jit: Remove redundancies in expression evaluation code generation.

This merges the code emission for a number of opcodes by handling the
behavioural difference more locally. This reduces code, and also
improves the generated code a bit in some cases, by removing redundant
constants.

Author: Andres Freund
Discussion: https://postgr.es/m/20191023163849.sosqbfs5yenocez3@alap3.anarazel.de

src/backend/jit/llvm/llvmjit_expr.c

@@ -471,6 +471,7 @@ llvm_compile_expr(ExprState *state)
 				}
 
 			case EEOP_ASSIGN_TMP:
+			case EEOP_ASSIGN_TMP_MAKE_RO:
 				{
 					LLVMValueRef v_value,
 								v_isnull;
@@ -490,43 +491,18 @@ llvm_compile_expr(ExprState *state)
 					v_risnullp =
 						LLVMBuildGEP(b, v_resultnulls, &v_resultnum, 1, "");
 
-					/* and store */
-					LLVMBuildStore(b, v_value, v_rvaluep);
+					/* store nullness */
 					LLVMBuildStore(b, v_isnull, v_risnullp);
 
-					LLVMBuildBr(b, opblocks[opno + 1]);
-					break;
-				}
-
-			case EEOP_ASSIGN_TMP_MAKE_RO:
+					/* make value readonly if necessary */
+					if (opcode == EEOP_ASSIGN_TMP_MAKE_RO)
 					{
 						LLVMBasicBlockRef b_notnull;
 						LLVMValueRef v_params[1];
-					LLVMValueRef v_ret;
-					LLVMValueRef v_value,
-								v_isnull;
-					LLVMValueRef v_rvaluep,
-								v_risnullp;
-					LLVMValueRef v_resultnum;
-					size_t		resultnum = op->d.assign_tmp.resultnum;
 
 						b_notnull = l_bb_before_v(opblocks[opno + 1],
 												  "op.%d.assign_tmp.notnull", opno);
 
-					/* load data */
-					v_value = LLVMBuildLoad(b, v_tmpvaluep, "");
-					v_isnull = LLVMBuildLoad(b, v_tmpisnullp, "");
-
-					/* compute addresses of targets */
-					v_resultnum = l_int32_const(resultnum);
-					v_rvaluep = LLVMBuildGEP(b, v_resultvalues,
-											 &v_resultnum, 1, "");
-					v_risnullp = LLVMBuildGEP(b, v_resultnulls,
-											  &v_resultnum, 1, "");
-
-					/* store nullness */
-					LLVMBuildStore(b, v_isnull, v_risnullp);
-
 						/* check if value is NULL */
 						LLVMBuildCondBr(b,
 										LLVMBuildICmp(b, LLVMIntEQ, v_isnull,
@@ -536,13 +512,19 @@ llvm_compile_expr(ExprState *state)
 						/* if value is not null, convert to RO datum */
 						LLVMPositionBuilderAtEnd(b, b_notnull);
 						v_params[0] = v_value;
-					v_ret =
+						v_value =
 							LLVMBuildCall(b,
 										  llvm_get_decl(mod, FuncMakeExpandedObjectReadOnlyInternal),
 										  v_params, lengthof(v_params), "");
 
-					/* store value */
-					LLVMBuildStore(b, v_ret, v_rvaluep);
+						/*
+						 * Falling out of the if () with builder in b_notnull,
+						 * which is fine - the null is already stored above.
+						 */
+					}
+
+					/* and finally store result */
+					LLVMBuildStore(b, v_value, v_rvaluep);
 
 					LLVMBuildBr(b, opblocks[opno + 1]);
 					break;
@@ -563,12 +545,18 @@ llvm_compile_expr(ExprState *state)
 					break;
 				}
 
+			case EEOP_FUNCEXPR:
 			case EEOP_FUNCEXPR_STRICT:
 				{
 					FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
+					LLVMValueRef v_fcinfo_isnull;
+					LLVMValueRef v_retval;
+
+					if (opcode == EEOP_FUNCEXPR_STRICT)
+					{
 						LLVMBasicBlockRef b_nonull;
-					LLVMValueRef v_fcinfo;
 						LLVMBasicBlockRef *b_checkargnulls;
+						LLVMValueRef v_fcinfo;
 
