cmd/compile: fix WriteFuncMap for new ABI.

replaced old type-based logic with new abi-based logic;
earlier versions of this CL compared them for equality.
For not-in-a-register, they match everywhere tested.

also modified GetFrameOffset to make it more like the one it replaces;
the LocalsOffset is subtracted.

Change-Id: I65ce7f0646c493c277df6b6f46e4839a0d886ac9
Reviewed-on: https://go-review.googlesource.com/c/go/+/302072
Trust: David Chase <drchase@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/compile/internal/abi/abiutils.go

@@ -236,16 +236,22 @@ func (a *ABIParamAssignment) SpillOffset() int32 {
 	return a.offset
 }
 
-// FrameOffset returns the location that a value would spill to, if any exists.
+// FrameOffset returns the frame-pointer-relative location that a function
-// For register-allocated inputs, that is their spill offset reserved for morestack
+// would spill its input or output parameter to, if such a spill slot exists.
-// (might as well use it, it is there); for stack-allocated inputs and outputs,
+// For register-allocated inputs that is their spill offset reserved for morestack;
-// that is their location on the stack.  For register-allocated outputs, there is
+// for stack-allocated inputs and outputs, that is their location on the stack.
-// no defined spill area, so return -1.
+// For register-allocated outputs, there is no defined spill area, so return -1.
+// (In a future version of the ABI, register-resident inputs may lose their defined
+// spill area to help reduce stack sizes.)
 func (a *ABIParamAssignment) FrameOffset(i *ABIParamResultInfo) int64 {
-	if len(a.Registers) == 0 || a.offset == -1 {
+	if a.offset == -1 {
-		return int64(a.offset)
+		return -1
 	}
-	return int64(a.offset) + i.SpillAreaOffset()
+	if len(a.Registers) == 0 { // passed on stack
+		return int64(a.offset) - i.config.LocalsOffset()
+	}
+	// spill area for registers
+	return int64(a.offset) + i.SpillAreaOffset() - i.config.LocalsOffset()
 }
 
 // RegAmounts holds a specified number of integer/float registers.
@@ -462,7 +468,7 @@ func (config *ABIConfig) updateOffset(result *ABIParamResultInfo, f *types.Field
 		// Getting this wrong breaks stackmaps, see liveness/plive.go:WriteFuncMap and typebits/typebits.go:Set
 		parameterUpdateMu.Lock()
 		defer parameterUpdateMu.Unlock()
-		off := a.FrameOffset(result) - config.LocalsOffset()
+		off := a.FrameOffset(result)
 		fOffset := f.Offset
 		if fOffset == types.BOGUS_FUNARG_OFFSET {
 			// Set the Offset the first time. After that, we may recompute it, but it should never change.

src/cmd/compile/internal/gc/compile.go

@@ -45,8 +45,8 @@ func enqueueFunc(fn *ir.Func) {
 		ssagen.InitLSym(fn, false)
 		types.CalcSize(fn.Type()) // TODO register args; remove this once all is done by abiutils
 		a := ssagen.AbiForFunc(fn)
-		a.ABIAnalyze(fn.Type(), true) // will set parameter spill/home locations correctly
+		abiInfo := a.ABIAnalyze(fn.Type(), true) // will set parameter spill/home locations correctly
-		liveness.WriteFuncMap(fn)
+		liveness.WriteFuncMap(fn, abiInfo)
 		return
 	}
 

src/cmd/compile/internal/liveness/plive.go

@@ -22,6 +22,7 @@ import (
 	"sort"
 	"strings"
 
+	"cmd/compile/internal/abi"
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/bitvec"
 	"cmd/compile/internal/ir"
@@ -1449,32 +1450,36 @@ func isfat(t *types.Type) bool {
 	return false
 }
 
