be: Specify emit => "" instead of manually setting be_emit_nothing.

ir/be/amd64/amd64_emitter.c

@@ -746,7 +746,6 @@ static void amd64_register_emitters(void)
 	be_set_emitter(op_amd64_Jmp,       emit_amd64_Jmp);
 	be_set_emitter(op_amd64_Mov,       emit_amd64_Mov);
 	be_set_emitter(op_amd64_Return,    emit_amd64_Return);
-	be_set_emitter(op_amd64_Start,     be_emit_nothing);
 	be_set_emitter(op_amd64_SwitchJmp, emit_amd64_SwitchJmp);
 	be_set_emitter(op_be_Copy,         emit_be_Copy);
 	be_set_emitter(op_be_CopyKeep,     emit_be_Copy);

ir/be/amd64/amd64_spec.pl

@@ -469,6 +469,7 @@ Start => {
 	out_arity => "variable",
 	ins       => [],
 	fixed     => "amd64_op_mode_t op_mode = AMD64_OP_NONE;\n",
+	emit      => "",
 },
 
 Return => {

ir/be/arm/arm_emitter.c

@@ -690,7 +690,6 @@ static void arm_register_emitters(void)
 	be_set_emitter(op_arm_fConst,    emit_arm_fConst);
 	be_set_emitter(op_arm_FrameAddr, emit_arm_FrameAddr);
 	be_set_emitter(op_arm_Jmp,       emit_arm_Jmp);
-	be_set_emitter(op_arm_Start,     be_emit_nothing);
 	be_set_emitter(op_arm_SwitchJmp, emit_arm_SwitchJmp);
 	be_set_emitter(op_be_Copy,       emit_be_Copy);
 	be_set_emitter(op_be_CopyKeep,   emit_be_Copy);

ir/be/arm/arm_spec.pl

@@ -698,6 +698,7 @@ Start => {
 	state     => "pinned",
 	out_arity => "variable",
 	ins       => [],
+	emit      => "",
 },
 
 Return => {

ir/be/ia32/ia32_emitter.c

@@ -1366,7 +1366,6 @@ static void ia32_register_emitters(void)
 	be_set_emitter(op_be_IncSP,        emit_be_IncSP);
 	be_set_emitter(op_be_Perm,         emit_be_Perm);
 	be_set_emitter(op_ia32_Return,     emit_ia32_Return);
-	be_set_emitter(op_ia32_Start,      be_emit_nothing);
 	be_set_emitter(op_ia32_Asm,        emit_ia32_Asm);
 	be_set_emitter(op_ia32_ClimbFrame, emit_ia32_ClimbFrame);
 	be_set_emitter(op_ia32_CMovcc,     emit_ia32_CMovcc);
@@ -3325,11 +3324,6 @@ static void ia32_register_binary_emitters(void)
 	be_set_emitter(op_ia32_fst,           bemit_fst);
 	be_set_emitter(op_ia32_fsub,          bemit_fsub);
 	be_set_emitter(op_ia32_fxch,          bemit_fxch);
-
-	/* ignore the following nodes */
-	be_set_emitter(op_ia32_ProduceVal, be_emit_nothing);
-	be_set_emitter(op_ia32_Start,      be_emit_nothing);
-	be_set_emitter(op_ia32_Unknown,    be_emit_nothing);
 }
 
 static void gen_binary_block(ir_node *block)

ir/be/ia32/ia32_spec.pl

@@ -1218,6 +1218,7 @@ Start => {
 	out_arity => "variable",
 	ins       => [],
 	latency   => 0,
+	emit      => "",
 },
 
 Return => {

ir/be/sparc/sparc_emitter.c

@@ -1378,9 +1378,6 @@ static void sparc_register_emitters(void)
 	be_set_emitter(op_sparc_SwitchJmp, emit_sparc_SwitchJmp);
 	be_set_emitter(op_sparc_UDiv,      emit_sparc_UDiv);
 	be_set_emitter(op_sparc_fbfcc,     emit_sparc_fbfcc);
-
-	/* no need to emit anything for the following nodes */
-	be_set_emitter(op_sparc_Start, be_emit_nothing);
 }
 
 static bool block_needs_label(const ir_node *block, const ir_node *sched_prev)

ir/be/sparc/sparc_spec.pl

@@ -503,6 +503,7 @@ Start => {
 	state     => "pinned",
 	out_arity => "variable",
 	ins       => [],
+	emit      => "",
 },
 
 # This is a Jump instruction, but with the addition that you can add custom