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cmd/compile/internal/ssa: note zero-width Ops

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Add a bool to opInfo to indicate if an Op never results in any
instructions. This is a conservative approximation: some operations,
like Copy, may or may not generate code depending on their arguments.

I built the list by reading each arch's ssaGenValue function. Hopefully
I got them all.

Change-Id: I130b251b65f18208294e129bb7ddc3f91d57d31d
Reviewed-on: https://go-review.googlesource.com/97957
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Heschi Kreinick 2018-02-28 16:30:07 -05:00
parent b77aad0891
commit caa1b4afbd
12 changed files with 107 additions and 74 deletions
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34
src/cmd/compile/internal/ssa/gen/genericOps.go
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@ -285,8 +285,8 @@ var genericOps = []opData{
// Data movement, max argument length for Phi is indefinite so just pick
// a really large number
{name: "Phi", argLength: -1}, // select an argument based on which predecessor block we came from
{name: "Copy", argLength: 1}, // output = arg0
{name: "Phi", argLength: -1, zeroWidth: true}, // select an argument based on which predecessor block we came from
{name: "Copy", argLength: 1}, // output = arg0
// Convert converts between pointers and integers.
// We have a special op for this so as to not confuse GC
// (particularly stack maps). It takes a memory arg so it
@ -311,8 +311,8 @@ var genericOps = []opData{
{name: "ConstSlice"}, // nil slice
// Constant-like things
{name: "InitMem"}, // memory input to the function.
{name: "Arg", aux: "SymOff", symEffect: "Read"}, // argument to the function. aux=GCNode of arg, off = offset in that arg.
{name: "InitMem", zeroWidth: true}, // memory input to the function.
{name: "Arg", aux: "SymOff", symEffect: "Read", zeroWidth: true}, // argument to the function. aux=GCNode of arg, off = offset in that arg.
// The address of a variable. arg0 is the base pointer.
// If the variable is a global, the base pointer will be SB and
@ -321,9 +321,9 @@ var genericOps = []opData{
// the Aux field will be a *gc.Node.
{name: "Addr", argLength: 1, aux: "Sym", symEffect: "Addr"}, // Address of a variable. Arg0=SP or SB. Aux identifies the variable.
{name: "SP"}, // stack pointer
{name: "SB", typ: "Uintptr"}, // static base pointer (a.k.a. globals pointer)
{name: "Invalid"}, // unused value
{name: "SP", zeroWidth: true}, // stack pointer
{name: "SB", typ: "Uintptr", zeroWidth: true}, // static base pointer (a.k.a. globals pointer)
{name: "Invalid"}, // unused value
// Memory operations
{name: "Load", argLength: 2}, // Load from arg0. arg1=memory
@ -395,10 +395,10 @@ var genericOps = []opData{
{name: "NilCheck", argLength: 2, typ: "Void"}, // arg0=ptr, arg1=mem. Panics if arg0 is nil. Returns void.
// Pseudo-ops
{name: "GetG", argLength: 1}, // runtime.getg() (read g pointer). arg0=mem
{name: "GetClosurePtr"}, // get closure pointer from dedicated register
{name: "GetCallerPC"}, // for getcallerpc intrinsic
{name: "GetCallerSP"}, // for getcallersp intrinsic
{name: "GetG", argLength: 1, zeroWidth: true}, // runtime.getg() (read g pointer). arg0=mem
{name: "GetClosurePtr"}, // get closure pointer from dedicated register
{name: "GetCallerPC"}, // for getcallerpc intrinsic
{name: "GetCallerSP"}, // for getcallersp intrinsic
// Indexing operations
{name: "PtrIndex", argLength: 2}, // arg0=ptr, arg1=index. Computes ptr+sizeof(*v.type)*index, where index is extended to ptrwidth type
@ -451,10 +451,10 @@ var genericOps = []opData{
// Unknown value. Used for Values whose values don't matter because they are dead code.
{name: "Unknown"},
{name: "VarDef", argLength: 1, aux: "Sym", typ: "Mem", symEffect: "None"}, // aux is a *gc.Node of a variable that is about to be initialized. arg0=mem, returns mem
{name: "VarKill", argLength: 1, aux: "Sym", symEffect: "None"}, // aux is a *gc.Node of a variable that is known to be dead. arg0=mem, returns mem
{name: "VarLive", argLength: 1, aux: "Sym", symEffect: "Read"}, // aux is a *gc.Node of a variable that must be kept live. arg0=mem, returns mem
{name: "KeepAlive", argLength: 2, typ: "Mem"}, // arg[0] is a value that must be kept alive until this mark. arg[1]=mem, returns mem
{name: "VarDef", argLength: 1, aux: "Sym", typ: "Mem", symEffect: "None", zeroWidth: true}, // aux is a *gc.Node of a variable that is about to be initialized. arg0=mem, returns mem
{name: "VarKill", argLength: 1, aux: "Sym", symEffect: "None"}, // aux is a *gc.Node of a variable that is known to be dead. arg0=mem, returns mem
{name: "VarLive", argLength: 1, aux: "Sym", symEffect: "Read", zeroWidth: true}, // aux is a *gc.Node of a variable that must be kept live. arg0=mem, returns mem
{name: "KeepAlive", argLength: 2, typ: "Mem", zeroWidth: true}, // arg[0] is a value that must be kept alive until this mark. arg[1]=mem, returns mem
// Ops for breaking 64-bit operations on 32-bit architectures
{name: "Int64Make", argLength: 2, typ: "UInt64"}, // arg0=hi, arg1=lo
@ -481,8 +481,8 @@ var genericOps = []opData{
{name: "Cvt64Fto64U", argLength: 1}, // float64 -> uint64, only used on archs that has the instruction
// pseudo-ops for breaking Tuple
{name: "Select0", argLength: 1}, // the first component of a tuple
{name: "Select1", argLength: 1}, // the second component of a tuple
{name: "Select0", argLength: 1, zeroWidth: true}, // the first component of a tuple
{name: "Select1", argLength: 1, zeroWidth: true}, // the second component of a tuple
// Atomic operations used for semantically inlining runtime/internal/atomic.
// Atomic loads return a new memory so that the loads are properly ordered