-// TODO THIS IS ALL WRONG AND NEEDS TO USE ABI.
+// WriteFuncMap writes the pointer bitmaps for bodyless function fn's
-func WriteFuncMap(fn *ir.Func) {
+// inputs and outputs as the value of symbol <fn>.args_stackmap.
+// If fn has outputs, two bitmaps are written, otherwise just one.
+func WriteFuncMap(fn *ir.Func, abiInfo *abi.ABIParamResultInfo) {
 	if ir.FuncName(fn) == "_" || fn.Sym().Linkname != "" {
 		return
 	}
 	types.CalcSize(fn.Type())
-	lsym := base.Ctxt.Lookup(fn.LSym.Name + ".args_stackmap")
+	nptr := int(abiInfo.ArgWidth() / int64(types.PtrSize))
-	nptr := int(fn.Type().ArgWidth() / int64(types.PtrSize))
 	bv := bitvec.New(int32(nptr) * 2)
+
+	for _, p := range abiInfo.InParams() {
+		typebits.Set(p.Type, p.FrameOffset(abiInfo), bv)
+	}
+
 	nbitmap := 1
 	if fn.Type().NumResults() > 0 {
 		nbitmap = 2
 	}
+	lsym := base.Ctxt.Lookup(fn.LSym.Name + ".args_stackmap")
 	off := objw.Uint32(lsym, 0, uint32(nbitmap))
 	off = objw.Uint32(lsym, off, uint32(bv.N))
-
-	if ir.IsMethod(fn) {
-		typebits.Set(fn.Type().Recvs(), 0, bv)
-	}
-	if fn.Type().NumParams() > 0 {
-		typebits.Set(fn.Type().Params(), 0, bv)
-	}
 	off = objw.BitVec(lsym, off, bv)
 
 	if fn.Type().NumResults() > 0 {
-		typebits.Set(fn.Type().Results(), 0, bv)
+		for _, p := range abiInfo.OutParams() {
+			if len(p.Registers) == 0 {
+				typebits.Set(p.Type, p.FrameOffset(abiInfo), bv)
+			}
+		}
 		off = objw.BitVec(lsym, off, bv)
 	}
 

src/cmd/compile/internal/objw/objw.go

@@ -11,6 +11,8 @@ import (
 	"cmd/internal/obj"
 )
 
+// Uint8 writes an unsigned byte v into s at offset off,
+// and returns the next unused offset (i.e., off+1).
 func Uint8(s *obj.LSym, off int, v uint8) int {
 	return UintN(s, off, uint64(v), 1)
 }
@@ -27,6 +29,8 @@ func Uintptr(s *obj.LSym, off int, v uint64) int {
 	return UintN(s, off, v, types.PtrSize)
 }
 
+// UintN writes an unsigned integer v of size wid bytes into s at offset off,
+// and returns the next unused offset.
 func UintN(s *obj.LSym, off int, v uint64, wid int) int {
 	if off&(wid-1) != 0 {
 		base.Fatalf("duintxxLSym: misaligned: v=%d wid=%d off=%d", v, wid, off)
@@ -62,6 +66,8 @@ func Global(s *obj.LSym, width int32, flags int16) {
 	base.Ctxt.Globl(s, int64(width), int(flags))
 }
 
+// Bitvec writes the contents of bv into s as sequence of bytes
+// in little-endian order, and returns the next unused offset.
 func BitVec(s *obj.LSym, off int, bv bitvec.BitVec) int {
 	// Runtime reads the bitmaps as byte arrays. Oblige.
 	for j := 0; int32(j) < bv.N; j += 8 {

src/cmd/compile/internal/ssagen/ssa.go

@@ -367,7 +367,7 @@ func (s *state) emitOpenDeferInfo() {
 			f := getParam(r.n, j)
 			off = dvarint(x, off, -okOffset(arg.FrameOffset()))
 			off = dvarint(x, off, f.Type.Size())
-			off = dvarint(x, off, okOffset(pri.InParam(j+argAdjust).FrameOffset(pri))-ab.LocalsOffset()) // defer does not want the fixed frame adjustment
+			off = dvarint(x, off, okOffset(pri.InParam(j+argAdjust).FrameOffset(pri)))
 		}
 	}
 }