cmd/compile: move s390x over to new bounds check strategy

Change-Id: I86ed1a60165b729bb88a8a418da0ea1b59b3dc10
Reviewed-on: https://go-review.googlesource.com/c/go/+/682499
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Mauri de Souza Meneguzzo <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: Michael Munday <[email protected]>
Reviewed-by: Mark Freeman <[email protected]>

Author: randall77

src/cmd/compile/internal/s390x/ssa.go

@@ -15,6 +15,7 @@ import (
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
 	"cmd/internal/obj/s390x"
+	"internal/abi"
 )
 
 // ssaMarkMoves marks any MOVXconst ops that need to avoid clobbering flags.
@@ -573,12 +574,92 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p.To.Name = obj.NAME_EXTERN
 		// AuxInt encodes how many buffer entries we need.
 		p.To.Sym = ir.Syms.GCWriteBarrier[v.AuxInt-1]
-	case ssa.OpS390XLoweredPanicBoundsA, ssa.OpS390XLoweredPanicBoundsB, ssa.OpS390XLoweredPanicBoundsC:
-		p := s.Prog(obj.ACALL)
+
+	case ssa.OpS390XLoweredPanicBoundsRR, ssa.OpS390XLoweredPanicBoundsRC, ssa.OpS390XLoweredPanicBoundsCR, ssa.OpS390XLoweredPanicBoundsCC:
+		// Compute the constant we put in the PCData entry for this call.
+		code, signed := ssa.BoundsKind(v.AuxInt).Code()
+		xIsReg := false
+		yIsReg := false
+		xVal := 0
+		yVal := 0
+		switch v.Op {
+		case ssa.OpS390XLoweredPanicBoundsRR:
+			xIsReg = true
+			xVal = int(v.Args[0].Reg() - s390x.REG_R0)
+			yIsReg = true
+			yVal = int(v.Args[1].Reg() - s390x.REG_R0)
+		case ssa.OpS390XLoweredPanicBoundsRC:
+			xIsReg = true
+			xVal = int(v.Args[0].Reg() - s390x.REG_R0)
+			c := v.Aux.(ssa.PanicBoundsC).C
+			if c >= 0 && c <= abi.BoundsMaxConst {
+				yVal = int(c)
+			} else {
+				// Move constant to a register
+				yIsReg = true
+				if yVal == xVal {
+					yVal = 1
+				}
+				p := s.Prog(s390x.AMOVD)
+				p.From.Type = obj.TYPE_CONST
+				p.From.Offset = c
+				p.To.Type = obj.TYPE_REG
+				p.To.Reg = s390x.REG_R0 + int16(yVal)
+			}
+		case ssa.OpS390XLoweredPanicBoundsCR:
+			yIsReg = true
+			yVal := int(v.Args[0].Reg() - s390x.REG_R0)
+			c := v.Aux.(ssa.PanicBoundsC).C
+			if c >= 0 && c <= abi.BoundsMaxConst {
+				xVal = int(c)
+			} else {
+				// Move constant to a register
+				if xVal == yVal {
+					xVal = 1
+				}
+				p := s.Prog(s390x.AMOVD)
+				p.From.Type = obj.TYPE_CONST
+				p.From.Offset = c
+				p.To.Type = obj.TYPE_REG
+				p.To.Reg = s390x.REG_R0 + int16(xVal)
+			}
+		case ssa.OpS390XLoweredPanicBoundsCC:
+			c := v.Aux.(ssa.PanicBoundsCC).Cx
+			if c >= 0 && c <= abi.BoundsMaxConst {
+				xVal = int(c)
+			} else {
+				// Move constant to a register
+				xIsReg = true
+				p := s.Prog(s390x.AMOVD)
+				p.From.Type = obj.TYPE_CONST
+				p.From.Offset = c
+				p.To.Type = obj.TYPE_REG
+				p.To.Reg = s390x.REG_R0 + int16(xVal)
+			}
+			c = v.Aux.(ssa.PanicBoundsCC).Cy
+			if c >= 0 && c <= abi.BoundsMaxConst {
+				yVal = int(c)
+			} else {
+				// Move constant to a register
+				yIsReg = true
+				yVal = 1
+				p := s.Prog(s390x.AMOVD)
+				p.From.Type = obj.TYPE_CONST
+				p.From.Offset = c
+				p.To.Type = obj.TYPE_REG
+				p.To.Reg = s390x.REG_R0 + int16(yVal)
+			}
+		}
+		c := abi.BoundsEncode(code, signed, xIsReg, yIsReg, xVal, yVal)
+
+		p := s.Prog(obj.APCDATA)
+		p.From.SetConst(abi.PCDATA_PanicBounds)
+		p.To.SetConst(int64(c))
+		p = s.Prog(obj.ACALL)
 		p.To.Type = obj.TYPE_MEM
 		p.To.Name = obj.NAME_EXTERN
-		p.To.Sym = ssagen.BoundsCheckFunc[v.AuxInt]
-		s.UseArgs(16) // space used in callee args area by assembly stubs
+		p.To.Sym = ir.Syms.PanicBounds
+
 	case ssa.OpS390XFLOGR, ssa.OpS390XPOPCNT,
 		ssa.OpS390XNEG, ssa.OpS390XNEGW,
 		ssa.OpS390XMOVWBR, ssa.OpS390XMOVDBR:

src/cmd/compile/internal/ssa/_gen/S390X.rules

@@ -458,9 +458,11 @@
 // Write barrier.
 (WB ...) => (LoweredWB ...)
 
