arch/powerpc/net/bpf_jit.h - kernel/msm - Gitiles

 /* bpf_jit.h: BPF JIT compiler for PPC64
  *
  * Copyright 2011 Matt Evans <matt@ozlabs.org>, IBM Corporation
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; version 2
  * of the License.
  */
 #ifndef _BPF_JIT_H
 #define _BPF_JIT_H

 #define BPF_PPC_STACK_LOCALS	32
 #define BPF_PPC_STACK_BASIC	(48+64)
 #define BPF_PPC_STACK_SAVE	(18*8)
 #define BPF_PPC_STACKFRAME	(BPF_PPC_STACK_BASIC+BPF_PPC_STACK_LOCALS+ \
 				 BPF_PPC_STACK_SAVE)
 #define BPF_PPC_SLOWPATH_FRAME	(48+64)

 /*
  * Generated code register usage:
  *
  * As normal PPC C ABI (e.g. r1=sp, r2=TOC), with:
  *
  * skb		r3	(Entry parameter)
  * A register	r4
  * X register	r5
  * addr param	r6
  * r7-r10	scratch
  * skb->data	r14
  * skb headlen	r15	(skb->len - skb->data_len)
  * m[0]		r16
  * m[...]	...
  * m[15]	r31
  */
 #define r_skb		3
 #define r_ret		3
 #define r_A		4
 #define r_X		5
 #define r_addr		6
 #define r_scratch1	7
 #define r_D		14
 #define r_HL		15
 #define r_M		16

 #ifndef __ASSEMBLY__

 /*
  * Assembly helpers from arch/powerpc/net/bpf_jit.S:
  */
 #define DECLARE_LOAD_FUNC(func)	\
 	extern u8 func[], func##_negative_offset[], func##_positive_offset[]

 DECLARE_LOAD_FUNC(sk_load_word);
 DECLARE_LOAD_FUNC(sk_load_half);
 DECLARE_LOAD_FUNC(sk_load_byte);
 DECLARE_LOAD_FUNC(sk_load_byte_msh);

 #define FUNCTION_DESCR_SIZE	24

 /*
  * 16-bit immediate helper macros: HA() is for use with sign-extending instrs
  * (e.g. LD, ADDI).  If the bottom 16 bits is "-ve", add another bit into the
  * top half to negate the effect (i.e. 0xffff + 1 = 0x(1)0000).
  */
 #define IMM_H(i)		((uintptr_t)(i)>>16)
 #define IMM_HA(i)		(((uintptr_t)(i)>>16) +			      \
 				 (((uintptr_t)(i) & 0x8000) >> 15))
 #define IMM_L(i)		((uintptr_t)(i) & 0xffff)

 #define PLANT_INSTR(d, idx, instr)					      \
 	do { if (d) { (d)[idx] = instr; } idx++; } while (0)
 #define EMIT(instr)		PLANT_INSTR(image, ctx->idx, instr)

 #define PPC_NOP()		EMIT(PPC_INST_NOP)
 #define PPC_BLR()		EMIT(PPC_INST_BLR)
 #define PPC_BLRL()		EMIT(PPC_INST_BLRL)
 #define PPC_MTLR(r)		EMIT(PPC_INST_MTLR | __PPC_RT(r))
 #define PPC_ADDI(d, a, i)	EMIT(PPC_INST_ADDI | __PPC_RT(d) |	      \
 				     __PPC_RA(a) | IMM_L(i))
 #define PPC_MR(d, a)		PPC_OR(d, a, a)
 #define PPC_LI(r, i)		PPC_ADDI(r, 0, i)
 #define PPC_ADDIS(d, a, i)	EMIT(PPC_INST_ADDIS |			      \
 				     __PPC_RS(d) | __PPC_RA(a) | IMM_L(i))
 #define PPC_LIS(r, i)		PPC_ADDIS(r, 0, i)
 #define PPC_STD(r, base, i)	EMIT(PPC_INST_STD | __PPC_RS(r) |	      \
 				     __PPC_RA(base) | ((i) & 0xfffc))

