all: explode GOEXPERIMENT=regabi into 5 sub-experiments

This separates GOEXPERIMENT=regabi into five sub-experiments:
regabiwrappers, regabig, regabireflect, regabidefer, and regabiargs.
Setting GOEXPERIMENT=regabi now implies the working subset of these
(currently, regabiwrappers, regabig, and regabireflect).

This simplifies testing, helps derisk the register ABI project,
and will also help with performance comparisons.

This replaces the -abiwrap flag to the compiler and linker with
the regabiwrappers experiment.

As part of this, regabiargs now enables registers for all calls
in the compiler. Previously, this was statically disabled in
regabiEnabledForAllCompilation, but now that we can control it
independently, this isn't necessary.

For #40724.

Change-Id: I5171e60cda6789031f2ef034cc2e7c5d62459122
Reviewed-on: https://go-review.googlesource.com/c/go/+/302070
Trust: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: David Chase <drchase@google.com>

8 files changed, 18 insertions, 23 deletions

diff --git a/src/cmd/compile/internal/amd64/ggen.go b/src/cmd/compile/internal/amd64/ggen.go
index 14c3bd1129..259a083f75 100644
--- a/src/cmd/compile/internal/amd64/ggen.go
+++ b/src/cmd/compile/internal/amd64/ggen.go
@@ -85,7 +85,7 @@ func zerorange(pp *objw.Progs, p *obj.Prog, off, cnt int64, state *uint32) *obj.
 		}
 		p = pp.Append(p, x86.AMOVQ, obj.TYPE_REG, x86.REG_AX, 0, obj.TYPE_MEM, x86.REG_SP, off)
 	} else if !isPlan9 && cnt <= int64(8*types.RegSize) {
-		if objabi.Regabi_enabled == 0 && *state&x15 == 0 {
+		if !objabi.Experiment.RegabiG && *state&x15 == 0 {
 			p = pp.Append(p, x86.AXORPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_REG, x86.REG_X15, 0)
 			*state |= x15
 		}
@@ -98,7 +98,7 @@ func zerorange(pp *objw.Progs, p *obj.Prog, off, cnt int64, state *uint32) *obj.
 			p = pp.Append(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_MEM, x86.REG_SP, off+cnt-int64(16))
 		}
 	} else if !isPlan9 && (cnt <= int64(128*types.RegSize)) {
-		if objabi.Regabi_enabled == 0 && *state&x15 == 0 {
+		if !objabi.Experiment.RegabiG && *state&x15 == 0 {
 			p = pp.Append(p, x86.AXORPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_REG, x86.REG_X15, 0)
 			*state |= x15
 		}
diff --git a/src/cmd/compile/internal/amd64/ssa.go b/src/cmd/compile/internal/amd64/ssa.go
index 3798c37b34..bdd9da77b0 100644
--- a/src/cmd/compile/internal/amd64/ssa.go
+++ b/src/cmd/compile/internal/amd64/ssa.go
@@ -827,8 +827,8 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		if s.ABI != obj.ABIInternal {
 			v.Fatalf("MOVOstorezero can be only used in ABIInternal functions")
 		}
