cmd/compile: remove ld/st-followed nil checks for PPC64

Enabled checks (except for DUFF-ops which aren't implemented yet).
Added ppc64le to relevant test.

Also updated register list to reflect no-longer-reserved-
for-constants status (file was missed in that change).

Updates #16010.

Change-Id: I31b1aac19e14994f760f2ecd02edbeb1f78362e7
Reviewed-on: https://go-review.googlesource.com/28548
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/compile/internal/ppc64/ssa.go

@@ -73,11 +73,11 @@ var ssaRegToReg = []int16{
 	ppc64.REG_F24,
 	ppc64.REG_F25,
 	ppc64.REG_F26,
-	// ppc64.REG_F27, // reserved for "floating conversion constant"
-	// ppc64.REG_F28, // 0.0
-	// ppc64.REG_F29, // 0.5
-	// ppc64.REG_F30, // 1.0
-	// ppc64.REG_F31, // 2.0
+	ppc64.REG_F27,
+	ppc64.REG_F28,
+	ppc64.REG_F29,
+	ppc64.REG_F30,
+	ppc64.REG_F31,
 
 	// ppc64.REG_CR0,
 	// ppc64.REG_CR1,
@@ -94,6 +94,10 @@ var ssaRegToReg = []int16{
 	// ppc64.REG_CTR,
 }
 
