From 7ce2a8383d154ca1860286a9b5c8a1e6cf151a90 Mon Sep 17 00:00:00 2001 From: Matthew Dempsky Date: Sat, 16 Jan 2021 19:35:39 -0800 Subject: [PATCH] [dev.regabi] cmd/compile: simplify stack temp initialization This CL simplifies the previous one a little bit further, by combining reordering stack-temporary initialization and getting rid of an unneeded temporary variable. (Does not pass toolstash -cmp.) Change-Id: I17799dfe368484f33a8ddd0ab4f68647d6262147 Reviewed-on: https://go-review.googlesource.com/c/go/+/284225 Trust: Matthew Dempsky Run-TryBot: Matthew Dempsky TryBot-Result: Go Bot Reviewed-by: Cuong Manh Le --- src/cmd/compile/internal/walk/complit.go | 17 +++++++---------- src/cmd/compile/internal/walk/temp.go | 19 ++++++------------- 2 files changed, 13 insertions(+), 23 deletions(-) diff --git a/src/cmd/compile/internal/walk/complit.go b/src/cmd/compile/internal/walk/complit.go index a7db453550..97e820238b 100644 --- a/src/cmd/compile/internal/walk/complit.go +++ b/src/cmd/compile/internal/walk/complit.go @@ -344,21 +344,18 @@ func slicelit(ctxt initContext, n *ir.CompLitExpr, var_ ir.Node, init *ir.Nodes) if !types.Identical(t, x.Type()) { panic("dotdotdot base type does not match order's assigned type") } - a = initStackTemp(init, x, vstat != nil) + a = initStackTemp(init, x, vstat) } else if n.Esc() == ir.EscNone { - if vstat == nil { - // TODO(mdempsky): Remove this useless temporary. - // It's only needed to keep toolstash happy. - typecheck.Temp(t) - } - a = initStackTemp(init, typecheck.Temp(t), vstat != nil) + a = initStackTemp(init, typecheck.Temp(t), vstat) } else { a = ir.NewUnaryExpr(base.Pos, ir.ONEW, ir.TypeNode(t)) } appendWalkStmt(init, ir.NewAssignStmt(base.Pos, vauto, a)) - if vstat != nil { - // copy static to heap (4) + if vstat != nil && n.Prealloc == nil && n.Esc() != ir.EscNone { + // If we allocated on the heap with ONEW, copy the static to the + // heap (4). We skip this for stack temporaries, because + // initStackTemp already handled the copy. a = ir.NewStarExpr(base.Pos, vauto) appendWalkStmt(init, ir.NewAssignStmt(base.Pos, a, vstat)) } @@ -535,7 +532,7 @@ func anylit(n ir.Node, var_ ir.Node, init *ir.Nodes) { var r ir.Node if n.Prealloc != nil { // n.Prealloc is stack temporary used as backing store. - r = initStackTemp(init, n.Prealloc, false) + r = initStackTemp(init, n.Prealloc, nil) } else { r = ir.NewUnaryExpr(base.Pos, ir.ONEW, ir.TypeNode(n.X.Type())) r.SetEsc(n.Esc()) diff --git a/src/cmd/compile/internal/walk/temp.go b/src/cmd/compile/internal/walk/temp.go index 901cb770f3..9879a6c69d 100644 --- a/src/cmd/compile/internal/walk/temp.go +++ b/src/cmd/compile/internal/walk/temp.go @@ -12,19 +12,12 @@ import ( ) // initStackTemp appends statements to init to initialize the given -// temporary variable, and then returns the expression &tmp. If vardef -// is true, then the variable is initialized with OVARDEF, and the -// caller must ensure the variable is later assigned before use; -// otherwise, it's zero initialized. -// -// TODO(mdempsky): Change callers to provide tmp's initial value, -// rather than just vardef, to make this safer/easier to use. -func initStackTemp(init *ir.Nodes, tmp *ir.Name, vardef bool) *ir.AddrExpr { - if vardef { - init.Append(ir.NewUnaryExpr(base.Pos, ir.OVARDEF, tmp)) - } else { - appendWalkStmt(init, ir.NewAssignStmt(base.Pos, tmp, nil)) +// temporary variable to val, and then returns the expression &tmp. +func initStackTemp(init *ir.Nodes, tmp *ir.Name, val ir.Node) *ir.AddrExpr { + if val != nil && !types.Identical(tmp.Type(), val.Type()) { + base.Fatalf("bad initial value for %L: %L", tmp, val) } + appendWalkStmt(init, ir.NewAssignStmt(base.Pos, tmp, val)) return typecheck.Expr(typecheck.NodAddr(tmp)).(*ir.AddrExpr) } @@ -32,7 +25,7 @@ func initStackTemp(init *ir.Nodes, tmp *ir.Name, vardef bool) *ir.AddrExpr { // allocated temporary variable of the given type. Statements to // zero-initialize tmp are appended to init. func stackTempAddr(init *ir.Nodes, typ *types.Type) *ir.AddrExpr { - return initStackTemp(init, typecheck.Temp(typ), false) + return initStackTemp(init, typecheck.Temp(typ), nil) } // stackBufAddr returns thte expression &tmp, where tmp is a newly