-		if !(objabi.Regabi_enabled == 1 && base.Flag.ABIWrap) {
-			// zeroing X15 manually if wrappers are not used
+		if !objabi.Experiment.RegabiG {
+			// zero X15 manually
 			opregreg(s, x86.AXORPS, x86.REG_X15, x86.REG_X15)
 		}
 		p := s.Prog(v.Op.Asm())
@@ -921,8 +921,8 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		if s.ABI != obj.ABIInternal {
 			v.Fatalf("MOVOconst can be only used in ABIInternal functions")
 		}
-		if !(objabi.Regabi_enabled == 1 && base.Flag.ABIWrap) {
-			// zeroing X15 manually if wrappers are not used
+		if !objabi.Experiment.RegabiG {
+			// zero X15 manually
 			opregreg(s, x86.AXORPS, x86.REG_X15, x86.REG_X15)
 		}
 		off := duffStart(v.AuxInt)
@@ -1004,20 +1004,20 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		// Closure pointer is DX.
 		ssagen.CheckLoweredGetClosurePtr(v)
 	case ssa.OpAMD64LoweredGetG:
-		if objabi.Regabi_enabled == 1 && base.Flag.ABIWrap {
+		if objabi.Experiment.RegabiG {
 			v.Fatalf("LoweredGetG should not appear in new ABI")
 		}
 		r := v.Reg()
 		getgFromTLS(s, r)
 	case ssa.OpAMD64CALLstatic:
-		if objabi.Regabi_enabled == 1 && s.ABI == obj.ABI0 && v.Aux.(*ssa.AuxCall).Fn.ABI() == obj.ABIInternal {
+		if objabi.Experiment.RegabiG && s.ABI == obj.ABI0 && v.Aux.(*ssa.AuxCall).Fn.ABI() == obj.ABIInternal {
 			// zeroing X15 when entering ABIInternal from ABI0
 			opregreg(s, x86.AXORPS, x86.REG_X15, x86.REG_X15)
 			// set G register from TLS
 			getgFromTLS(s, x86.REG_R14)
 		}
 		s.Call(v)
-		if objabi.Regabi_enabled == 1 && s.ABI == obj.ABIInternal && v.Aux.(*ssa.AuxCall).Fn.ABI() == obj.ABI0 {
+		if objabi.Experiment.RegabiG && s.ABI == obj.ABIInternal && v.Aux.(*ssa.AuxCall).Fn.ABI() == obj.ABI0 {
 			// zeroing X15 when entering ABIInternal from ABI0
 			opregreg(s, x86.AXORPS, x86.REG_X15, x86.REG_X15)
 			// set G register from TLS
@@ -1304,7 +1304,7 @@ func ssaGenBlock(s *ssagen.State, b, next *ssa.Block) {
 	case ssa.BlockRet:
 		s.Prog(obj.ARET)
 	case ssa.BlockRetJmp:
-		if objabi.Regabi_enabled == 1 && s.ABI == obj.ABI0 && b.Aux.(*obj.LSym).ABI() == obj.ABIInternal {
+		if objabi.Experiment.RegabiG && s.ABI == obj.ABI0 && b.Aux.(*obj.LSym).ABI() == obj.ABIInternal {
 			// zeroing X15 when entering ABIInternal from ABI0
 			opregreg(s, x86.AXORPS, x86.REG_X15, x86.REG_X15)
 			// set G register from TLS
diff --git a/src/cmd/compile/internal/base/flag.go b/src/cmd/compile/internal/base/flag.go
index 1087f97d07..959fededa9 100644
--- a/src/cmd/compile/internal/base/flag.go
+++ b/src/cmd/compile/internal/base/flag.go
@@ -82,7 +82,6 @@ type CmdFlags struct {
 	CompilingRuntime bool "flag:\"+\" help:\"compiling runtime\""
 