 #define PPC_LD(r, base, i)	EMIT(PPC_INST_LD | __PPC_RT(r) |	      \
 				     __PPC_RA(base) | IMM_L(i))
 #define PPC_LWZ(r, base, i)	EMIT(PPC_INST_LWZ | __PPC_RT(r) |	      \
 				     __PPC_RA(base) | IMM_L(i))
 #define PPC_LHZ(r, base, i)	EMIT(PPC_INST_LHZ | __PPC_RT(r) |	      \
 				     __PPC_RA(base) | IMM_L(i))
 /* Convenience helpers for the above with 'far' offsets: */
 #define PPC_LD_OFFS(r, base, i) do { if ((i) < 32768) PPC_LD(r, base, i);     \
 		else {	PPC_ADDIS(r, base, IMM_HA(i));			      \
 			PPC_LD(r, r, IMM_L(i)); } } while(0)

 #define PPC_LWZ_OFFS(r, base, i) do { if ((i) < 32768) PPC_LWZ(r, base, i);   \
 		else {	PPC_ADDIS(r, base, IMM_HA(i));			      \
 			PPC_LWZ(r, r, IMM_L(i)); } } while(0)

 #define PPC_LHZ_OFFS(r, base, i) do { if ((i) < 32768) PPC_LHZ(r, base, i);   \
 		else {	PPC_ADDIS(r, base, IMM_HA(i));			      \
 			PPC_LHZ(r, r, IMM_L(i)); } } while(0)

 #define PPC_CMPWI(a, i)		EMIT(PPC_INST_CMPWI | __PPC_RA(a) | IMM_L(i))
 #define PPC_CMPDI(a, i)		EMIT(PPC_INST_CMPDI | __PPC_RA(a) | IMM_L(i))
 #define PPC_CMPLWI(a, i)	EMIT(PPC_INST_CMPLWI | __PPC_RA(a) | IMM_L(i))
 #define PPC_CMPLW(a, b)		EMIT(PPC_INST_CMPLW | __PPC_RA(a) | __PPC_RB(b))

