From 37d4532867b9c49f936cb8e394dec44d8985fe29 Mon Sep 17 00:00:00 2001
From: Ben Shi <powerman1st@163.com>
Date: Thu, 2 Sep 2021 00:06:42 +0000
Subject: [PATCH] cmd/internal/obj/riscv: simplify addition with constant
This CL simplifies riscv addition (add r, imm) to
(ADDI (ADDI r, imm/2), imm-imm/2) if imm is in specific ranges.
(-4096 <= imm <= -2049 or 2048 <= imm <= 4094)
There is little impact to the go1 benchmark, while the total
size of pkg/linux_riscv64 decreased by about 11KB.
Change-Id: I236eb8af3b83bb35ce9c0b318fc1d235e8ab9a4e
GitHub-Last-Rev: a2f56a07635344a40d6b8a9571f236743122be34
GitHub-Pull-Request: golang/go#48110
Reviewed-on: https://go-review.googlesource.com/c/go/+/346689
Run-TryBot: Ben Shi <powerman1st@163.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Joel Sing <joel@sing.id.au>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Trust: Michael Munday <mike.munday@lowrisc.org>
---
src/cmd/internal/obj/riscv/obj.go | 21 +++++++++++++++++++++
test/codegen/arithmetic.go | 8 ++++++++
2 files changed, 29 insertions(+)
diff --git a/src/cmd/internal/obj/riscv/obj.go b/src/cmd/internal/obj/riscv/obj.go
index 73f62c007dd..6de967319c4 100644
--- a/src/cmd/internal/obj/riscv/obj.go
+++ b/src/cmd/internal/obj/riscv/obj.go
@@ -774,6 +774,27 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
break // no need to split
}
+ // Split into two additions if possible.
+ imm := q.From.Offset
+ const minInt12, maxInt12 = -(1 << 11), (1 << 11) - 1
+ if q.As == AADDI && 2*minInt12 <= imm && imm <= 2*maxInt12 {
+ imm0, imm1 := imm/2, imm-imm/2
+ // ADDI $(imm/2), REG, TO
+ p.Spadj = 0 // needed if TO is SP
+ p.As = AADDI
+ p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: imm0}
+ p.Reg = q.Reg
+ p.To = q.To
+ p = obj.Appendp(p, newprog)
+ // ADDI $(imm-imm/2), TO, TO
+ p.Spadj = q.Spadj
+ p.As = AADDI
+ p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: imm1}
+ p.Reg = q.To.Reg
+ p.To = q.To
+ break
+ }
+
p.As = ALUI
p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: high}
p.Reg = 0
diff --git a/test/codegen/arithmetic.go b/test/codegen/arithmetic.go
index eb95416b6aa..754c5c9bc97 100644
--- a/test/codegen/arithmetic.go
+++ b/test/codegen/arithmetic.go
@@ -575,3 +575,11 @@ func constantFold3(i, j int) int {
r := (5 * i) * (6 * j)
return r
}
+
+func addConst(i int64) (int64, int64) {
+ // riscv64:`ADDI`,-`LUI`
+ a := i + 3001
+ // riscv64:`LUI`,`ADDIW`
+ b := i + 5009
+ return a, b
+}
--
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