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cmd/internal/obj/riscv: split immediates larger than 12-bits
Handle immediates larger than 12-bits by rewriting as an LUI instruction with the high bits, followed by the original instruction with the low bits. Based on the riscv-go port. Updates #27532 Change-Id: I8ed6d6e6db06fb8a27f3ab75f467ec2b7ff1f075 Reviewed-on: https://go-review.googlesource.com/c/go/+/204626 Reviewed-by: Cherry Zhang <cherryyz@google.com> Run-TryBot: Cherry Zhang <cherryyz@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org>
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@ -486,6 +486,116 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
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}
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}
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// Split immediates larger than 12-bits.
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for p := cursym.Func.Text; p != nil; p = p.Link {
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switch p.As {
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// <opi> $imm, REG, TO
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case AADDI, AANDI, AORI, AXORI:
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// LUI $high, TMP
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// ADDI $low, TMP, TMP
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// <op> TMP, REG, TO
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q := *p
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low, high, err := Split32BitImmediate(p.From.Offset)
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if err != nil {
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ctxt.Diag("%v: constant %d too large", p, p.From.Offset, err)
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}
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if high == 0 {
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break // no need to split
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}
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p.As = ALUI
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p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: high}
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p.Reg = 0
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p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_TMP}
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p.Spadj = 0 // needed if TO is SP
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p = obj.Appendp(p, newprog)
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p.As = AADDIW
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p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: low}
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p.Reg = REG_TMP
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p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_TMP}
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p = obj.Appendp(p, newprog)
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switch q.As {
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case AADDI:
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p.As = AADD
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case AANDI:
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p.As = AAND
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case AORI:
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p.As = AOR
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case AXORI:
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p.As = AXOR
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default:
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ctxt.Diag("progedit: unsupported inst %v for splitting", q)
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}
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p.Spadj = q.Spadj
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p.To = q.To
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p.Reg = q.Reg
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p.From = obj.Addr{Type: obj.TYPE_REG, Reg: REG_TMP}
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// <load> $imm, REG, TO (load $imm+(REG), TO)
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// <store> $imm, REG, TO (store $imm+(TO), REG)
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case ALD, ALB, ALH, ALW, ALBU, ALHU, ALWU,
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ASD, ASB, ASH, ASW:
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// LUI $high, TMP
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// ADDI $low, TMP, TMP
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q := *p
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low, high, err := Split32BitImmediate(p.From.Offset)
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if err != nil {
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ctxt.Diag("%v: constant %d too large", p, p.From.Offset)
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}
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if high == 0 {
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break // no need to split
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}
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switch q.As {
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case ALD, ALB, ALH, ALW, ALBU, ALHU, ALWU:
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// LUI $high, TMP
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// ADD TMP, REG, TMP
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// <load> $low, TMP, TO
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p.As = ALUI
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p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: high}
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p.Reg = 0
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p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_TMP}
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p.Spadj = 0 // needed if TO is SP
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p = obj.Appendp(p, newprog)
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p.As = AADD
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p.From = obj.Addr{Type: obj.TYPE_REG, Reg: REG_TMP}
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p.Reg = q.Reg
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p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_TMP}
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p = obj.Appendp(p, newprog)
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p.As = q.As
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p.To = q.To
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p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: low}
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p.Reg = REG_TMP
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case ASD, ASB, ASH, ASW:
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// LUI $high, TMP
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// ADD TMP, TO, TMP
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// <store> $low, REG, TMP
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p.As = ALUI
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p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: high}
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p.Reg = 0
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p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_TMP}
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p.Spadj = 0 // needed if TO is SP
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p = obj.Appendp(p, newprog)
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p.As = AADD
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p.From = obj.Addr{Type: obj.TYPE_REG, Reg: REG_TMP}
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p.Reg = q.To.Reg
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p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_TMP}
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p = obj.Appendp(p, newprog)
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p.As = q.As
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p.Reg = q.Reg
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p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_TMP}
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p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: low}
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}
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}
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}
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setPCs(cursym.Func.Text, 0)
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// Resolve branch and jump targets.
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