[dev.typeparams] all: merge dev.regabi (77365c5) into dev.typeparams

Conflicts:

- src/cmd/compile/internal/gc/main.go
- test/fixedbugs/issue15055.go

Merge List:

+ 2021-01-05 77365c5ed7 [dev.regabi] cmd/compile: add Name.Canonical and move Byval
+ 2021-01-05 e09783cbc0 [dev.regabi] cmd/compile: make ir.StaticValue safer
+ 2021-01-05 9aa950c407 [dev.regabi] cmd/compile: make ir.OuterValue safer
+ 2021-01-05 eb626409d1 [dev.regabi] cmd/compile: simplify CaptureVars
+ 2021-01-05 c28ca67a96 [dev.regabi] cmd/compile: fix ir.Dump for []*CaseClause, etc
+ 2021-01-04 f24e40c14a [dev.regabi] cmd/compile: remove Name.Class_ accessors
+ 2021-01-04 d89705e087 [dev.regabi] cmd/compile: fix re-export of parameters
+ 2021-01-04 290b4154b7 [dev.regabi] cmd/compile: fix ICE due to large uint64 constants
+ 2021-01-04 a30fd52884 [dev.regabi] cmd/compile: use ir.NewNameAt in SubstArgTypes
+ 2021-01-03 8fc44cf0fa [dev.regabi] cmd/compile: remove a couple CloneName calls
+ 2021-01-03 907a4bfdc7 [dev.regabi] cmd/compile: fix map assignment order
+ 2021-01-03 f2e6dab048 [dev.regabi] cmd/compile: remove walkReturn "common case" path
+ 2021-01-03 d36a6bf44d [dev.regabi] cmd/compile: improve walkReturn common case
+ 2021-01-03 a317067d65 [dev.regabi] cmd/compile: improve ascompatee
+ 2021-01-03 5d80a590a2 [dev.regabi] cmd/compile: simplify walkReturn
+ 2021-01-03 bb1b6c95c2 [dev.regabi] cmd/compile: remove Node.{,Set}Walkdef
+ 2021-01-03 57c426c9a5 [dev.regabi] cmd/compile: tighten typecheckdef to *ir.Name
+ 2021-01-03 b1747756e3 [dev.regabi] cmd/compile: reorganize escape analysis somewhat
+ 2021-01-02 f2538033c0 [dev.regabi] cmd/compile: remove Nodes.Set [generated]
+ 2021-01-02 2f2d4b4e68 [dev.regabi] cmd/compile: remove {Ptr,Set}Init from Node interface
+ 2021-01-01 1544a03198 [dev.regabi] cmd/compile: refactor redundant type conversion [generated]
+ 2021-01-01 7958a23ea3 [dev.regabi] cmd/compile: use *ir.Name where possible in inl.go
+ 2021-01-01 bfa97ba48f [dev.regabi] test: add another closure test case
+ 2021-01-01 67ad695416 [dev.regabi] cmd/compile: split escape analysis state
+ 2021-01-01 fad9a8b528 [dev.regabi] cmd/compile: simplify inlining of closures
+ 2021-01-01 7d55669847 [dev.regabi] cmd/compile: simplify dwarfgen.declPos
+ 2021-01-01 9ed1577779 [dev.regabi] cmd/compile: remove Func.ClosureEnter
+ 2021-01-01 ece345aa69 [dev.regabi] cmd/compile: expand documentation for Func.Closure{Vars,Enter}
+ 2021-01-01 6ddbc75efd [dev.regabi] cmd/compile: earlier deadcode removal
+ 2021-01-01 68e6fa4f68 [dev.regabi] cmd/compile: fix package-initialization order
+ 2021-01-01 3a4474cdfd [dev.regabi] cmd/compile: some more manual shuffling
+ 2021-01-01 0f1d2129c4 [dev.regabi] cmd/compile: reshuffle type-checking code [generated]
+ 2021-01-01 b8fd3440cd [dev.regabi] cmd/compile: report unused variables during typecheck
