cmd/internal/obj/riscv: store relocation details in obj.Prog.RestArgs

Store the relocation offset and symbol in obj.Prog.RestArgs, rather than overloading obj.Prog.From and having to deal with invalid offsets potentially existing when the instruction is encoded. Change-Id: Iff0d678361677e78b41b887f6eba08cee94fccb3 Reviewed-on: https://go-review.googlesource.com/c/go/+/218197 Reviewed-by: Cherry Zhang <[email protected]> Run-TryBot: Cherry Zhang <[email protected]> TryBot-Result: Gobot Gobot <[email protected]>
kamermans · Mar 15, 2020 · 2b920cb · 2b920cb
1 parent dad94e7
commit 2b920cb
Showing 1 changed file with 16 additions and 30 deletions.
diff --git a/src/cmd/internal/obj/riscv/obj.go b/src/cmd/internal/obj/riscv/obj.go
@@ -46,13 +46,12 @@ func jalrToSym(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc, lr int16) *ob
 
 	to := p.To
 
-	// This offset isn't really encoded with either instruction. It will be
-	// extracted for a relocation later.
 	p.As = AAUIPC
-	p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: to.Offset, Sym: to.Sym}
+	p.Mark |= NEED_PCREL_ITYPE_RELOC
+	p.RestArgs = []obj.Addr{obj.Addr{Type: obj.TYPE_CONST, Offset: to.Offset, Sym: to.Sym}}
+	p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: 0}
 	p.Reg = 0
 	p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_TMP}
-	p.Mark |= NEED_PCREL_ITYPE_RELOC
 	p = obj.Appendp(p, newprog)
 
 	// Leave Sym only for the CALL reloc in assemble.
@@ -324,13 +323,12 @@ func rewriteMOV(ctxt *obj.Link, newprog obj.ProgAlloc, p *obj.Prog) {
 			as := p.As
 			to := p.To
 
-			// The offset is not really encoded with either instruction.
-			// It will be extracted later for a relocation.
 			p.As = AAUIPC
-			p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: p.From.Offset, Sym: p.From.Sym}
+			p.Mark |= NEED_PCREL_ITYPE_RELOC
+			p.RestArgs = []obj.Addr{obj.Addr{Type: obj.TYPE_CONST, Offset: p.From.Offset, Sym: p.From.Sym}}
+			p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: 0}
 			p.Reg = 0
 			p.To = obj.Addr{Type: obj.TYPE_REG, Reg: to.Reg}
-			p.Mark |= NEED_PCREL_ITYPE_RELOC
 			p = obj.Appendp(p, newprog)
 
 			p.As = movToLoad(as)
@@ -385,13 +383,12 @@ func rewriteMOV(ctxt *obj.Link, newprog obj.ProgAlloc, p *obj.Prog) {
 				as := p.As
 				from := p.From
 
-				// The offset is not really encoded with either instruction.
-				// It will be extracted later for a relocation.
 				p.As = AAUIPC
-				p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: p.To.Offset, Sym: p.To.Sym}
+				p.Mark |= NEED_PCREL_STYPE_RELOC
+				p.RestArgs = []obj.Addr{obj.Addr{Type: obj.TYPE_CONST, Offset: p.To.Offset, Sym: p.To.Sym}}
+				p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: 0}
 				p.Reg = 0
 				p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_TMP}
-				p.Mark |= NEED_PCREL_STYPE_RELOC
 				p = obj.Appendp(p, newprog)
 
 				p.As = movToStore(as)
@@ -452,13 +449,12 @@ func rewriteMOV(ctxt *obj.Link, newprog obj.ProgAlloc, p *obj.Prog) {
 			// ADDI $off_lo, R
 			to := p.To
 
-			// The offset is not really encoded with either instruction.
-			// It will be extracted later for a relocation.
 			p.As = AAUIPC
-			p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: p.From.Offset, Sym: p.From.Sym}
+			p.Mark |= NEED_PCREL_ITYPE_RELOC
+			p.RestArgs = []obj.Addr{obj.Addr{Type: obj.TYPE_CONST, Offset: p.From.Offset, Sym: p.From.Sym}}
+			p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: 0}
 			p.Reg = 0
 			p.To = to
-			p.Mark |= NEED_PCREL_ITYPE_RELOC
 			p = obj.Appendp(p, newprog)
 
 			p.As = AADDI
@@ -1413,13 +1409,6 @@ func validateB(p *obj.Prog) {
 }
 
 func validateU(p *obj.Prog) {
-	if p.As == AAUIPC && p.Mark&(NEED_PCREL_ITYPE_RELOC|NEED_PCREL_STYPE_RELOC) != 0 {
-		// TODO(sorear): Hack.  The Offset is being used here to temporarily
-		// store the relocation addend, not as an actual offset to assemble,
-		// so it's OK for it to be out of range.  Is there a more valid way
-		// to represent this state?
-		return
-	}
 	wantImmI(p, "from", p.From, 20)
 	wantIntRegAddr(p, "to", &p.To)
 }
@@ -1868,20 +1857,17 @@ func assemble(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 				ctxt.Diag("AUIPC needing PC-relative reloc missing following instruction")
 				break
 			}
-			if p.From.Sym == nil {
+			addr := p.RestArgs[0]
+			if addr.Sym == nil {
 				ctxt.Diag("AUIPC needing PC-relative reloc missing symbol")
 				break
 			}
 
-			// The relocation offset can be larger than the maximum
-			// size of an AUIPC, so zero p.From.Offset to avoid any
-			// attempt to assemble it.
 			rel := obj.Addrel(cursym)
 			rel.Off = int32(p.Pc)
 			rel.Siz = 8
-			rel.Sym = p.From.Sym
-			rel.Add = p.From.Offset
-			p.From.Offset = 0
+			rel.Sym = addr.Sym
+			rel.Add = addr.Offset
 			rel.Type = rt
 		}