From: Russ Cox <rsc@golang.org>
Date: Wed, 5 Mar 2025 04:45:38 +0000 (-0500)
Subject: cmd/compile: use FMA on plan9, and drop UseFMA
X-Git-Tag: go1.25rc1~740
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=c9b07e887169f661b9cea2ff16cbb4642d2622dc;p=gostls13.git

cmd/compile: use FMA on plan9, and drop UseFMA

Every OS uses FMA now.

Change-Id: Ia7ffa77c52c45aefca611ddc54e9dfffb27a48da
Reviewed-on: https://go-review.googlesource.com/c/go/+/655877
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Russ Cox <rsc@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
---

diff --git a/src/cmd/compile/internal/ssa/config.go b/src/cmd/compile/internal/ssa/config.go
index 607a3936f2..cf881ee078 100644
--- a/src/cmd/compile/internal/ssa/config.go
+++ b/src/cmd/compile/internal/ssa/config.go
@@ -11,7 +11,6 @@ import (
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
 	"cmd/internal/src"
-	"internal/buildcfg"
 )
 
 // A Config holds readonly compilation information.
@@ -48,7 +47,6 @@ type Config struct {
 	SoftFloat      bool      //
 	Race           bool      // race detector enabled
 	BigEndian      bool      //
-	UseFMA         bool      // Use hardware FMA operation
 	unalignedOK    bool      // Unaligned loads/stores are ok
 	haveBswap64    bool      // architecture implements Bswap64
 	haveBswap32    bool      // architecture implements Bswap32
@@ -354,7 +352,6 @@ func NewConfig(arch string, types Types, ctxt *obj.Link, optimize, softfloat boo
 	}
 	c.ctxt = ctxt
 	c.optimize = optimize
-	c.UseFMA = true
 	c.SoftFloat = softfloat
 	if softfloat {
 		c.floatParamRegs = nil // no FP registers in softfloat mode
@@ -363,12 +360,6 @@ func NewConfig(arch string, types Types, ctxt *obj.Link, optimize, softfloat boo
 	c.ABI0 = abi.NewABIConfig(0, 0, ctxt.Arch.FixedFrameSize, 0)
 	c.ABI1 = abi.NewABIConfig(len(c.intParamRegs), len(c.floatParamRegs), ctxt.Arch.FixedFrameSize, 1)
 
-	// On Plan 9, floating point operations are not allowed in note handler.
-	if buildcfg.GOOS == "plan9" {
-		// Don't use FMA on Plan 9
-		c.UseFMA = false
-	}
-
 	if ctxt.Flag_shared {
 		// LoweredWB is secretly a CALL and CALLs on 386 in
 		// shared mode get rewritten by obj6.go to go through
diff --git a/src/cmd/compile/internal/ssa/func.go b/src/cmd/compile/internal/ssa/func.go
index 12e4c268f0..51c5ec5f04 100644
--- a/src/cmd/compile/internal/ssa/func.go
+++ b/src/cmd/compile/internal/ssa/func.go
@@ -832,9 +832,6 @@ func (f *Func) spSb() (sp, sb *Value) {
 // useFMA allows targeted debugging w/ GOFMAHASH
 // If you have an architecture-dependent FP glitch, this will help you find it.
 func (f *Func) useFMA(v *Value) bool {
-	if !f.Config.UseFMA {
-		return false
-	}
 	if base.FmaHash == nil {
 		return true
 	}
diff --git a/src/cmd/compile/internal/ssagen/intrinsics.go b/src/cmd/compile/internal/ssagen/intrinsics.go
index 4f84b6b924..7a234a5b2e 100644
--- a/src/cmd/compile/internal/ssagen/intrinsics.go
+++ b/src/cmd/compile/internal/ssagen/intrinsics.go
@@ -767,11 +767,6 @@ func initIntrinsics(cfg *intrinsicBuildConfig) {
 		sys.ARM64, sys.Loong64, sys.PPC64, sys.RISCV64, sys.S390X)
 	addF("math", "FMA",
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
-			if !s.config.UseFMA {
-				s.vars[n] = s.callResult(n, callNormal) // types.Types[TFLOAT64]
-				return s.variable(n, types.Types[types.TFLOAT64])
-			}
-
 			if cfg.goamd64 >= 3 {
 				return s.newValue3(ssa.OpFMA, types.Types[types.TFLOAT64], args[0], args[1], args[2])
 			}
@@ -804,10 +799,6 @@ func initIntrinsics(cfg *intrinsicBuildConfig) {
 		sys.AMD64)
 	addF("math", "FMA",
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
-			if !s.config.UseFMA {
-				s.vars[n] = s.callResult(n, callNormal) // types.Types[TFLOAT64]
-				return s.variable(n, types.Types[types.TFLOAT64])
-			}
 			addr := s.entryNewValue1A(ssa.OpAddr, types.Types[types.TBOOL].PtrTo(), ir.Syms.ARMHasVFPv4, s.sb)
 			v := s.load(types.Types[types.TBOOL], addr)
 			b := s.endBlock()