cmd/internal/obj/riscv: implement prologue and epilogue
Based on riscv-go port.
Updates #27532
Change-Id: If552225552bf8d27c29b08de31146dd34986a3a1
Reviewed-on: https://go-review.googlesource.com/c/go/+/204630
Run-TryBot: Joel Sing <joel@sing.id.au>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
diff --git a/src/cmd/internal/obj/riscv/obj.go b/src/cmd/internal/obj/riscv/obj.go
index f2ff4ff..53cd860 100644
--- a/src/cmd/internal/obj/riscv/obj.go
+++ b/src/cmd/internal/obj/riscv/obj.go
@@ -504,6 +504,24 @@
}
}
+// containsCall reports whether the symbol contains a CALL (or equivalent)
+// instruction. Must be called after progedit.
+func containsCall(sym *obj.LSym) bool {
+ // CALLs are CALL or JAL(R) with link register LR.
+ for p := sym.Func.Text; p != nil; p = p.Link {
+ switch p.As {
+ case obj.ACALL:
+ return true
+ case AJAL, AJALR:
+ if p.To.Type == obj.TYPE_REG && p.To.Reg == REG_LR {
+ return true
+ }
+ }
+ }
+
+ return false
+}
+
// setPCs sets the Pc field in all instructions reachable from p.
// It uses pc as the initial value.
func setPCs(p *obj.Prog, pc int64) {
@@ -551,11 +569,20 @@
}
}
+// preprocess generates prologue and epilogue code, computes PC-relative branch
+// and jump offsets, and resolves pseudo-registers.
+//
+// preprocess is called once per linker symbol.
+//
+// When preprocess finishes, all instructions in the symbol are either
+// concrete, real RISC-V instructions or directive pseudo-ops like TEXT,
+// PCDATA, and FUNCDATA.
func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
if cursym.Func.Text == nil || cursym.Func.Text.Link == nil {
return
}
+ // Generate the prologue.
text := cursym.Func.Text
if text.As != obj.ATEXT {
ctxt.Diag("preprocess: found symbol that does not start with TEXT directive")
@@ -577,10 +604,126 @@
}
}
+ if !containsCall(cursym) {
+ text.From.Sym.Set(obj.AttrLeaf, true)
+ if stacksize == 0 {
+ // A leaf function with no locals has no frame.
+ text.From.Sym.Set(obj.AttrNoFrame, true)
+ }
+ }
+
+ // Save LR unless there is no frame.
+ if !text.From.Sym.NoFrame() {
+ stacksize += ctxt.FixedFrameSize()
+ }
+
cursym.Func.Args = text.To.Val.(int32)
cursym.Func.Locals = int32(stacksize)
- // TODO(jsing): Implement.
+ prologue := text
+
+ if !cursym.Func.Text.From.Sym.NoSplit() {
+ prologue = stacksplit(ctxt, prologue, cursym, newprog, stacksize) // emit split check
+ }
+
+ if stacksize != 0 {
+ prologue = ctxt.StartUnsafePoint(prologue, newprog)
+
+ // Actually save LR.
+ prologue = obj.Appendp(prologue, newprog)
+ prologue.As = AMOV
+ prologue.From = obj.Addr{Type: obj.TYPE_REG, Reg: REG_LR}
+ prologue.To = obj.Addr{Type: obj.TYPE_MEM, Reg: REG_SP, Offset: -stacksize}
+
+ // Insert stack adjustment.
+ prologue = obj.Appendp(prologue, newprog)
+ prologue.As = AADDI
+ prologue.From = obj.Addr{Type: obj.TYPE_CONST, Offset: -stacksize}
+ prologue.Reg = REG_SP
+ prologue.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_SP}
+ prologue.Spadj = int32(stacksize)
+
+ prologue = ctxt.EndUnsafePoint(prologue, newprog, -1)
+ }
+
+ if cursym.Func.Text.From.Sym.Wrapper() {
+ // if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
+ //
+ // MOV g_panic(g), X11
+ // BNE X11, ZERO, adjust
+ // end:
+ // NOP
+ // ...rest of function..