 #define PPC_SUB(d, a, b)	EMIT(PPC_INST_SUB | __PPC_RT(d) |	      \
 				     __PPC_RB(a) | __PPC_RA(b))
 #define PPC_ADD(d, a, b)	EMIT(PPC_INST_ADD | __PPC_RT(d) |	      \
 				     __PPC_RA(a) | __PPC_RB(b))
 #define PPC_MUL(d, a, b)	EMIT(PPC_INST_MULLW | __PPC_RT(d) |	      \
 				     __PPC_RA(a) | __PPC_RB(b))
 #define PPC_MULHWU(d, a, b)	EMIT(PPC_INST_MULHWU | __PPC_RT(d) |	      \
 				     __PPC_RA(a) | __PPC_RB(b))
 #define PPC_MULI(d, a, i)	EMIT(PPC_INST_MULLI | __PPC_RT(d) |	      \
 				     __PPC_RA(a) | IMM_L(i))
 #define PPC_DIVWU(d, a, b)	EMIT(PPC_INST_DIVWU | __PPC_RT(d) |	      \
 				     __PPC_RA(a) | __PPC_RB(b))
 #define PPC_AND(d, a, b)	EMIT(PPC_INST_AND | __PPC_RA(d) |	      \
 				     __PPC_RS(a) | __PPC_RB(b))
 #define PPC_ANDI(d, a, i)	EMIT(PPC_INST_ANDI | __PPC_RA(d) |	      \
 				     __PPC_RS(a) | IMM_L(i))
 #define PPC_AND_DOT(d, a, b)	EMIT(PPC_INST_ANDDOT | __PPC_RA(d) |	      \
 				     __PPC_RS(a) | __PPC_RB(b))
 #define PPC_OR(d, a, b)		EMIT(PPC_INST_OR | __PPC_RA(d) |	      \
 				     __PPC_RS(a) | __PPC_RB(b))
 #define PPC_ORI(d, a, i)	EMIT(PPC_INST_ORI | __PPC_RA(d) |	      \
 				     __PPC_RS(a) | IMM_L(i))
 #define PPC_ORIS(d, a, i)	EMIT(PPC_INST_ORIS | __PPC_RA(d) |	      \
 				     __PPC_RS(a) | IMM_L(i))
 #define PPC_SLW(d, a, s)	EMIT(PPC_INST_SLW | __PPC_RA(d) |	      \
 				     __PPC_RS(a) | __PPC_RB(s))
 #define PPC_SRW(d, a, s)	EMIT(PPC_INST_SRW | __PPC_RA(d) |	      \
 				     __PPC_RS(a) | __PPC_RB(s))
 /* slwi = rlwinm Rx, Ry, n, 0, 31-n */
 #define PPC_SLWI(d, a, i)	EMIT(PPC_INST_RLWINM | __PPC_RA(d) |	      \
 				     __PPC_RS(a) | __PPC_SH(i) |	      \
 				     __PPC_MB(0) | __PPC_ME(31-(i)))
 /* srwi = rlwinm Rx, Ry, 32-n, n, 31 */
 #define PPC_SRWI(d, a, i)	EMIT(PPC_INST_RLWINM | __PPC_RA(d) |	      \
 				     __PPC_RS(a) | __PPC_SH(32-(i)) |	      \
 				     __PPC_MB(i) | __PPC_ME(31))
 /* sldi = rldicr Rx, Ry, n, 63-n */
 #define PPC_SLDI(d, a, i)	EMIT(PPC_INST_RLDICR | __PPC_RA(d) |	      \
 				     __PPC_RS(a) | __PPC_SH(i) |	      \
 				     __PPC_MB(63-(i)) | (((i) & 0x20) >> 4))
 #define PPC_NEG(d, a)		EMIT(PPC_INST_NEG | __PPC_RT(d) | __PPC_RA(a))

 /* Long jump; (unconditional 'branch') */
 #define PPC_JMP(dest)		EMIT(PPC_INST_BRANCH |			      \
 				     (((dest) - (ctx->idx * 4)) & 0x03fffffc))
 /* "cond" here covers BO:BI fields. */
 #define PPC_BCC_SHORT(cond, dest)	EMIT(PPC_INST_BRANCH_COND |	      \
 					     (((cond) & 0x3ff) << 16) |	      \
 					     (((dest) - (ctx->idx * 4)) &     \
 					      0xfffc))
 #define PPC_LI32(d, i)		do { PPC_LI(d, IMM_L(i));		      \
 		if ((u32)(uintptr_t)(i) >= 32768) {			      \
 			PPC_ADDIS(d, d, IMM_HA(i));			      \
 		} } while(0)
 #define PPC_LI64(d, i)		do {					      \
 		if (!((uintptr_t)(i) & 0xffffffff00000000ULL))		      \
 			PPC_LI32(d, i);					      \
 		else {							      \
 			PPC_LIS(d, ((uintptr_t)(i) >> 48));		      \
 			if ((uintptr_t)(i) & 0x0000ffff00000000ULL)	      \
 				PPC_ORI(d, d,				      \
 					((uintptr_t)(i) >> 32) & 0xffff);     \
 			PPC_SLDI(d, d, 32);				      \
 			if ((uintptr_t)(i) & 0x00000000ffff0000ULL)	      \
 				PPC_ORIS(d, d,				      \
 					 ((uintptr_t)(i) >> 16) & 0xffff);    \
 			if ((uintptr_t)(i) & 0x000000000000ffffULL)	      \
 				PPC_ORI(d, d, (uintptr_t)(i) & 0xffff);	      \
 		} } while (0);

 static inline bool is_nearbranch(int offset)
 {
 	return (offset < 32768) && (offset >= -32768);
 }

