cmd/compile/internal: stop lowering OpConvert on riscv64

Lowering for OpConvert was removed for all architectures in CL#108496,
prior to the riscv64 port being upstreamed. Remove lowering of OpConvert
on riscv64, which brings it inline with all other architectures. This
results in 1,600+ instructions being removed from the riscv64 go binary.

Change-Id: Iaaf1f8b397875926604048b66ad8ac91a98c871e
Reviewed-on: https://go-review.googlesource.com/c/go/+/533335
Run-TryBot: Joel Sing <joel@sing.id.au>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>

src/cmd/compile/internal/riscv64/ssa.go

@@ -193,7 +193,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		// input args need no code
 	case ssa.OpPhi:
 		ssagen.CheckLoweredPhi(v)
-	case ssa.OpCopy, ssa.OpRISCV64MOVconvert, ssa.OpRISCV64MOVDreg:
+	case ssa.OpCopy, ssa.OpRISCV64MOVDreg:
 		if v.Type.IsMemory() {
 			return
 		}

src/cmd/compile/internal/ssa/_gen/RISCV64.rules

@@ -397,8 +397,6 @@
 		(ADD <ptr.Type> ptr (MOVDconst [s-moveSize(t.Alignment(), config)]))
 		mem)
 
-(Convert ...) => (MOVconvert ...)
-
 // Checks
 (IsNonNil ...) => (SNEZ ...)
 (IsInBounds ...) => (Less64U ...)

src/cmd/compile/internal/ssa/_gen/RISCV64Ops.go

@@ -233,12 +233,6 @@ func init() {
 		{name: "SLTU", argLength: 2, reg: gp21, asm: "SLTU"},                 // arg0 < arg1, unsigned, result is 0 or 1
 		{name: "SLTIU", argLength: 1, reg: gp11, asm: "SLTIU", aux: "Int64"}, // arg0 < auxint, unsigned, result is 0 or 1
 
-		// MOVconvert 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
-		// gets correctly ordered with respect to GC safepoints.
-		{name: "MOVconvert", argLength: 2, reg: gp11, asm: "MOV"}, // arg0, but converted to int/ptr as appropriate; arg1=mem
-
 		// Round ops to block fused-multiply-add extraction.
 		{name: "LoweredRound32F", argLength: 1, reg: fp11, resultInArg0: true},
 		{name: "LoweredRound64F", argLength: 1, reg: fp11, resultInArg0: true},

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

@@ -2401,7 +2401,6 @@ const (
 	OpRISCV64SLTI
 	OpRISCV64SLTU
 	OpRISCV64SLTIU
-	OpRISCV64MOVconvert
 	OpRISCV64LoweredRound32F
 	OpRISCV64LoweredRound64F
 	OpRISCV64CALLstatic
@@ -32222,19 +32221,6 @@ var opcodeTable = [...]opInfo{
 			},
 		},
 	},
-	{
-		name:   "MOVconvert",
-		argLen: 2,
-		asm:    riscv.AMOV,
-		reg: regInfo{
-			inputs: []inputInfo{
-				{0, 1006632944}, // X5 X6 X7 X8 X9 X10 X11 X12 X13 X14 X15 X16 X17 X18 X19 X20 X21 X22 X23 X24 X25 X26 X28 X29 X30
-			},
-			outputs: []outputInfo{
-				{0, 1006632944}, // X5 X6 X7 X8 X9 X10 X11 X12 X13 X14 X15 X16 X17 X18 X19 X20 X21 X22 X23 X24 X25 X26 X28 X29 X30
-			},
-		},
-	},
 	{
 		name:         "LoweredRound32F",
 		argLen:       1,

src/cmd/compile/internal/ssa/rewriteRISCV64.go

@@ -132,9 +132,6 @@ func rewriteValueRISCV64(v *Value) bool {
 		return rewriteValueRISCV64_OpConstBool(v)
 	case OpConstNil:
 		return rewriteValueRISCV64_OpConstNil(v)
-	case OpConvert:
-		v.Op = OpRISCV64MOVconvert
-		return true
 	case OpCopysign:
 		v.Op = OpRISCV64FSGNJD
 		return true