cmd/internal/obj/riscv: simplify instructionsForMOV

Rather than handling shift based scaling in two locations, rework logic
so there is a single exit path.

Change-Id: I832b4932d53183736050059a11019ced08281b3b
Reviewed-on: https://go-review.googlesource.com/c/go/+/523455
Reviewed-by: M Zhuo <mzh@golangcn.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Joel Sing <joel@sing.id.au>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Mark Ryan <markdryan@rivosinc.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

1 files changed, 8 insertions, 13 deletions

diff --git a/src/cmd/internal/obj/riscv/obj.go b/src/cmd/internal/obj/riscv/obj.go
index 776c3a8df6..36812833a9 100644
--- a/src/cmd/internal/obj/riscv/obj.go
+++ b/src/cmd/internal/obj/riscv/obj.go
@@ -1992,20 +1992,15 @@ func instructionsForMOV(p *obj.Prog) []*instruction {
 		ins.as, ins.rs1, ins.rs2, ins.imm = AADDI, REG_ZERO, obj.REG_NONE, low
 
 		// LUI is only necessary if the constant does not fit in 12 bits.
-		if high == 0 {
-			if insSLLI != nil {
-				inss = append(inss, insSLLI)
+		if high != 0 {
+			// LUI top20bits(c), R
+			// ADD bottom12bits(c), R, R
+			insLUI := &instruction{as: ALUI, rd: ins.rd, imm: high}
+			inss = []*instruction{insLUI}
+			if low != 0 {
+				ins.as, ins.rs1 = AADDIW, ins.rd
+				inss = append(inss, ins)
 			}
-			break
-		}
-
-		// LUI top20bits(c), R
-		// ADD bottom12bits(c), R, R
-		insLUI := &instruction{as: ALUI, rd: ins.rd, imm: high}
-		inss = []*instruction{insLUI}
-		if low != 0 {
-			ins.as, ins.rs1 = AADDIW, ins.rd
-			inss = append(inss, ins)
 		}
 		if insSLLI != nil {
 			inss = append(inss, insSLLI)