 /*
  * The fly in the ointment of code size changing from pass to pass is
  * avoided by padding the short branch case with a NOP.	 If code size differs
  * with different branch reaches we will have the issue of code moving from
  * one pass to the next and will need a few passes to converge on a stable
  * state.
  */
 #define PPC_BCC(cond, dest)	do {					      \
 		if (is_nearbranch((dest) - (ctx->idx * 4))) {		      \
 			PPC_BCC_SHORT(cond, dest);			      \
 			PPC_NOP();					      \
 		} else {						      \
 			/* Flip the 'T or F' bit to invert comparison */      \
 			PPC_BCC_SHORT(cond ^ COND_CMP_TRUE, (ctx->idx+2)*4);  \
 			PPC_JMP(dest);					      \
 		} } while(0)

 /* To create a branch condition, select a bit of cr0... */
 #define CR0_LT		0
 #define CR0_GT		1
 #define CR0_EQ		2
 /* ...and modify BO[3] */
 #define COND_CMP_TRUE	0x100
 #define COND_CMP_FALSE	0x000
 /* Together, they make all required comparisons: */
 #define COND_GT		(CR0_GT | COND_CMP_TRUE)
 #define COND_GE		(CR0_LT | COND_CMP_FALSE)
 #define COND_EQ		(CR0_EQ | COND_CMP_TRUE)
 #define COND_NE		(CR0_EQ | COND_CMP_FALSE)
 #define COND_LT		(CR0_LT | COND_CMP_TRUE)

 #define SEEN_DATAREF 0x10000 /* might call external helpers */
 #define SEEN_XREG    0x20000 /* X reg is used */
 #define SEEN_MEM     0x40000 /* SEEN_MEM+(1<<n) = use mem[n] for temporary
 			      * storage */
 #define SEEN_MEM_MSK 0x0ffff

 struct codegen_context {
 	unsigned int seen;
 	unsigned int idx;
 	int pc_ret0; /* bpf index of first RET #0 instruction (if any) */
 };

 #endif

 #endif
	/* bpf_jit.h: BPF JIT compiler for PPC64
	*
	* Copyright 2011 Matt Evans <matt@ozlabs.org>, IBM Corporation
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* as published by the Free Software Foundation; version 2
	* of the License.
	*/
	#ifndef _BPF_JIT_H
	#define _BPF_JIT_H

	#define BPF_PPC_STACK_LOCALS 32
	#define BPF_PPC_STACK_BASIC (48+64)
	#define BPF_PPC_STACK_SAVE (18*8)
	#define BPF_PPC_STACKFRAME (BPF_PPC_STACK_BASIC+BPF_PPC_STACK_LOCALS+ \
	BPF_PPC_STACK_SAVE)
	#define BPF_PPC_SLOWPATH_FRAME (48+64)

	/*
	* Generated code register usage:
	*
	* As normal PPC C ABI (e.g. r1=sp, r2=TOC), with:
	*
	* skb r3 (Entry parameter)
	* A register r4
	* X register r5
	* addr param r6
	* r7-r10 scratch
	* skb->data r14
	* skb headlen r15 (skb->len - skb->data_len)
	* m[0] r16
	* m[...] ...
	* m[15] r31
	*/
	#define r_skb 3
	#define r_ret 3
	#define r_A 4
	#define r_X 5
	#define r_addr 6
	#define r_scratch1 7
	#define r_D 14
	#define r_HL 15
	#define r_M 16

	#ifndef __ASSEMBLY__

	/*
	* Assembly helpers from arch/powerpc/net/bpf_jit.S:
	*/
	#define DECLARE_LOAD_FUNC(func) \
	extern u8 func[], func##_negative_offset[], func##_positive_offset[]

