is for SHRQ $3, AX:DX,
        // which encodes as SHRQ $32(DX*0), AX.
        // Similarly SHRQ CX, AX:DX is really SHRQ CX(DX*0), AX.
-       // Change encoding and remove.
-       if (a.Type == obj.TYPE_CONST || a.Type == obj.TYPE_REG) && a.Index != REG_NONE && a.Scale == 0 {
-               return Ycol
+       // Change encoding generated by assemblers and remove.
+       if a == &p.From && (a.Type == obj.TYPE_CONST || a.Type == obj.TYPE_REG) && a.Index != REG_NONE && a.Scale == 0 {
+               p.From3.Type = obj.TYPE_REG
+               p.From3.Reg = a.Index
+               a.Index = 0
+       }
+
+       // To avoid changing tables, the info about p.From and p.From3 are returned together.
+       if a == &p.From && p.From3.Type != obj.TYPE_NONE {
+               if (a.Type == obj.TYPE_CONST || a.Type == obj.TYPE_REG) && p.From3.Type == obj.TYPE_REG {
+                       return Yreg2
+               }
+
+               switch p.As {
+               case obj.ATEXT, obj.ADATA, obj.AGLOBL:
+                       // we know these use From3 - ignore that
+               default:
+                       // unexpected use of From3. report invalid argument
+                       ctxt.Diag("unexpected argument: %v", obj.Dconv(p, &p.From3))
+                       return Yxxx
+               }
        }
 
        switch a.Type {
@@ -2684,17 +2708,18 @@ var ymovtab = []Movtab{
        Movtab{AMOVW, Yml, Ytask, 4, [4]uint8{0x0f, 0x00, 3, 0}},
        Movtab{AMOVW, Ytask, Yml, 3, [4]uint8{0x0f, 0x00, 1, 0}},
 
-       /* load full pointer */
+       /* load full pointer - unsupported
        Movtab{AMOVL, Yml, Ycol, 5, [4]uint8{0, 0, 0, 0}},
        Movtab{AMOVW, Yml, Ycol, 5, [4]uint8{Pe, 0, 0, 0}},
+       */
 
        /* double shift */
-       Movtab{ASHLL, Ycol, Yml, 6, [4]uint8{0xa4, 0xa5, 0, 0}},
-       Movtab{ASHRL, Ycol, Yml, 6, [4]uint8{0xac, 0xad, 0, 0}},
-       Movtab{ASHLQ, Ycol, Yml, 6, [4]uint8{Pw, 0xa4, 0xa5, 0}},
-       Movtab{ASHRQ, Ycol, Yml, 6, [4]uint8{Pw, 0xac, 0xad, 0}},
-       Movtab{ASHLW, Ycol, Yml, 6, [4]uint8{Pe, 0xa4, 0xa5, 0}},
-       Movtab{ASHRW, Ycol, Yml, 6, [4]uint8{Pe, 0xac, 0xad, 0}},
+       Movtab{ASHLL, Yreg2, Yml, 6, [4]uint8{0xa4, 0xa5, 0, 0}},
+       Movtab{ASHRL, Yreg2, Yml, 6, [4]uint8{0xac, 0xad, 0, 0}},
+       Movtab{ASHLQ, Yreg2, Yml, 6, [4]uint8{Pw, 0xa4, 0xa5, 0}},
+       Movtab{ASHRQ, Yreg2, Yml, 6, [4]uint8{Pw, 0xac, 0xad, 0}},
+       Movtab{ASHLW, Yreg2, Yml, 6, [4]uint8{Pe, 0xa4, 0xa5, 0}},
+       Movtab{ASHRW, Yreg2, Yml, 6, [4]uint8{Pe, 0xac, 0xad, 0}},
 
        /* load TLS base */
        Movtab{AMOVQ, Ytls, Yrl, 7, [4]uint8{0, 0, 0, 0}},
@@ -3490,7 +3515,7 @@ func doasm(ctxt *obj.Link, p *obj.Prog) {
                                                        ctxt.Andptr = ctxt.Andptr[1:]
                                                        ctxt.Andptr[0] = t[0]
                                                        ctxt.Andptr = ctxt.Andptr[1:]
-                                                       asmandsz(ctxt, p, &p.To, reg[int(p.From.Index)], regrex[int(p.From.Index)], 0)
+                                                       asmandsz(ctxt, p, &p.To, reg[p.From3.Reg], regrex[p.From3.Reg], 0)
                                                        ctxt.Andptr[0] = byte(p.From.Offset)
                                                        ctxt.Andptr = ctxt.Andptr[1:]
 
@@ -3499,13 +3524,12 @@ func doasm(ctxt *obj.Link, p *obj.Prog) {
                                                        default:
                                                                goto bad
 
-                                                       case REG_CL,
-                                                               REG_CX:
+                                                       case REG_CL, REG_CX:
                                                                ctxt.Andptr[0] = 0x0f
                                                                ctxt.Andptr = ctxt.Andptr[1:]
                                                                ctxt.Andptr[0] = t[1]
                                                                ctxt.Andptr = ctxt.Andptr[1:]
-                                                               asmandsz(ctxt, p, &p.To, reg[int(p.From.Index)], regrex[int(p.From.Index)], 0)
+                                                               asmandsz(ctxt, p, &p.To, reg[p.From3.Reg], regrex[p.From3.Reg], 0)
                                                        }
                                                }