cmd/compile: revert CL/316890

This is a revert of https://go-review.googlesource.com/c/go/+/316890,
which has positive effects on debugging + DWARF variable locations
for register parameters when the reg abi is in effect, but also
turns out to interact badly with the register allocator.

Fixes #46304.

Change-Id: I624bd980493411a9cde45d44fcd3c46cad796909
Reviewed-on: https://go-review.googlesource.com/c/go/+/321830
Trust: Than McIntosh <thanm@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>

diff --git a/src/cmd/compile/internal/ssa/expand_calls.go b/src/cmd/compile/internal/ssa/expand_calls.go
index d37d06f8e7105ee7a03d65343ced1b6bee2a89c0..7e973ab20591fb8ae42eddcc542f6ca6c1c67451 100644 (file)
--- a/src/cmd/compile/internal/ssa/expand_calls.go
+++ b/src/cmd/compile/internal/ssa/expand_calls.go
@@ -1717,22 +1717,6 @@ func (x *expandState) newArgToMemOrRegs(baseArg, toReplace *Value, offset int64,
        } else {
                w = baseArg.Block.NewValue0IA(pos, op, t, auxInt, aux)
        }
-       // If we are creating an OpArgIntReg/OpArgFloatReg that
-       // corresponds to an in-param that fits entirely in a register,
-       // then enter it into the name/value table. The LocalSlot
-       // is somewhat fictitious, since there is no incoming live
-       // memory version of the parameter, but we need an entry in
-       // NamedValues in order for ssa debug tracking to include
-       // the value in the tracking analysis.
-       if len(pa.Registers) == 1 {
-               loc := LocalSlot{N: aux.Name, Type: t, Off: 0}
-               values, ok := x.f.NamedValues[loc]
-               if !ok {
-                       ploc := x.f.localSlotAddr(loc)
-                       x.f.Names = append(x.f.Names, ploc)
-               }
-               x.f.NamedValues[loc] = append(values, w)
-       }
        x.commonArgs[key] = w
        if toReplace != nil {
                toReplace.copyOf(w)

diff --git a/test/fixedbugs/issue46304.go b/test/fixedbugs/issue46304.go
new file mode 100644 (file)
index 0000000..b8ecfc9
--- /dev/null
+++ b/test/fixedbugs/issue46304.go
@@ -0,0 +1,76 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This testcase caused a crash when the register ABI was in effect,
+// on amd64 (problem with register allocation).
+
+package main
+
+type Op struct {
+       tag   string
+       _x    []string
+       _q    [20]uint64
+       plist []P
+}
+
+type P struct {
+       tag string
+       _x  [10]uint64
+       b   bool
+}
+
+type M int
+
+//go:noinline
+func (w *M) walkP(p *P) *P {
+       np := &P{}
+       *np = *p
+       np.tag += "new"
+       return np
+}
+
+func (w *M) walkOp(op *Op) *Op {
+       if op == nil {
+               return nil
+       }
+
+       orig := op
+       cloned := false
+       clone := func() {
+               if !cloned {
+                       cloned = true
+                       op = &Op{}
+                       *op = *orig
+               }
+       }
+
+       pCloned := false
+       for i := range op.plist {
+               if s := w.walkP(&op.plist[i]); s != &op.plist[i] {
+                       if !pCloned {
+                               pCloned = true
+                               clone()
+                               op.plist = make([]P, len(orig.plist))
+                               copy(op.plist, orig.plist)
+                       }
+                       op.plist[i] = *s
+               }
+       }
+
+       return op
+}
+
+func main() {
+       var ww M
+       w := &ww
+       p1 := P{tag: "a"}
+       p1._x[1] = 9
+       o := Op{tag: "old", plist: []P{p1}}
+       no := w.walkOp(&o)
+       if no.plist[0].tag != "anew" {
+               panic("bad")
+       }
+}