	DECLARE_LOAD_FUNC(sk_load_word);
	DECLARE_LOAD_FUNC(sk_load_half);
	DECLARE_LOAD_FUNC(sk_load_byte);
	DECLARE_LOAD_FUNC(sk_load_byte_msh);

	#define FUNCTION_DESCR_SIZE 24

	/*
	* 16-bit immediate helper macros: HA() is for use with sign-extending instrs
	* (e.g. LD, ADDI). If the bottom 16 bits is "-ve", add another bit into the
	* top half to negate the effect (i.e. 0xffff + 1 = 0x(1)0000).
	*/
	#define IMM_H(i) ((uintptr_t)(i)>>16)
	#define IMM_HA(i) (((uintptr_t)(i)>>16) + \
	(((uintptr_t)(i) & 0x8000) >> 15))
	#define IMM_L(i) ((uintptr_t)(i) & 0xffff)

	#define PLANT_INSTR(d, idx, instr) \
	do { if (d) { (d)[idx] = instr; } idx++; } while (0)
	#define EMIT(instr) PLANT_INSTR(image, ctx->idx, instr)

	#define PPC_NOP() EMIT(PPC_INST_NOP)
	#define PPC_BLR() EMIT(PPC_INST_BLR)
	#define PPC_BLRL() EMIT(PPC_INST_BLRL)
	#define PPC_MTLR(r) EMIT(PPC_INST_MTLR \| __PPC_RT(r))
	#define PPC_ADDI(d, a, i) EMIT(PPC_INST_ADDI \| __PPC_RT(d) \| \
	__PPC_RA(a) \| IMM_L(i))
	#define PPC_MR(d, a) PPC_OR(d, a, a)
	#define PPC_LI(r, i) PPC_ADDI(r, 0, i)
	#define PPC_ADDIS(d, a, i) EMIT(PPC_INST_ADDIS \| \
	__PPC_RS(d) \| __PPC_RA(a) \| IMM_L(i))
	#define PPC_LIS(r, i) PPC_ADDIS(r, 0, i)
	#define PPC_STD(r, base, i) EMIT(PPC_INST_STD \| __PPC_RS(r) \| \
	__PPC_RA(base) \| ((i) & 0xfffc))

	#define PPC_LD(r, base, i) EMIT(PPC_INST_LD \| __PPC_RT(r) \| \
	__PPC_RA(base) \| IMM_L(i))
	#define PPC_LWZ(r, base, i) EMIT(PPC_INST_LWZ \| __PPC_RT(r) \| \
	__PPC_RA(base) \| IMM_L(i))
	#define PPC_LHZ(r, base, i) EMIT(PPC_INST_LHZ \| __PPC_RT(r) \| \
	__PPC_RA(base) \| IMM_L(i))
	/* Convenience helpers for the above with 'far' offsets: */
	#define PPC_LD_OFFS(r, base, i) do { if ((i) < 32768) PPC_LD(r, base, i); \
	else { PPC_ADDIS(r, base, IMM_HA(i)); \
	PPC_LD(r, r, IMM_L(i)); } } while(0)

	#define PPC_LWZ_OFFS(r, base, i) do { if ((i) < 32768) PPC_LWZ(r, base, i); \
	else { PPC_ADDIS(r, base, IMM_HA(i)); \
	PPC_LWZ(r, r, IMM_L(i)); } } while(0)

	#define PPC_LHZ_OFFS(r, base, i) do { if ((i) < 32768) PPC_LHZ(r, base, i); \
	else { PPC_ADDIS(r, base, IMM_HA(i)); \
	PPC_LHZ(r, r, IMM_L(i)); } } while(0)

