jit: Fix type used for Datum values in LLVM IR.

Commit 2a600a9 made Datum 8 bytes wide everywhere.  It was no longer
appropriate to use TypeSizeT on 32 bit systems, and JIT compilation
would fail with various type check errors.  Introduce a separate
LLVMTypeRef with the name TypeDatum.  TypeSizeT is still used in some
places for actual size_t values.

Reported-by: Dmitry Mityugov <d.mityugov@postgrespro.ru>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Tested-by: Dmitry Mityugov <d.mityugov@postgrespro.ru>
Discussion: https://postgr.es/m/0a9f0be59171c2e8f1b3bc10f4fcf267%40postgrespro.ru

Author: macdice

src/backend/jit/llvm/llvmjit.c

@@ -54,6 +54,7 @@ typedef struct LLVMJitHandle
 
 /* types & functions commonly needed for JITing */
 LLVMTypeRef TypeSizeT;
+LLVMTypeRef TypeDatum;
 LLVMTypeRef TypeParamBool;
 LLVMTypeRef TypeStorageBool;
 LLVMTypeRef TypePGFunction;
@@ -1011,6 +1012,7 @@ llvm_create_types(void)
 	LLVMDisposeMemoryBuffer(buf);
 
 	TypeSizeT = llvm_pg_var_type("TypeSizeT");
+	TypeDatum = llvm_pg_var_type("TypeDatum");
 	TypeParamBool = load_return_type(llvm_types_module, "FunctionReturningBool");
 	TypeStorageBool = llvm_pg_var_type("TypeStorageBool");
 	TypePGFunction = llvm_pg_var_type("TypePGFunction");

src/backend/jit/llvm/llvmjit_deform.c

@@ -479,8 +479,8 @@ slot_compile_deform(LLVMJitContext *context, TupleDesc desc,
 						   l_gep(b, LLVMInt8TypeInContext(lc), v_tts_nulls, &l_attno, 1, ""));
 			/* store zero datum */
 			LLVMBuildStore(b,
-						   l_sizet_const(0),
-						   l_gep(b, TypeSizeT, v_tts_values, &l_attno, 1, ""));
+						   l_datum_const(0),
+						   l_gep(b, TypeDatum, v_tts_values, &l_attno, 1, ""));
 
 			LLVMBuildBr(b, b_next);
 			attguaranteedalign = false;
@@ -644,7 +644,7 @@ slot_compile_deform(LLVMJitContext *context, TupleDesc desc,
 		}
 
 		/* compute address to store value at */
-		v_resultp = l_gep(b, TypeSizeT, v_tts_values, &l_attno, 1, "");
+		v_resultp = l_gep(b, TypeDatum, v_tts_values, &l_attno, 1, "");
 
 		/* store null-byte (false) */
 		LLVMBuildStore(b, l_int8_const(lc, 0),
@@ -663,7 +663,7 @@ slot_compile_deform(LLVMJitContext *context, TupleDesc desc,
 			v_tmp_loaddata =
 				LLVMBuildPointerCast(b, v_attdatap, vartypep, "");
 			v_tmp_loaddata = l_load(b, vartype, v_tmp_loaddata, "attr_byval");
-			v_tmp_loaddata = LLVMBuildZExt(b, v_tmp_loaddata, TypeSizeT, "");
+			v_tmp_loaddata = LLVMBuildZExt(b, v_tmp_loaddata, TypeDatum, "");
 
 			LLVMBuildStore(b, v_tmp_loaddata, v_resultp);
 		}
@@ -675,7 +675,7 @@ slot_compile_deform(LLVMJitContext *context, TupleDesc desc,
 			v_tmp_loaddata =
 				LLVMBuildPtrToInt(b,
 								  v_attdatap,
-								  TypeSizeT,
+								  TypeDatum,
 								  "attr_ptr");
 			LLVMBuildStore(b, v_tmp_loaddata, v_resultp);
 		}