cmd/internal/obj/loong64: clean up code for short conditional branches

Untangle the logic so the preparation of operands and actual assembling
(branch range checking included) are properly separated, making future
changes easier to review and maintain. No functional change intended.

Change-Id: I1f73282f9d92ff23d84846453d3597ba66d207d1
Reviewed-on: https://go-review.googlesource.com/c/go/+/478376
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

diff --git a/src/cmd/internal/obj/loong64/asm.go b/src/cmd/internal/obj/loong64/asm.go
index 4e1c36e11b8102045e0f089b7c8826ace2b2dd6d..77ffbfb4c345ca692117e57c8c7c327542a7e0ed 100644 (file)
--- a/src/cmd/internal/obj/loong64/asm.go
+++ b/src/cmd/internal/obj/loong64/asm.go
@@ -1179,26 +1179,26 @@ func (c *ctxt0) asmout(p *obj.Prog, o *Optab, out []uint32) {
 
        case 6: // beq r1,[r2],sbra
                v := int32(0)
-               vcmp := int32(0)
                if p.To.Target() != nil {
                        v = int32(p.To.Target().Pc-p.Pc) >> 2
                }
-               if v < 0 {
-                       vcmp = -v
-               }
-               if (p.As == ABFPT || p.As == ABFPF) && ((uint32(vcmp))>>21)&0x7FF != 0 {
-                       c.ctxt.Diag("21 bit-width, short branch too far\n%v", p)
-               } else if p.As != ABFPT && p.As != ABFPF && (v<<16)>>16 != v {
-                       c.ctxt.Diag("16 bit-width, short branch too far\n%v", p)
-               }
+               rd, rj := p.Reg, p.From.Reg
                if p.As == ABGTZ || p.As == ABLEZ {
-                       o1 = OP_16IRR(c.opirr(p.As), uint32(v), uint32(p.Reg), uint32(p.From.Reg))
-               } else if p.As == ABFPT || p.As == ABFPF {
-                       // BCNEZ cj offset21 ,cj = fcc0
-                       // BCEQZ cj offset21 ,cj = fcc0
+                       rd, rj = rj, rd
+               }
+               switch p.As {
+               case ABFPT, ABFPF:
+                       if (v<<11)>>11 != v {
+                               c.ctxt.Diag("21 bit-width, short branch too far\n%v", p)
+                       }
+                       // FCC0 is the implicit source operand, now that we
+                       // don't register-allocate from the FCC bank.
                        o1 = OP_16IR_5I(c.opirr(p.As), uint32(v), uint32(REG_FCC0))
-               } else {
-                       o1 = OP_16IRR(c.opirr(p.As), uint32(v), uint32(p.From.Reg), uint32(p.Reg))
+               default:
+                       if (v<<16)>>16 != v {
+                               c.ctxt.Diag("16 bit-width, short branch too far\n%v", p)
+                       }
+                       o1 = OP_16IRR(c.opirr(p.As), uint32(v), uint32(rj), uint32(rd))
                }
 
        case 7: // mov r, soreg