	#define PPC_CMPWI(a, i) EMIT(PPC_INST_CMPWI \| __PPC_RA(a) \| IMM_L(i))
	#define PPC_CMPDI(a, i) EMIT(PPC_INST_CMPDI \| __PPC_RA(a) \| IMM_L(i))
	#define PPC_CMPLWI(a, i) EMIT(PPC_INST_CMPLWI \| __PPC_RA(a) \| IMM_L(i))
	#define PPC_CMPLW(a, b) EMIT(PPC_INST_CMPLW \| __PPC_RA(a) \| __PPC_RB(b))

	#define PPC_SUB(d, a, b) EMIT(PPC_INST_SUB \| __PPC_RT(d) \| \
	__PPC_RB(a) \| __PPC_RA(b))
	#define PPC_ADD(d, a, b) EMIT(PPC_INST_ADD \| __PPC_RT(d) \| \
	__PPC_RA(a) \| __PPC_RB(b))
	#define PPC_MUL(d, a, b) EMIT(PPC_INST_MULLW \| __PPC_RT(d) \| \
	__PPC_RA(a) \| __PPC_RB(b))
	#define PPC_MULHWU(d, a, b) EMIT(PPC_INST_MULHWU \| __PPC_RT(d) \| \
	__PPC_RA(a) \| __PPC_RB(b))
	#define PPC_MULI(d, a, i) EMIT(PPC_INST_MULLI \| __PPC_RT(d) \| \
	__PPC_RA(a) \| IMM_L(i))
	#define PPC_DIVWU(d, a, b) EMIT(PPC_INST_DIVWU \| __PPC_RT(d) \| \
	__PPC_RA(a) \| __PPC_RB(b))
	#define PPC_AND(d, a, b) EMIT(PPC_INST_AND \| __PPC_RA(d) \| \
	__PPC_RS(a) \| __PPC_RB(b))
	#define PPC_ANDI(d, a, i) EMIT(PPC_INST_ANDI \| __PPC_RA(d) \| \
	__PPC_RS(a) \| IMM_L(i))
	#define PPC_AND_DOT(d, a, b) EMIT(PPC_INST_ANDDOT \| __PPC_RA(d) \| \
	__PPC_RS(a) \| __PPC_RB(b))
	#define PPC_OR(d, a, b) EMIT(PPC_INST_OR \| __PPC_RA(d) \| \
	__PPC_RS(a) \| __PPC_RB(b))
	#define PPC_ORI(d, a, i) EMIT(PPC_INST_ORI \| __PPC_RA(d) \| \
	__PPC_RS(a) \| IMM_L(i))
	#define PPC_ORIS(d, a, i) EMIT(PPC_INST_ORIS \| __PPC_RA(d) \| \
	__PPC_RS(a) \| IMM_L(i))
	#define PPC_SLW(d, a, s) EMIT(PPC_INST_SLW \| __PPC_RA(d) \| \
	__PPC_RS(a) \| __PPC_RB(s))
	#define PPC_SRW(d, a, s) EMIT(PPC_INST_SRW \| __PPC_RA(d) \| \
	__PPC_RS(a) \| __PPC_RB(s))
	/* slwi = rlwinm Rx, Ry, n, 0, 31-n */
	#define PPC_SLWI(d, a, i) EMIT(PPC_INST_RLWINM \| __PPC_RA(d) \| \
	__PPC_RS(a) \| __PPC_SH(i) \| \
	__PPC_MB(0) \| __PPC_ME(31-(i)))
	/* srwi = rlwinm Rx, Ry, 32-n, n, 31 */
	#define PPC_SRWI(d, a, i) EMIT(PPC_INST_RLWINM \| __PPC_RA(d) \| \
	__PPC_RS(a) \| __PPC_SH(32-(i)) \| \
	__PPC_MB(i) \| __PPC_ME(31))
	/* sldi = rldicr Rx, Ry, n, 63-n */
	#define PPC_SLDI(d, a, i) EMIT(PPC_INST_RLDICR \| __PPC_RA(d) \| \
	__PPC_RS(a) \| __PPC_SH(i) \| \
	__PPC_MB(63-(i)) \| (((i) & 0x20) >> 4))
	#define PPC_NEG(d, a) EMIT(PPC_INST_NEG \| __PPC_RT(d) \| __PPC_RA(a))