+ 2021-01-01 fd22df9905 [dev.regabi] cmd/compile: remove idempotent Name() calls [generated]
+ 2020-12-31 dfbcff80c6 [dev.regabi] cmd/compile: make copyExpr return *ir.Name directly
+ 2020-12-31 77fd81a3e6 [dev.regabi] cmd/compile: use names for keep alive variables in function call
+ 2020-12-31 8fe1197654 [dev.regabi] cmd/compile: remove Name.orig
+ 2020-12-31 477b049060 [dev.regabi] cmd/compile: fix printing of method expressions
+ 2020-12-30 178c667db2 [dev.regabi] cmd/compile: fix OSLICEARR comments
+ 2020-12-30 f0d99def5b [dev.regabi] cmd/compile: add newline to ir.Dump
+ 2020-12-30 451693af71 [dev.regabi] cmd/compile: simplify typecheckdef
+ 2020-12-30 0c1a899a6c [dev.regabi] cmd/compile: fix defined-pointer method call check
+ 2020-12-30 f9b67f76a5 [dev.regabi] cmd/compile: change ir.DoChildren to use bool result type
+ 2020-12-30 499851bac8 [dev.regabi] cmd/compile: generalize ir/mknode.go
+ 2020-12-30 82ab3d1448 [dev.regabi] cmd/compile: use *ir.Name for Decl.X
+ 2020-12-30 9958b7ed3e [dev.regabi] cmd/compile: unexport ir.FmtNode
+ 2020-12-29 f5816624cd [dev.regabi] cmd/compile: change AddrExpr.Alloc to AddrExpr.Prealloc
+ 2020-12-29 850aa7c60c [dev.regabi] cmd/compile: use *ir.Name instead of ir.Node for CaseClause.Var
+ 2020-12-29 37babc97bb [dev.regabi] cmd/compile: allow visitor visits *ir.Name
+ 2020-12-29 5cf3c87fa6 [dev.regabi] cmd/compile: generate case/comm clause functions in mknode.go
+ 2020-12-29 b3e1ec97fd [dev.regabi] cmd/compile: move new addrtaken bit back to the old name
+ 2020-12-29 0620c674dd [dev.regabi] cmd/compile: remove original addrtaken bit
+ 2020-12-29 0523d525ae [dev.regabi] cmd/compile: separate out address taken computation from typechecker
+ 2020-12-29 9ea272e5ec [dev.regabi] cmd/compile: simplify ir.Func somewhat
+ 2020-12-29 e40cb4d4ae [dev.regabi] cmd/compile: remove more unused code
+ 2020-12-29 6f30c95048 [dev.regabi] cmd/compile: remove unneeded indirection
+ 2020-12-29 171fc6f223 [dev.regabi] cmd/compile: remove workarounds for go/constant issues
+ 2020-12-29 33801cdc62 [dev.regabi] cmd/compile: use Ntype where possible
+ 2020-12-29 82ad3083f8 [dev.regabi] cmd/compile: remove typ from AssignOpStmt
+ 2020-12-29 e34c44a7c4 [dev.regabi] cmd/compile: refactoring typecheck arith
+ 2020-12-29 a5ec920160 [dev.regabi] cmd/compile: more Linksym cleanup
+ 2020-12-29 ec59b197d5 [dev.regabi] cmd/compile: rewrite to use linksym helpers [generated]
+ 2020-12-29 25c613c02d [dev.regabi] cmd/compile: add Linksym helpers
+ 2020-12-29 289da2b33e [dev.regabi] cmd/compile: move Node.Opt to Name
+ 2020-12-29 6acbae4fcc [dev.regabi] cmd/compile: address some ir TODOs
+ 2020-12-29 4629f6a51d [dev.regabi] cmd/compile: merge {Selector,CallPart,Method}Expr
+ 2020-12-29 e563715b30 [dev.regabi] cmd/compile: remove Sym.Importdef
+ 2020-12-29 3f370b75fb [dev.regabi] cmd/compile: cleanup //go:generate directives

