From: Joel Sing <joel@sing.id.au>
Date: Fri, 25 Aug 2023 18:19:40 +0000 (+1000)
Subject: cmd/internal/obj/riscv: support subtraction with a constant
X-Git-Tag: go1.22rc1~407
X-Git-Url: http://www.git.cypherpunks.ru/?p=gostls13.git;a=commitdiff_plain;h=dc74a3dd4f30c4a3df235aac8a9e84575767ba69

cmd/internal/obj/riscv: support subtraction with a constant

Allow SUB and SUBW to be specified with a constant, which are mapped
to ADDI and ADDIW with negated values.

Change-Id: I7dc55692febc81ea87393b0a3a7d23a43c30313b
Reviewed-on: https://go-review.googlesource.com/c/go/+/538915
Run-TryBot: Joel Sing <joel@sing.id.au>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: M Zhuo <mzh@golangcn.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Reviewed-by: Mark Ryan <markdryan@rivosinc.com>
Reviewed-by: Wang Yaduo <wangyaduo@linux.alibaba.com>
Reviewed-by: Mauri de Souza Meneguzzo <mauri870@gmail.com>
---

diff --git a/src/cmd/asm/internal/asm/testdata/riscv64.s b/src/cmd/asm/internal/asm/testdata/riscv64.s
index 2afa457105..072302b225 100644
--- a/src/cmd/asm/internal/asm/testdata/riscv64.s
+++ b/src/cmd/asm/internal/asm/testdata/riscv64.s
@@ -94,6 +94,10 @@ start:
 
 	SUB	X6, X5, X7				// b3836240
 	SUB	X5, X6					// 33035340
+	SUB	$-2047, X5, X6				// 1383f27f
+	SUB	$2048, X5, X6				// 13830280
+	SUB	$-2047, X5				// 9382f27f
+	SUB	$2048, X5				// 93820280
 
 	SRA	X6, X5, X7				// b3d36240
 	SRA	X5, X6					// 33535340
@@ -157,6 +161,7 @@ start:
 	ADDW	$1, X6					// 1b031300
 	SLLW	$1, X6					// 1b131300
 	SRLW	$1, X6					// 1b531300
+	SUBW	$1, X6					// 1b03f3ff
 	SRAW	$1, X6					// 1b531340
 
 	// 5.3: Load and Store Instructions (RV64I)
diff --git a/src/cmd/internal/obj/riscv/obj.go b/src/cmd/internal/obj/riscv/obj.go
index 279c8678a7..4ff1d910ce 100644
--- a/src/cmd/internal/obj/riscv/obj.go
+++ b/src/cmd/internal/obj/riscv/obj.go
@@ -69,6 +69,8 @@ func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 		switch p.As {
 		case AADD:
 			p.As = AADDI
+		case ASUB:
+			p.As, p.From.Offset = AADDI, -p.From.Offset
 		case ASLT:
 			p.As = ASLTI
 		case ASLTU:
@@ -87,6 +89,8 @@ func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 			p.As = ASRAI
 		case AADDW:
 			p.As = AADDIW
+		case ASUBW:
+			p.As, p.From.Offset = AADDIW, -p.From.Offset
 		case ASLLW:
 			p.As = ASLLIW
 		case ASRLW: