cmd/internal/obj/riscv: add support of PCALIGN directive
Add support for PCALIGN directive on riscv.
This directive can be used within Go asm to align instruction
by padding NOP directives.
This patch also adds a test to verify the correctness of the PCALIGN
directive.
Original credit by Cooper Qu (Alibaba)
https://gitee.com/xuantie_riscv/xuantie-patch
Change-Id: I8b6524a2bf81a1baf7c9d04b7da2db6c1a7b428f
Reviewed-on: https://go-review.googlesource.com/c/go/+/541740
Run-TryBot: M Zhuo <mzh@golangcn.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Wang Yaduo <wangyaduo@linux.alibaba.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Mark Ryan <markdryan@rivosinc.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
diff --git a/src/cmd/internal/obj/riscv/asm_test.go b/src/cmd/internal/obj/riscv/asm_test.go
index afe0525..96ea230 100644
--- a/src/cmd/internal/obj/riscv/asm_test.go
+++ b/src/cmd/internal/obj/riscv/asm_test.go
@@ -9,8 +9,10 @@
"fmt"
"internal/testenv"
"os"
+ "os/exec"
"path/filepath"
"runtime"
+ "strings"
"testing"
)
@@ -277,3 +279,33 @@
t.Errorf("Branch test failed: %v\n%s", err, out)
}
}
+
+func TestPCAlign(t *testing.T) {
+ dir := t.TempDir()
+ tmpfile := filepath.Join(dir, "x.s")
+ asm := `
+TEXT _stub(SB),$0-0
+ FENCE
+ PCALIGN $8
+ FENCE
+ RET
+`
+ if err := os.WriteFile(tmpfile, []byte(asm), 0644); err != nil {
+ t.Fatal(err)
+ }
+ cmd := exec.Command(testenv.GoToolPath(t), "tool", "asm", "-o", filepath.Join(dir, "x.o"), "-S", tmpfile)
+ cmd.Env = append(os.Environ(), "GOARCH=riscv64", "GOOS=linux")
+ out, err := cmd.CombinedOutput()
+ if err != nil {
+ t.Errorf("Failed to assemble: %v\n%s", err, out)
+ }
+ // The expected instruction sequence after alignment:
+ // FENCE
+ // NOP
+ // FENCE
+ // RET
+ want := "0f 00 f0 0f 13 00 00 00 0f 00 f0 0f 67 80 00 00"
+ if !strings.Contains(string(out), want) {
+ t.Errorf("PCALIGN test failed - got %s\nwant %s", out, want)
+ }
+}
diff --git a/src/cmd/internal/obj/riscv/obj.go b/src/cmd/internal/obj/riscv/obj.go
index 93bda45..11d6c20 100644
--- a/src/cmd/internal/obj/riscv/obj.go
+++ b/src/cmd/internal/obj/riscv/obj.go
@@ -308,6 +308,12 @@
for _, ins := range instructionsForProg(p) {
pc += int64(ins.length())
}
+
+ if p.As == obj.APCALIGN {
+ alignedValue := p.From.Offset
+ v := pcAlignPadLength(pc, alignedValue)
+ pc += int64(v)
+ }
}
return pc
}
@@ -733,6 +739,16 @@
p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: high, Sym: cursym}
p.Link.To.Offset = low
}
+
+ case obj.APCALIGN:
+ alignedValue := p.From.Offset
+ if (alignedValue&(alignedValue-1) != 0) || 4 > alignedValue || alignedValue > 2048 {
+ ctxt.Diag("alignment value of an instruction must be a power of two and in the range [4, 2048], got %d\n", alignedValue)
+ }
+ // Update the current text symbol alignment value.
+ if int32(alignedValue) > cursym.Func().Align {
+ cursym.Func().Align = int32(alignedValue)
+ }
}
}
@@ -744,6 +760,10 @@
}
}
+func pcAlignPadLength(pc int64, alignedValue int64) int {
+ return int(-pc & (alignedValue - 1))
+}
+
func stacksplit(ctxt *obj.Link, p *obj.Prog, cursym *obj.LSym, newprog obj.ProgAlloc, framesize int64) *obj.Prog {
// Leaf function with no frame is effectively NOSPLIT.
if framesize == 0 {
@@ -1708,6 +1728,7 @@
obj.ANOP: pseudoOpEncoding,
obj.ADUFFZERO: pseudoOpEncoding,
obj.ADUFFCOPY: pseudoOpEncoding,
+ obj.APCALIGN: pseudoOpEncoding,
}
// encodingForAs returns the encoding for an obj.As.
@@ -2425,6 +2446,17 @@
rel.Sym = addr.Sym
rel.Add = addr.Offset
rel.Type = rt
+
+ case obj.APCALIGN:
+ alignedValue := p.From.Offset
+ v := pcAlignPadLength(p.Pc, alignedValue)
+ offset := p.Pc
+ for ; v >= 4; v -= 4 {
+ // NOP
+ cursym.WriteBytes(ctxt, offset, []byte{0x13, 0, 0, 0})
+ offset += 4
+ }
+ continue
}
offset := p.Pc