+// Smallest possible faulting page at address zero,
+// see ../../../../runtime/mheap.go:/minPhysPageSize
+const minZeroPage = 4096
+
 var condOps = map[ssa.Op]obj.As{
 	ssa.OpPPC64Equal:        ppc64.ABEQ,
 	ssa.OpPPC64NotEqual:     ppc64.ABNE,
@@ -848,61 +852,62 @@ func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
 	case ssa.OpPPC64LoweredNilCheck:
 		// Optimization - if the subsequent block has a load or store
 		// at the same address, we don't need to issue this instruction.
-		// mem := v.Args[1]
-		// for _, w := range v.Block.Succs[0].Block().Values {
-		// 	if w.Op == ssa.OpPhi {
-		// 		if w.Type.IsMemory() {
-		// 			mem = w
-		// 		}
-		// 		continue
-		// 	}
-		// 	if len(w.Args) == 0 || !w.Args[len(w.Args)-1].Type.IsMemory() {
-		// 		// w doesn't use a store - can't be a memory op.
-		// 		continue
-		// 	}
-		// 	if w.Args[len(w.Args)-1] != mem {
-		// 		v.Fatalf("wrong store after nilcheck v=%s w=%s", v, w)
-		// 	}
-		// 	switch w.Op {
-		// 	case ssa.OpPPC64MOVBload, ssa.OpPPC64MOVBUload, ssa.OpPPC64MOVHload, ssa.OpPPC64MOVHUload,
-		// 		ssa.OpPPC64MOVWload, ssa.OpPPC64MOVFload, ssa.OpPPC64MOVDload,
-		// 		ssa.OpPPC64MOVBstore, ssa.OpPPC64MOVHstore, ssa.OpPPC64MOVWstore,
-		// 		ssa.OpPPC64MOVFstore, ssa.OpPPC64MOVDstore:
-		// 		// arg0 is ptr, auxint is offset
-		// 		if w.Args[0] == v.Args[0] && w.Aux == nil && w.AuxInt >= 0 && w.AuxInt < minZeroPage {
-		// 			if gc.Debug_checknil != 0 && int(v.Line) > 1 {
-		// 				gc.Warnl(v.Line, "removed nil check")
-		// 			}
-		// 			return
-		// 		}
-		// 	case ssa.OpPPC64DUFFZERO, ssa.OpPPC64LoweredZero, ssa.OpPPC64LoweredZeroU:
-		// 		// arg0 is ptr
-		// 		if w.Args[0] == v.Args[0] {
-		// 			if gc.Debug_checknil != 0 && int(v.Line) > 1 {
-		// 				gc.Warnl(v.Line, "removed nil check")
-		// 			}
-		// 			return
-		// 		}
-		// 	case ssa.OpPPC64DUFFCOPY, ssa.OpPPC64LoweredMove, ssa.OpPPC64LoweredMoveU:
-		// 		// arg0 is dst ptr, arg1 is src ptr
-		// 		if w.Args[0] == v.Args[0] || w.Args[1] == v.Args[0] {
-		// 			if gc.Debug_checknil != 0 && int(v.Line) > 1 {
-		// 				gc.Warnl(v.Line, "removed nil check")
-		// 			}
-		// 			return
-		// 		}
-		// 	default:
-		// 	}
-		// 	if w.Type.IsMemory() {
-		// 		if w.Op == ssa.OpVarDef || w.Op == ssa.OpVarKill || w.Op == ssa.OpVarLive {
-		// 			// these ops are OK
-		// 			mem = w
-		// 			continue
-		// 		}
-		// 		// We can't delay the nil check past the next store.
-		// 		break
-		// 	}
-		// }
+		mem := v.Args[1]
+		for _, w := range v.Block.Succs[0].Block().Values {
+			if w.Op == ssa.OpPhi {
+				if w.Type.IsMemory() {
+					mem = w
+				}
+				continue
+			}
+			if len(w.Args) == 0 || !w.Args[len(w.Args)-1].Type.IsMemory() {
+				// w doesn't use a store - can't be a memory op.
+				continue
+			}
+			if w.Args[len(w.Args)-1] != mem {
+				v.Fatalf("wrong store after nilcheck v=%s w=%s", v, w)
+			}
+			switch w.Op {
+			case ssa.OpPPC64MOVBload, ssa.OpPPC64MOVBZload, ssa.OpPPC64MOVHload, ssa.OpPPC64MOVHZload,
+				ssa.OpPPC64MOVWload, ssa.OpPPC64MOVWZload, ssa.OpPPC64MOVDload, ssa.OpPPC64FMOVDload, ssa.OpPPC64FMOVSload,
+				ssa.OpPPC64MOVBstore, ssa.OpPPC64MOVHstore, ssa.OpPPC64MOVWstore,
+				ssa.OpPPC64MOVDstore, ssa.OpPPC64FMOVSstore, ssa.OpPPC64FMOVDstore,
+				ssa.OpPPC64MOVDstorezero, ssa.OpPPC64MOVWstorezero, ssa.OpPPC64MOVHstorezero, ssa.OpPPC64MOVBstorezero:
+				// arg0 is ptr, auxint is offset
+				if w.Args[0] == v.Args[0] && w.Aux == nil && w.AuxInt >= 0 && w.AuxInt < minZeroPage {
+					if gc.Debug_checknil != 0 && int(v.Line) > 1 {
+						gc.Warnl(v.Line, "removed nil check")
+					}
+					return
+				}
+			case ssa.OpPPC64LoweredZero: // ssa.OpPPC64DUFFZERO,
+				// arg0 is ptr
+				if w.Args[0] == v.Args[0] {
+					if gc.Debug_checknil != 0 && int(v.Line) > 1 {
+						gc.Warnl(v.Line, "removed nil check")
+					}
+					return
+				}
+			case ssa.OpPPC64LoweredMove: // ssa.OpPPC64DUFFCOPY,
+				// arg0 is dst ptr, arg1 is src ptr
+				if w.Args[0] == v.Args[0] || w.Args[1] == v.Args[0] {
+					if gc.Debug_checknil != 0 && int(v.Line) > 1 {
+						gc.Warnl(v.Line, "removed nil check")
+					}
+					return
+				}
+			default:
+			}
+			if w.Type.IsMemory() {
+				if w.Op == ssa.OpVarDef || w.Op == ssa.OpVarKill || w.Op == ssa.OpVarLive {
+					// these ops are OK
+					mem = w
+					continue
+				}
+				// We can't delay the nil check past the next store.
+				break
+			}
+		}
 		// Issue a load which will fault if arg is nil.
 		p := gc.Prog(ppc64.AMOVB)
 		p.From.Type = obj.TYPE_MEM

test/nilptr3_ssa.go

 // errorcheck -0 -d=nil
-// +build amd64 arm amd64p32 386 arm64 mips64 mips64le
+// +build amd64 arm amd64p32 386 arm64 mips64 mips64le ppc64le
 
 // Copyright 2013 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style