	/* Long jump; (unconditional 'branch') */
	#define PPC_JMP(dest) EMIT(PPC_INST_BRANCH \| \
	(((dest) - (ctx->idx * 4)) & 0x03fffffc))
	/* "cond" here covers BO:BI fields. */
	#define PPC_BCC_SHORT(cond, dest) EMIT(PPC_INST_BRANCH_COND \| \
	(((cond) & 0x3ff) << 16) \| \
	(((dest) - (ctx->idx * 4)) & \
	0xfffc))
	#define PPC_LI32(d, i) do { PPC_LI(d, IMM_L(i)); \
	if ((u32)(uintptr_t)(i) >= 32768) { \
	PPC_ADDIS(d, d, IMM_HA(i)); \
	} } while(0)
	#define PPC_LI64(d, i) do { \
	if (!((uintptr_t)(i) & 0xffffffff00000000ULL)) \
	PPC_LI32(d, i); \
	else { \
	PPC_LIS(d, ((uintptr_t)(i) >> 48)); \
	if ((uintptr_t)(i) & 0x0000ffff00000000ULL) \
	PPC_ORI(d, d, \
	((uintptr_t)(i) >> 32) & 0xffff); \
	PPC_SLDI(d, d, 32); \
	if ((uintptr_t)(i) & 0x00000000ffff0000ULL) \
	PPC_ORIS(d, d, \
	((uintptr_t)(i) >> 16) & 0xffff); \
	if ((uintptr_t)(i) & 0x000000000000ffffULL) \
	PPC_ORI(d, d, (uintptr_t)(i) & 0xffff); \
	} } while (0);

	static inline bool is_nearbranch(int offset)
	{
	return (offset < 32768) && (offset >= -32768);
	}

	/*
	* The fly in the ointment of code size changing from pass to pass is
	* avoided by padding the short branch case with a NOP. If code size differs
	* with different branch reaches we will have the issue of code moving from
	* one pass to the next and will need a few passes to converge on a stable
	* state.
	*/
	#define PPC_BCC(cond, dest) do { \
	if (is_nearbranch((dest) - (ctx->idx * 4))) { \
	PPC_BCC_SHORT(cond, dest); \
	PPC_NOP(); \
	} else { \
	/* Flip the 'T or F' bit to invert comparison */ \
	PPC_BCC_SHORT(cond ^ COND_CMP_TRUE, (ctx->idx+2)*4); \
	PPC_JMP(dest); \
	} } while(0)

	/* To create a branch condition, select a bit of cr0... */
	#define CR0_LT 0
	#define CR0_GT 1
	#define CR0_EQ 2
	/* ...and modify BO[3] */
	#define COND_CMP_TRUE 0x100
	#define COND_CMP_FALSE 0x000
	/* Together, they make all required comparisons: */
	#define COND_GT (CR0_GT \| COND_CMP_TRUE)
	#define COND_GE (CR0_LT \| COND_CMP_FALSE)
	#define COND_EQ (CR0_EQ \| COND_CMP_TRUE)
	#define COND_NE (CR0_EQ \| COND_CMP_FALSE)
	#define COND_LT (CR0_LT \| COND_CMP_TRUE)

	#define SEEN_DATAREF 0x10000 /* might call external helpers */
	#define SEEN_XREG 0x20000 /* X reg is used */
	#define SEEN_MEM 0x40000 /* SEEN_MEM+(1<<n) = use mem[n] for temporary
	* storage */
	#define SEEN_MEM_MSK 0x0ffff

	struct codegen_context {
	unsigned int seen;
	unsigned int idx;
	int pc_ret0; /* bpf index of first RET #0 instruction (if any) */
	};

	#endif

	#endif