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 <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Michael Pratt <[email protected]>

Author: 4a6f656c

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},