+ // adjust:
+ // MOV panic_argp(X11), X12
+ // ADD $(autosize+FIXED_FRAME), SP, X13
+ // BNE X12, X13, end
+ // ADD $FIXED_FRAME, SP, X12
+ // MOV X12, panic_argp(X11)
+ // JMP end
+ //
+ // The NOP is needed to give the jumps somewhere to land.
+
+ ldpanic := obj.Appendp(prologue, newprog)
+
+ ldpanic.As = AMOV
+ ldpanic.From = obj.Addr{Type: obj.TYPE_MEM, Reg: REGG, Offset: 4 * int64(ctxt.Arch.PtrSize)} // G.panic
+ ldpanic.Reg = 0
+ ldpanic.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_X11}
+
+ bneadj := obj.Appendp(ldpanic, newprog)
+ bneadj.As = ABNE
+ bneadj.From = obj.Addr{Type: obj.TYPE_REG, Reg: REG_X11}
+ bneadj.Reg = REG_ZERO
+ bneadj.To.Type = obj.TYPE_BRANCH
+
+ endadj := obj.Appendp(bneadj, newprog)
+ endadj.As = obj.ANOP
+
+ last := endadj
+ for last.Link != nil {
+ last = last.Link
+ }
+
+ getargp := obj.Appendp(last, newprog)
+ getargp.As = AMOV
+ getargp.From = obj.Addr{Type: obj.TYPE_MEM, Reg: REG_X11, Offset: 0} // Panic.argp
+ getargp.Reg = 0
+ getargp.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_X12}
+
+ bneadj.Pcond = getargp
+
+ calcargp := obj.Appendp(getargp, newprog)
+ calcargp.As = AADDI
+ calcargp.From = obj.Addr{Type: obj.TYPE_CONST, Offset: stacksize + ctxt.FixedFrameSize()}
+ calcargp.Reg = REG_SP
+ calcargp.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_X13}
+
+ testargp := obj.Appendp(calcargp, newprog)
+ testargp.As = ABNE
+ testargp.From = obj.Addr{Type: obj.TYPE_REG, Reg: REG_X12}
+ testargp.Reg = REG_X13
+ testargp.To.Type = obj.TYPE_BRANCH
+ testargp.Pcond = endadj
+
+ adjargp := obj.Appendp(testargp, newprog)
+ adjargp.As = AADDI
+ adjargp.From = obj.Addr{Type: obj.TYPE_CONST, Offset: int64(ctxt.Arch.PtrSize)}
+ adjargp.Reg = REG_SP
+ adjargp.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_X12}
+
+ setargp := obj.Appendp(adjargp, newprog)
+ setargp.As = AMOV
+ setargp.From = obj.Addr{Type: obj.TYPE_REG, Reg: REG_X12}
+ setargp.Reg = 0
+ setargp.To = obj.Addr{Type: obj.TYPE_MEM, Reg: REG_X11, Offset: 0} // Panic.argp
+
+ godone := obj.Appendp(setargp, newprog)
+ godone.As = AJAL
+ godone.From = obj.Addr{Type: obj.TYPE_REG, Reg: REG_ZERO}
+ godone.To.Type = obj.TYPE_BRANCH
+ godone.Pcond = endadj
+ }
// Update stack-based offsets.
for p := cursym.Func.Text; p != nil; p = p.Link {
@@ -588,8 +731,7 @@
stackOffset(&p.To, stacksize)
}
- // Additional instruction rewriting. Any rewrites that change the number
- // of instructions must occur here (before jump target resolution).
+ // Additional instruction rewriting.
for p := cursym.Func.Text; p != nil; p = p.Link {
switch p.As {
case obj.AGETCALLERPC:
@@ -621,6 +763,46 @@
}
}
+ case obj.ARET:
+ // Replace RET with epilogue.
