Add FIELDNO_* macro designating offset into structs required for JIT.

For any interesting JIT target, fields inside structs need to be
accessed. b96d550e contains infrastructure for syncing the definition
of types between postgres C code and runtime code generation with
LLVM. But that doesn't sync the number or names of fields inside
structs, just the types (including padding etc).

One option would be to hardcode the offset numbers in the JIT code,
but that'd be hard to keep in sync. Instead add macros indicating the
field offset to the fields that need to be accessed. Not pretty, but
manageable.

Author: Andres Freund
Discussion: https://postgr.es/m/20170901064131.tazjxwus3k2w3ybh@alap3.anarazel.de

src/include/access/htup.h

@@ -64,6 +64,7 @@ typedef struct HeapTupleData
 	uint32		t_len;			/* length of *t_data */
 	ItemPointerData t_self;		/* SelfItemPointer */
 	Oid			t_tableOid;		/* table the tuple came from */
+#define FIELDNO_HEAPTUPLEDATA_DATA 3
 	HeapTupleHeader t_data;		/* -> tuple header and data */
 } HeapTupleData;
 

src/include/access/htup_details.h

@@ -157,14 +157,18 @@ struct HeapTupleHeaderData
 
 	/* Fields below here must match MinimalTupleData! */
 
+#define FIELDNO_HEAPTUPLEHEADERDATA_INFOMASK2 2
 	uint16		t_infomask2;	/* number of attributes + various flags */
 
+#define FIELDNO_HEAPTUPLEHEADERDATA_INFOMASK 3
 	uint16		t_infomask;		/* various flag bits, see below */
 
+#define FIELDNO_HEAPTUPLEHEADERDATA_HOFF 4
 	uint8		t_hoff;			/* sizeof header incl. bitmap, padding */
 
 	/* ^ - 23 bytes - ^ */
 
+#define FIELDNO_HEAPTUPLEHEADERDATA_BITS 5
 	bits8		t_bits[FLEXIBLE_ARRAY_MEMBER];	/* bitmap of NULLs */
 
 	/* MORE DATA FOLLOWS AT END OF STRUCT */

src/include/executor/nodeAgg.h

@@ -240,9 +240,12 @@ typedef struct AggStatePerAggData
  */
 typedef struct AggStatePerGroupData
 {
+#define FIELDNO_AGGSTATEPERGROUPDATA_TRANSVALUE 0
 	Datum		transValue;		/* current transition value */
+#define FIELDNO_AGGSTATEPERGROUPDATA_TRANSVALUEISNULL 1
 	bool		transValueIsNull;
 
+#define FIELDNO_AGGSTATEPERGROUPDATA_NOTRANSVALUE 2
 	bool		noTransValue;	/* true if transValue not set yet */
 
 	/*

src/include/executor/tuptable.h

@@ -116,16 +116,23 @@ typedef struct TupleTableSlot
 	bool		tts_isempty;	/* true = slot is empty */
 	bool		tts_shouldFree; /* should pfree tts_tuple? */
 	bool		tts_shouldFreeMin;	/* should pfree tts_mintuple? */
+#define FIELDNO_TUPLETABLESLOT_SLOW 4
 	bool		tts_slow;		/* saved state for slot_deform_tuple */
+#define FIELDNO_TUPLETABLESLOT_TUPLE 5
 	HeapTuple	tts_tuple;		/* physical tuple, or NULL if virtual */
+#define FIELDNO_TUPLETABLESLOT_TUPLEDESCRIPTOR 6
 	TupleDesc	tts_tupleDescriptor;	/* slot's tuple descriptor */
 	MemoryContext tts_mcxt;		/* slot itself is in this context */
 	Buffer		tts_buffer;		/* tuple's buffer, or InvalidBuffer */
+#define FIELDNO_TUPLETABLESLOT_NVALID 9
 	int			tts_nvalid;		/* # of valid values in tts_values */
+#define FIELDNO_TUPLETABLESLOT_VALUES 10
 	Datum	   *tts_values;		/* current per-attribute values */
+#define FIELDNO_TUPLETABLESLOT_ISNULL 11
 	bool	   *tts_isnull;		/* current per-attribute isnull flags */
 	MinimalTuple tts_mintuple;	/* minimal tuple, or NULL if none */
 	HeapTupleData tts_minhdr;	/* workspace for minimal-tuple-only case */
+#define FIELDNO_TUPLETABLESLOT_OFF 14
 	uint32		tts_off;		/* saved state for slot_deform_tuple */
 	bool		tts_fixedTupleDescriptor; /* descriptor can't be changed */
 } TupleTableSlot;