-(PanicBounds [kind] x y mem) && boundsABI(kind) == 0 => (LoweredPanicBoundsA [kind] x y mem)
-(PanicBounds [kind] x y mem) && boundsABI(kind) == 1 => (LoweredPanicBoundsB [kind] x y mem)
-(PanicBounds [kind] x y mem) && boundsABI(kind) == 2 => (LoweredPanicBoundsC [kind] x y mem)
+(PanicBounds ...) => (LoweredPanicBoundsRR ...)
+(LoweredPanicBoundsRR [kind] x (MOVDconst [c]) mem) => (LoweredPanicBoundsRC [kind] x {PanicBoundsC{C:c}} mem)
+(LoweredPanicBoundsRR [kind] (MOVDconst [c]) y mem) => (LoweredPanicBoundsCR [kind] {PanicBoundsC{C:c}} y mem)
+(LoweredPanicBoundsRC [kind] {p} (MOVDconst [c]) mem) => (LoweredPanicBoundsCC [kind] {PanicBoundsCC{Cx:c, Cy:p.C}} mem)
+(LoweredPanicBoundsCR [kind] {p} (MOVDconst [c]) mem) => (LoweredPanicBoundsCC [kind] {PanicBoundsCC{Cx:p.C, Cy:c}} mem)
 
 // ***************************
 // Above: lowering rules

src/cmd/compile/internal/ssa/_gen/S390XOps.go

@@ -114,6 +114,7 @@ func init() {
 		sb  = buildReg("SB")
 		r0  = buildReg("R0")
 		tmp = buildReg("R11") // R11 is used as a temporary in a small number of instructions.
+		lr  = buildReg("R14")
 
 		// R10 is reserved by the assembler.
 		gp   = buildReg("R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R11 R12 R14")
@@ -518,12 +519,15 @@ func init() {
 		// Returns a pointer to a write barrier buffer in R9.
 		{name: "LoweredWB", argLength: 1, reg: regInfo{clobbers: (callerSave &^ gpg) | buildReg("R14") | r1, outputs: []regMask{r9}}, clobberFlags: true, aux: "Int64"},
 
-		// There are three of these functions so that they can have three different register inputs.
-		// When we check 0 <= c <= cap (A), then 0 <= b <= c (B), then 0 <= a <= b (C), we want the
-		// default registers to match so we don't need to copy registers around unnecessarily.
-		{name: "LoweredPanicBoundsA", argLength: 3, aux: "Int64", reg: regInfo{inputs: []regMask{r2, r3}}, typ: "Mem", call: true}, // arg0=idx, arg1=len, arg2=mem, returns memory. AuxInt contains report code (see PanicBounds in generic.go).
-		{name: "LoweredPanicBoundsB", argLength: 3, aux: "Int64", reg: regInfo{inputs: []regMask{r1, r2}}, typ: "Mem", call: true}, // arg0=idx, arg1=len, arg2=mem, returns memory. AuxInt contains report code (see PanicBounds in generic.go).
-		{name: "LoweredPanicBoundsC", argLength: 3, aux: "Int64", reg: regInfo{inputs: []regMask{r0, r1}}, typ: "Mem", call: true}, // arg0=idx, arg1=len, arg2=mem, returns memory. AuxInt contains report code (see PanicBounds in generic.go).
+		// LoweredPanicBoundsRR takes x and y, two values that caused a bounds check to fail.
+		// the RC and CR versions are used when one of the arguments is a constant. CC is used
+		// when both are constant (normally both 0, as prove derives the fact that a [0] bounds
+		// failure means the length must have also been 0).
+		// AuxInt contains a report code (see PanicBounds in genericOps.go).
+		{name: "LoweredPanicBoundsRR", argLength: 3, aux: "Int64", reg: regInfo{inputs: []regMask{gp &^ lr, gp &^ lr}}, typ: "Mem", call: true}, // arg0=x, arg1=y, arg2=mem, returns memory.
+		{name: "LoweredPanicBoundsRC", argLength: 2, aux: "PanicBoundsC", reg: regInfo{inputs: []regMask{gp &^ lr}}, typ: "Mem", call: true},    // arg0=x, arg1=mem, returns memory.
+		{name: "LoweredPanicBoundsCR", argLength: 2, aux: "PanicBoundsC", reg: regInfo{inputs: []regMask{gp &^ lr}}, typ: "Mem", call: true},    // arg0=y, arg1=mem, returns memory.
+		{name: "LoweredPanicBoundsCC", argLength: 1, aux: "PanicBoundsCC", reg: regInfo{}, typ: "Mem", call: true},                              // arg0=mem, returns memory.
 
 		// Constant condition code values. The condition code can be 0, 1, 2 or 3.
 		{name: "FlagEQ"}, // CC=0 (equal)