+ retJMP := p.To.Sym
+
+ if stacksize != 0 {
+ // Restore LR.
+ p.As = AMOV
+ p.From = obj.Addr{Type: obj.TYPE_MEM, Reg: REG_SP, Offset: 0}
+ p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_LR}
+ p = obj.Appendp(p, newprog)
+
+ p.As = AADDI
+ p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: stacksize}
+ p.Reg = REG_SP
+ p.To = obj.Addr{Type: obj.TYPE_REG, Reg: REG_SP}
+ p.Spadj = int32(-stacksize)
+ p = obj.Appendp(p, newprog)
+ }
+
+ if retJMP != nil {
+ p.As = obj.ARET
+ p.To.Sym = retJMP
+ p = jalrToSym(ctxt, p, newprog, REG_ZERO)
+ } else {
+ p.As = AJALR
+ p.From.Type = obj.TYPE_CONST
+ p.From.Offset = 0
+ p.Reg = REG_LR
+ p.To.Type = obj.TYPE_REG
+ p.To.Reg = REG_ZERO
+ }
+
+ // "Add back" the stack removed in the previous instruction.
+ //
+ // This is to avoid confusing pctospadj, which sums
+ // Spadj from function entry to each PC, and shouldn't
+ // count adjustments from earlier epilogues, since they
+ // won't affect later PCs.
+ p.Spadj = int32(stacksize)
+
// Replace FNE[SD] with FEQ[SD] and NOT.
case AFNES:
if p.To.Type != obj.TYPE_REG {
@@ -864,6 +1046,152 @@
}
}
+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 {
+ return p
+ }
+
+ // MOV g_stackguard(g), X10
+ p = obj.Appendp(p, newprog)
+ p.As = AMOV
+ p.From.Type = obj.TYPE_MEM
+ p.From.Reg = REGG
+ p.From.Offset = 2 * int64(ctxt.Arch.PtrSize) // G.stackguard0
+ if cursym.CFunc() {
+ p.From.Offset = 3 * int64(ctxt.Arch.PtrSize) // G.stackguard1
+ }
+ p.To.Type = obj.TYPE_REG
+ p.To.Reg = REG_X10
+
+ var to_done, to_more *obj.Prog
+
+ if framesize <= objabi.StackSmall {
+ // small stack: SP < stackguard
+ // BLTU SP, stackguard, done
+ p = obj.Appendp(p, newprog)
+ p.As = ABLTU
+ p.From.Type = obj.TYPE_REG
+ p.From.Reg = REG_X10
+ p.Reg = REG_SP
+ p.To.Type = obj.TYPE_BRANCH
+ to_done = p
+ } else if framesize <= objabi.StackBig {
+ // large stack: SP-framesize < stackguard-StackSmall
+ // ADD $-(framesize-StackSmall), SP, X11
+ // BLTU X11, stackguard, done
+ p = obj.Appendp(p, newprog)
+ // TODO(sorear): logic inconsistent with comment, but both match all non-x86 arches
+ p.As = AADDI
+ p.From.Type = obj.TYPE_CONST
+ p.From.Offset = -(int64(framesize) - objabi.StackSmall)
+ p.Reg = REG_SP
+ p.To.Type = obj.TYPE_REG
+ p.To.Reg = REG_X11
+
+ p = obj.Appendp(p, newprog)
+ p.As = ABLTU
+ p.From.Type = obj.TYPE_REG
+ p.From.Reg = REG_X10
+ p.Reg = REG_X11
+ p.To.Type = obj.TYPE_BRANCH
+ to_done = p
+ } else {
+ // Such a large stack we need to protect against wraparound.