Change-Id: Ibb254630924ac5873ebda6762ceb066f54a82649

1 files changed, 152 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/deadcode/deadcode.go b/src/cmd/compile/internal/deadcode/deadcode.go
new file mode 100644
index 0000000000..c409320fc4
--- /dev/null
+++ b/src/cmd/compile/internal/deadcode/deadcode.go
@@ -0,0 +1,152 @@
+// Copyright 2009 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.
+
+package deadcode
+
+import (
+	"go/constant"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+)
+
+func Func(fn *ir.Func) {
+	stmts(&fn.Body)
+
+	if len(fn.Body) == 0 {
+		return
+	}
+
+	for _, n := range fn.Body {
+		if len(n.Init()) > 0 {
+			return
+		}
+		switch n.Op() {
+		case ir.OIF:
+			n := n.(*ir.IfStmt)
+			if !ir.IsConst(n.Cond, constant.Bool) || len(n.Body) > 0 || len(n.Else) > 0 {
+				return
+			}
+		case ir.OFOR:
+			n := n.(*ir.ForStmt)
+			if !ir.IsConst(n.Cond, constant.Bool) || ir.BoolVal(n.Cond) {
+				return
+			}
+		default:
+			return
+		}
+	}
+
+	fn.Body = []ir.Node{ir.NewBlockStmt(base.Pos, nil)}
+}
+
+func stmts(nn *ir.Nodes) {
+	var lastLabel = -1
+	for i, n := range *nn {
+		if n != nil && n.Op() == ir.OLABEL {
+			lastLabel = i
+		}
+	}
+	for i, n := range *nn {
+		// Cut is set to true when all nodes after i'th position
+		// should be removed.
+		// In other words, it marks whole slice "tail" as dead.
+		cut := false
+		if n == nil {
+			continue
+		}
+		if n.Op() == ir.OIF {
+			n := n.(*ir.IfStmt)
+			n.Cond = expr(n.Cond)
+			if ir.IsConst(n.Cond, constant.Bool) {
+				var body ir.Nodes
+				if ir.BoolVal(n.Cond) {
+					n.Else = ir.Nodes{}
+					body = n.Body
+				} else {
+					n.Body = ir.Nodes{}
+					body = n.Else
+				}
+				// If "then" or "else" branch ends with panic or return statement,
+				// it is safe to remove all statements after this node.
+				// isterminating is not used to avoid goto-related complications.
+				// We must be careful not to deadcode-remove labels, as they
+				// might be the target of a goto. See issue 28616.
+				if body := body; len(body) != 0 {
+					switch body[(len(body) - 1)].Op() {
+					case ir.ORETURN, ir.ORETJMP, ir.OPANIC:
+						if i > lastLabel {
+							cut = true
+						}
+					}
+				}
+			}
+		}
+
+		if len(n.Init()) != 0 {
+			stmts(n.(ir.InitNode).PtrInit())
+		}
+		switch n.Op() {
+		case ir.OBLOCK:
+			n := n.(*ir.BlockStmt)
+			stmts(&n.List)
+		case ir.OFOR:
+			n := n.(*ir.ForStmt)
+			stmts(&n.Body)
+		case ir.OIF:
+			n := n.(*ir.IfStmt)
+			stmts(&n.Body)
+			stmts(&n.Else)
+		case ir.ORANGE:
+			n := n.(*ir.RangeStmt)
+			stmts(&n.Body)
+		case ir.OSELECT:
+			n := n.(*ir.SelectStmt)
+			for _, cas := range n.Cases {
+				stmts(&cas.Body)
+			}
+		case ir.OSWITCH:
+			n := n.(*ir.SwitchStmt)
+			for _, cas := range n.Cases {
+				stmts(&cas.Body)
+			}
+		}
+
+		if cut {
+			*nn = (*nn)[:i+1]
+			break
+		}
+	}
+}
+
+func expr(n ir.Node) ir.Node {
+	// Perform dead-code elimination on short-circuited boolean
+	// expressions involving constants with the intent of
+	// producing a constant 'if' condition.
+	switch n.Op() {
+	case ir.OANDAND:
+		n := n.(*ir.LogicalExpr)
+		n.X = expr(n.X)
+		n.Y = expr(n.Y)
+		if ir.IsConst(n.X, constant.Bool) {
+			if ir.BoolVal(n.X) {
+				return n.Y // true && x => x
+			} else {
+				return n.X // false && x => false
+			}
+		}
+	case ir.OOROR:
+		n := n.(*ir.LogicalExpr)
+		n.X = expr(n.X)
+		n.Y = expr(n.Y)
+		if ir.IsConst(n.X, constant.Bool) {
+			if ir.BoolVal(n.X) {
+				return n.X // true || x => true
+			} else {
+				return n.Y // false || x => x
+			}
+		}
+	}
+	return n
+}