 	// Longer names
-	ABIWrap            bool         "help:\"enable generation of ABI wrappers\""
 	ABIWrapLimit       int          "help:\"emit at most N ABI wrappers (for debugging)\""
 	AsmHdr             string       "help:\"write assembly header to `file`\""
 	Bench              string       "help:\"append benchmark times to `file`\""
@@ -147,7 +146,6 @@ func ParseFlags() {
 	Flag.LowerP = &Ctxt.Pkgpath
 	Flag.LowerV = &Ctxt.Debugvlog
 
-	Flag.ABIWrap = objabi.Regabi_enabled != 0
 	Flag.Dwarf = objabi.GOARCH != "wasm"
 	Flag.DwarfBASEntries = &Ctxt.UseBASEntries
 	Flag.DwarfLocationLists = &Ctxt.Flag_locationlists
diff --git a/src/cmd/compile/internal/ssa/config.go b/src/cmd/compile/internal/ssa/config.go
index 9921b51cc7..75fa71ce35 100644
--- a/src/cmd/compile/internal/ssa/config.go
+++ b/src/cmd/compile/internal/ssa/config.go
@@ -6,7 +6,6 @@ package ssa
 
 import (
 	"cmd/compile/internal/abi"
-	"cmd/compile/internal/base"
 	"cmd/compile/internal/ir"
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
@@ -204,7 +203,7 @@ func NewConfig(arch string, types Types, ctxt *obj.Link, optimize bool) *Config
 		c.floatParamRegs = paramFloatRegAMD64
 		c.FPReg = framepointerRegAMD64
 		c.LinkReg = linkRegAMD64
-		c.hasGReg = base.Flag.ABIWrap
+		c.hasGReg = objabi.Experiment.RegabiG
 	case "386":
 		c.PtrSize = 4
 		c.RegSize = 4
diff --git a/src/cmd/compile/internal/ssa/gen/AMD64.rules b/src/cmd/compile/internal/ssa/gen/AMD64.rules
index bece886c0d..7dc381bd81 100644
--- a/src/cmd/compile/internal/ssa/gen/AMD64.rules
+++ b/src/cmd/compile/internal/ssa/gen/AMD64.rules
@@ -460,7 +460,7 @@
 (IsInBounds idx len) => (SETB (CMPQ idx len))
 (IsSliceInBounds idx len) => (SETBE (CMPQ idx len))
 (NilCheck ...) => (LoweredNilCheck ...)
-(GetG mem) && !(objabi.Regabi_enabled == 1 && base.Flag.ABIWrap) => (LoweredGetG mem) // only lower in old ABI. in new ABI we have a G register.
+(GetG mem) && !objabi.Experiment.RegabiG => (LoweredGetG mem) // only lower in old ABI. in new ABI we have a G register.
 (GetClosurePtr ...) => (LoweredGetClosurePtr ...)
 (GetCallerPC ...) => (LoweredGetCallerPC ...)
 (GetCallerSP ...) => (LoweredGetCallerSP ...)
diff --git a/src/cmd/compile/internal/ssa/rewriteAMD64.go b/src/cmd/compile/internal/ssa/rewriteAMD64.go
index ac5bf9d928..36f872d0c4 100644
--- a/src/cmd/compile/internal/ssa/rewriteAMD64.go
+++ b/src/cmd/compile/internal/ssa/rewriteAMD64.go
@@ -5,7 +5,6 @@ package ssa
 
 import "math"
 import "cmd/internal/objabi"
-import "cmd/compile/internal/base"
 import "cmd/compile/internal/types"
 
 func rewriteValueAMD64(v *Value) bool {
@@ -30273,11 +30272,11 @@ func rewriteValueAMD64_OpFloor(v *Value) bool {
 func rewriteValueAMD64_OpGetG(v *Value) bool {
 	v_0 := v.Args[0]
 	// match: (GetG mem)
-	// cond: !(objabi.Regabi_enabled == 1 && base.Flag.ABIWrap)
+	// cond: !objabi.Experiment.RegabiG
 	// result: (LoweredGetG mem)
 	for {
 		mem := v_0
-		if !(!(objabi.Regabi_enabled == 1 && base.Flag.ABIWrap)) {
+		if !(!objabi.Experiment.RegabiG) {
 			break
 		}
 		v.reset(OpAMD64LoweredGetG)
diff --git a/src/cmd/compile/internal/ssagen/abi.go b/src/cmd/compile/internal/ssagen/abi.go
index e3f3ac637b..6d391ed9f7 100644
--- a/src/cmd/compile/internal/ssagen/abi.go
+++ b/src/cmd/compile/internal/ssagen/abi.go
@@ -24,7 +24,7 @@ import (
 // useNewABIWrapGen returns TRUE if the compiler should generate an
 // ABI wrapper for the function 'f'.
 func useABIWrapGen(f *ir.Func) bool {
-	if !base.Flag.ABIWrap {
+	if !objabi.Experiment.RegabiWrappers {
 		return false
 	}
 
@@ -140,7 +140,7 @@ func ReadSymABIs(file, myimportpath string) {
 func InitLSym(f *ir.Func, hasBody bool) {
 	// FIXME: for new-style ABI wrappers, we set up the lsym at the
 	// point the wrapper is created.
-	if f.LSym != nil && base.Flag.ABIWrap {
+	if f.LSym != nil && objabi.Experiment.RegabiWrappers {
 		return
 	}
 	staticdata.NeedFuncSym(f.Sym())
diff --git a/src/cmd/compile/internal/ssagen/ssa.go b/src/cmd/compile/internal/ssagen/ssa.go
index 293062b8ec..e97535e748 100644
--- a/src/cmd/compile/internal/ssagen/ssa.go
+++ b/src/cmd/compile/internal/ssagen/ssa.go
@@ -261,8 +261,7 @@ func regAbiForFuncType(ft *types.Func) bool {
 }
 
 func regabiEnabledForAllCompilation() bool {
-	// TODO compiler does not yet change behavior for GOEXPERIMENT=regabi
-	return false && objabi.Regabi_enabled != 0
+	return objabi.Experiment.RegabiArgs
 }
 
 // getParam returns the Field of ith param of node n (which is a
@@ -7448,7 +7447,7 @@ func clobberBase(n ir.Node) ir.Node {
 //
 func callTargetLSym(callee *ir.Name, callerLSym *obj.LSym) *obj.LSym {
 	lsym := callee.Linksym()
-	if !base.Flag.ABIWrap {
+	if !objabi.Experiment.RegabiWrappers {
 		return lsym
 	}
 	fn := callee.Func