+ // If SP is close to zero:
+ // SP-stackguard+StackGuard <= framesize + (StackGuard-StackSmall)
+ // The +StackGuard on both sides is required to keep the left side positive:
+ // SP is allowed to be slightly below stackguard. See stack.h.
+ //
+ // Preemption sets stackguard to StackPreempt, a very large value.
+ // That breaks the math above, so we have to check for that explicitly.
+ // // stackguard is X10
+ // MOV $StackPreempt, X11
+ // BEQ X10, X11, more
+ // ADD $StackGuard, SP, X11
+ // SUB X10, X11
+ // MOV $(framesize+(StackGuard-StackSmall)), X10
+ // BGTU X11, X10, done
+ p = obj.Appendp(p, newprog)
+ p.As = AMOV
+ p.From.Type = obj.TYPE_CONST
+ p.From.Offset = objabi.StackPreempt
+ p.To.Type = obj.TYPE_REG
+ p.To.Reg = REG_X11
+
+ p = obj.Appendp(p, newprog)
+ to_more = p
+ p.As = ABEQ
+ p.From.Type = obj.TYPE_REG
+ p.From.Reg = REG_X10
+ p.Reg = REG_X11
+ p.To.Type = obj.TYPE_BRANCH
+
+ p = obj.Appendp(p, newprog)
+ p.As = AADDI
+ p.From.Type = obj.TYPE_CONST
+ p.From.Offset = int64(objabi.StackGuard)
+ p.Reg = REG_SP
+ p.To.Type = obj.TYPE_REG
+ p.To.Reg = REG_X11
+
+ p = obj.Appendp(p, newprog)
+ p.As = ASUB
+ p.From.Type = obj.TYPE_REG
+ p.From.Reg = REG_X10
+ p.Reg = REG_X11
+ p.To.Type = obj.TYPE_REG
+ p.To.Reg = REG_X11
+
+ p = obj.Appendp(p, newprog)
+ p.As = AMOV
+ p.From.Type = obj.TYPE_CONST
+ p.From.Offset = int64(framesize) + int64(objabi.StackGuard) - objabi.StackSmall
+ p.To.Type = obj.TYPE_REG
+ p.To.Reg = REG_X10
+
+ p = obj.Appendp(p, newprog)
+ p.As = ABLTU
+ p.From.Type = obj.TYPE_REG
+ p.From.Reg = REG_X10
+ p.Reg = REG_X11
+ p.To.Type = obj.TYPE_BRANCH
+ to_done = p
+ }
+
+ p = ctxt.EmitEntryLiveness(cursym, p, newprog)
+
+ // CALL runtime.morestack(SB)
+ p = obj.Appendp(p, newprog)
+ p.As = obj.ACALL
+ p.To.Type = obj.TYPE_BRANCH
+ if cursym.CFunc() {
+ p.To.Sym = ctxt.Lookup("runtime.morestackc")
+ } else if !cursym.Func.Text.From.Sym.NeedCtxt() {
+ p.To.Sym = ctxt.Lookup("runtime.morestack_noctxt")
+ } else {
+ p.To.Sym = ctxt.Lookup("runtime.morestack")
+ }
+ if to_more != nil {
+ to_more.Pcond = p
+ }
+ p = jalrToSym(ctxt, p, newprog, REG_X5)
+
+ // JMP start
+ p = obj.Appendp(p, newprog)
+ p.As = AJAL
+ p.To = obj.Addr{Type: obj.TYPE_BRANCH}
+ p.From = obj.Addr{Type: obj.TYPE_REG, Reg: REG_ZERO}
+ p.Pcond = cursym.Func.Text.Link
+
+ // placeholder for to_done's jump target
+ p = obj.Appendp(p, newprog)
+ p.As = obj.ANOP // zero-width place holder
+ to_done.Pcond = p
+
+ return p
+}
+
// signExtend sign extends val starting at bit bit.
func signExtend(val int64, bit uint) int64 {
return val << (64 - bit) >> (64 - bit)