src/include/fmgr.h

@@ -80,9 +80,12 @@ typedef struct FunctionCallInfoData
 	fmNodePtr	context;		/* pass info about context of call */
 	fmNodePtr	resultinfo;		/* pass or return extra info about result */
 	Oid			fncollation;	/* collation for function to use */
+#define FIELDNO_FUNCTIONCALLINFODATA_ISNULL 4
 	bool		isnull;			/* function must set true if result is NULL */
 	short		nargs;			/* # arguments actually passed */
+#define FIELDNO_FUNCTIONCALLINFODATA_ARG 6
 	Datum		arg[FUNC_MAX_ARGS]; /* Arguments passed to function */
+#define FIELDNO_FUNCTIONCALLINFODATA_ARGNULL 7
 	bool		argnull[FUNC_MAX_ARGS]; /* T if arg[i] is actually NULL */
 } FunctionCallInfoData;
 

src/include/nodes/execnodes.h

@@ -64,12 +64,15 @@ typedef struct ExprState
 	 * Storage for result value of a scalar expression, or for individual
 	 * column results within expressions built by ExecBuildProjectionInfo().
 	 */
+#define FIELDNO_EXPRSTATE_RESNULL 2
 	bool		resnull;
+#define FIELDNO_EXPRSTATE_RESVALUE 3
 	Datum		resvalue;
 
 	/*
 	 * If projecting a tuple result, this slot holds the result; else NULL.
 	 */
+#define FIELDNO_EXPRSTATE_RESULTSLOT 4
 	TupleTableSlot *resultslot;
 
 	/*
@@ -208,8 +211,11 @@ typedef struct ExprContext
 	NodeTag		type;
 
 	/* Tuples that Var nodes in expression may refer to */
+#define FIELDNO_EXPRCONTEXT_SCANTUPLE 1
 	TupleTableSlot *ecxt_scantuple;
+#define FIELDNO_EXPRCONTEXT_INNERTUPLE 2
 	TupleTableSlot *ecxt_innertuple;
+#define FIELDNO_EXPRCONTEXT_OUTERTUPLE 3
 	TupleTableSlot *ecxt_outertuple;
 
 	/* Memory contexts for expression evaluation --- see notes above */
@@ -224,15 +230,21 @@ typedef struct ExprContext
 	 * Values to substitute for Aggref nodes in the expressions of an Agg
 	 * node, or for WindowFunc nodes within a WindowAgg node.
 	 */
+#define FIELDNO_EXPRCONTEXT_AGGVALUES 8
 	Datum	   *ecxt_aggvalues; /* precomputed values for aggs/windowfuncs */
+#define FIELDNO_EXPRCONTEXT_AGGNULLS 9
 	bool	   *ecxt_aggnulls;	/* null flags for aggs/windowfuncs */
 
 	/* Value to substitute for CaseTestExpr nodes in expression */
+#define FIELDNO_EXPRCONTEXT_CASEDATUM 10
 	Datum		caseValue_datum;
+#define FIELDNO_EXPRCONTEXT_CASENULL 11
 	bool		caseValue_isNull;
 
 	/* Value to substitute for CoerceToDomainValue nodes in expression */
+#define FIELDNO_EXPRCONTEXT_DOMAINDATUM 12
 	Datum		domainValue_datum;
+#define FIELDNO_EXPRCONTEXT_DOMAINNULL 13
 	bool		domainValue_isNull;
 
 	/* Link to containing EState (NULL if a standalone ExprContext) */
@@ -1847,12 +1859,15 @@ typedef struct AggState
 	ExprContext *hashcontext;	/* econtexts for long-lived data (hashtable) */
 	ExprContext **aggcontexts;	/* econtexts for long-lived data (per GS) */
 	ExprContext *tmpcontext;	/* econtext for input expressions */
+#define FIELDNO_AGGSTATE_CURAGGCONTEXT 14
 	ExprContext *curaggcontext; /* currently active aggcontext */
 	AggStatePerAgg curperagg;	/* currently active aggregate, if any */
+#define FIELDNO_AGGSTATE_CURPERTRANS 16
 	AggStatePerTrans curpertrans;	/* currently active trans state, if any */
 	bool		input_done;		/* indicates end of input */
 	bool		agg_done;		/* indicates completion of Agg scan */
 	int			projected_set;	/* The last projected grouping set */
+#define FIELDNO_AGGSTATE_CURRENT_SET 20
 	int			current_set;	/* The current grouping set being evaluated */
 	Bitmapset  *grouped_cols;	/* grouped cols in current projection */
 	List	   *all_grouped_cols;	/* list of all grouped cols in DESC order */
@@ -1874,6 +1889,7 @@ typedef struct AggState
 										 * per-group pointers */
 
 	/* support for evaluation of agg input expressions: */
+#define FIELDNO_AGGSTATE_ALL_PERGROUPS 34
 	AggStatePerGroup *all_pergroups;	/* array of first ->pergroups, than
 										 * ->hash_pergroup */
 	ProjectionInfo *combinedproj;	/* projection machinery */