cmd/internal/obj/riscv: handle FEQ/FNEG/SEQZ/SNEZ

Based on riscv-go port.

Updates #27532

Change-Id: I5e7f45955e1dfdb9d09cc6a4e6f3ce81216d411d
Reviewed-on: https://go-review.googlesource.com/c/go/+/204628Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/asm/internal/asm/testdata/riscvenc.s

@@ -282,3 +282,25 @@ start:
 	// real address and updates the immediates for both instructions.
 	CALL	asmtest(SB)				// 970f0000
 	JMP	asmtest(SB)				// 970f0000
+
+	SEQZ	X15, X15				// 93b71700
+	SNEZ	X15, X15				// b337f000
+
+	// F extension
+	FNEGS	F0, F1					// d3100020
+
+	// TODO(jsing): FNES gets encoded as FEQS+XORI - this should
+	// be handled as a single *obj.Prog so that the full two
+	// instruction encoding is tested here.
+	FNES	F0, F1, X7				// d3a300a0
+
+	// D extension
+	FNEGD	F0, F1					// d3100022
+	FEQD	F0, F1, X5				// d3a200a2
+	FLTD	F0, F1, X5				// d39200a2
+	FLED	F0, F1, X5				// d38200a2
+
+	// TODO(jsing): FNED gets encoded as FEQD+XORI - this should
+	// be handled as a single *obj.Prog so that the full two
+	// instruction encoding is tested here.
+	FNED	F0, F1, X5				// d3a200a2

src/cmd/internal/obj/riscv/obj.go

@@ -221,6 +221,27 @@ func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 	case AFCVTWS, AFCVTLS, AFCVTWUS, AFCVTLUS, AFCVTWD, AFCVTLD, AFCVTWUD, AFCVTLUD:
 		// Set the rounding mode in funct3 to round to zero.
 		p.Scond = 1
+
+	case ASEQZ:
+		// SEQZ rs, rd -> SLTIU $1, rs, rd
+		p.As = ASLTIU
+		p.Reg = p.From.Reg
+		p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: 1}
+
+	case ASNEZ:
+		// SNEZ rs, rd -> SLTU rs, x0, rd
+		p.As = ASLTU
+		p.Reg = REG_ZERO
+
+	case AFNEGS:
+		// FNEGS rs, rd -> FSGNJNS rs, rs, rd
+		p.As = AFSGNJNS
+		p.Reg = p.From.Reg
+
+	case AFNEGD:
+		// FNEGD rs, rd -> FSGNJND rs, rs, rd
+		p.As = AFSGNJND
+		p.Reg = p.From.Reg
 	}
 }
 
@@ -595,6 +616,37 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 					jalrToSym(ctxt, p, newprog, REG_ZERO)
 				}
 			}
+
+		// Replace FNE[SD] with FEQ[SD] and NOT.
+		case AFNES:
+			if p.To.Type != obj.TYPE_REG {
+				ctxt.Diag("progedit: FNES needs an integer register output")
+			}
+			dst := p.To.Reg
+			p.As = AFEQS
+			p = obj.Appendp(p, newprog)
+
+			p.As = AXORI // [bit] xor 1 = not [bit]
+			p.From.Type = obj.TYPE_CONST
+			p.From.Offset = 1
+			p.Reg = dst
+			p.To.Type = obj.TYPE_REG
+			p.To.Reg = dst
+
+		case AFNED:
+			if p.To.Type != obj.TYPE_REG {
+				ctxt.Diag("progedit: FNED needs an integer register output")
+			}
+			dst := p.To.Reg
+			p.As = AFEQD
+			p = obj.Appendp(p, newprog)
+
+			p.As = AXORI // [bit] xor 1 = not [bit]
+			p.From.Type = obj.TYPE_CONST
+			p.From.Offset = 1
+			p.Reg = dst
+			p.To.Type = obj.TYPE_REG
+			p.To.Reg = dst
 		}
 	}