cmd/internal/obj/arm64: factor out code generation for addition of 12 bit immediates

Factor out and simplify code that generates the addition of a 12 bit immediate
(the addition of a negative value is still handled via subtraction). This also
fixes the mishandling of the case where v is 0.

Change-Id: I6040f33d2fec87b772272531b3bf02390ae7f200
Reviewed-on: https://go-review.googlesource.com/c/go/+/461141
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Eric Fang <eric.fang@arm.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Joel Sing <joel@sing.id.au>
Reviewed-by: Cherry Mui <cherryyz@google.com>

diff --git a/src/cmd/internal/obj/arm64/asm7.go b/src/cmd/internal/obj/arm64/asm7.go
index 03844cba08d22c4db57fb86ac26db9323fe212a5..7dc872972888530498ca418938ad1c9731132e2a 100644 (file)
--- a/src/cmd/internal/obj/arm64/asm7.go
+++ b/src/cmd/internal/obj/arm64/asm7.go
@@ -4678,27 +4678,15 @@ func (c *ctxt7) asmout(p *obj.Prog, o *Optab, out []uint32) {
        case 74:
                //      add $O, R, Rtmp or sub $O, R, Rtmp
                //      ldp (Rtmp), (R1, R2)
-               r := int(p.From.Reg)
-               if r == obj.REG_NONE {
-                       r = int(o.param)
+               rf := p.From.Reg
+               if rf == obj.REG_NONE {
+                       rf = o.param
                }
-               if r == obj.REG_NONE {
+               if rf == obj.REG_NONE {
                        c.ctxt.Diag("invalid ldp source: %v", p)
                }
                v := int32(c.regoff(&p.From))
-
-               if v > 0 {
-                       if v > 4095 {
-                               c.ctxt.Diag("offset out of range: %v", p)
-                       }
-                       o1 = c.oaddi(p, int32(c.opirr(p, AADD)), v, r, REGTMP)
-               }
-               if v < 0 {
-                       if v < -4095 {
-                               c.ctxt.Diag("offset out of range: %v", p)
-                       }
-                       o1 = c.oaddi(p, int32(c.opirr(p, ASUB)), -v, r, REGTMP)
-               }
+               o1 = c.oaddi12(p, v, REGTMP, rf)
                o2 = c.opldpstp(p, o, 0, uint32(REGTMP), uint32(p.To.Reg), uint32(p.To.Offset), 1)
 
        case 75:
@@ -4728,26 +4716,15 @@ func (c *ctxt7) asmout(p *obj.Prog, o *Optab, out []uint32) {
                if p.From.Reg == REGTMP || p.From.Offset == REGTMP {
                        c.ctxt.Diag("cannot use REGTMP as source: %v", p)
                }
-               r := int(p.To.Reg)
-               if r == obj.REG_NONE {
-                       r = int(o.param)
+               rt := p.To.Reg
+               if rt == obj.REG_NONE {
+                       rt = o.param
                }
-               if r == obj.REG_NONE {
+               if rt == obj.REG_NONE {
                        c.ctxt.Diag("invalid stp destination: %v", p)
                }
                v := int32(c.regoff(&p.To))
-               if v > 0 {
-                       if v > 4095 {
-                               c.ctxt.Diag("offset out of range: %v", p)
-                       }
-                       o1 = c.oaddi(p, int32(c.opirr(p, AADD)), v, r, REGTMP)
-               }
-               if v < 0 {
-                       if v < -4095 {
-                               c.ctxt.Diag("offset out of range: %v", p)
-                       }
-                       o1 = c.oaddi(p, int32(c.opirr(p, ASUB)), -v, r, REGTMP)
-               }
+               o1 = c.oaddi12(p, v, REGTMP, rt)
                o2 = c.opldpstp(p, o, 0, uint32(REGTMP), uint32(p.From.Reg), uint32(p.From.Offset), 0)
 
        case 77:
@@ -7146,6 +7123,19 @@ func (c *ctxt7) oaddi(p *obj.Prog, o1 int32, v int32, r int, rt int) uint32 {
        return uint32(o1)
 }
 
+func (c *ctxt7) oaddi12(p *obj.Prog, v int32, rd, rn int16) uint32 {
+       if v < -4095 || v > 4095 {
+               c.ctxt.Diag("%v is not a 12 bit immediate: %v", v, p)
+               return 0
+       }
+       a := AADD
+       if v < 0 {
+               a = ASUB
+               v = -v
+       }
+       return c.oaddi(p, int32(c.opirr(p, a)), v, int(rn), int(rd))
+}
+
 /*
  * load a literal value into dr
  */