 						/*
 						 * Block for the actual function call, if args are
@@ -595,7 +583,8 @@ llvm_compile_expr(ExprState *state)
 							palloc(sizeof(LLVMBasicBlockRef *) * op->d.func.nargs);
 						for (int argno = 0; argno < op->d.func.nargs; argno++)
 							b_checkargnulls[argno] =
-							l_bb_before_v(b_nonull, "b.%d.isnull.%d", opno, argno);
+								l_bb_before_v(b_nonull, "b.%d.isnull.%d", opno,
+											  argno);
 
 						/* jump to check of first argument */
 						LLVMBuildBr(b, b_checkargnulls[0]);
@@ -608,7 +597,10 @@ llvm_compile_expr(ExprState *state)
 
 							LLVMPositionBuilderAtEnd(b, b_checkargnulls[argno]);
 
-						/* compute block to jump to if argument is not null */
+							/*
+							 * Compute block to jump to if argument is not
+							 * null.
+							 */
 							if (argno + 1 == op->d.func.nargs)
 								b_argnotnull = b_nonull;
 							else
@@ -627,13 +619,6 @@ llvm_compile_expr(ExprState *state)
 
 						LLVMPositionBuilderAtEnd(b, b_nonull);
 					}
-				/* FALLTHROUGH */
-
-			case EEOP_FUNCEXPR:
-				{
-					FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
-					LLVMValueRef v_fcinfo_isnull;
-					LLVMValueRef v_retval;
 
 					v_retval = BuildV1Call(context, b, mod, fcinfo,
 										   &v_fcinfo_isnull);
@@ -657,24 +642,14 @@ llvm_compile_expr(ExprState *state)
 				LLVMBuildBr(b, opblocks[opno + 1]);
 				break;
 
-			case EEOP_BOOL_AND_STEP_FIRST:
-				{
-					LLVMValueRef v_boolanynullp;
-
-					v_boolanynullp = l_ptr_const(op->d.boolexpr.anynull,
-												 l_ptr(TypeStorageBool));
-					LLVMBuildStore(b, l_sbool_const(0), v_boolanynullp);
-
-				}
-				/* FALLTHROUGH */
-
 				/*
 				 * Treat them the same for now, optimizer can remove
 				 * redundancy. Could be worthwhile to optimize during emission
 				 * though.
 				 */
-			case EEOP_BOOL_AND_STEP_LAST:
+			case EEOP_BOOL_AND_STEP_FIRST:
 			case EEOP_BOOL_AND_STEP:
+			case EEOP_BOOL_AND_STEP_LAST:
 				{
 					LLVMValueRef v_boolvalue;
 					LLVMValueRef v_boolnull;
@@ -700,6 +675,9 @@ llvm_compile_expr(ExprState *state)
 					v_boolanynullp = l_ptr_const(op->d.boolexpr.anynull,
 												 l_ptr(TypeStorageBool));
 
+					if (opcode == EEOP_BOOL_AND_STEP_FIRST)
+						LLVMBuildStore(b, l_sbool_const(0), v_boolanynullp);
+
 					v_boolnull = LLVMBuildLoad(b, v_resnullp, "");
 					v_boolvalue = LLVMBuildLoad(b, v_resvaluep, "");
 
@@ -759,23 +737,15 @@ llvm_compile_expr(ExprState *state)
 					LLVMBuildBr(b, opblocks[opno + 1]);
 					break;
 				}
-			case EEOP_BOOL_OR_STEP_FIRST:
-				{
-					LLVMValueRef v_boolanynullp;
-
-					v_boolanynullp = l_ptr_const(op->d.boolexpr.anynull,
-												 l_ptr(TypeStorageBool));
-					LLVMBuildStore(b, l_sbool_const(0), v_boolanynullp);
-				}
-				/* FALLTHROUGH */
 
 				/*
 				 * Treat them the same for now, optimizer can remove
 				 * redundancy. Could be worthwhile to optimize during emission
 				 * though.
 				 */
-			case EEOP_BOOL_OR_STEP_LAST:
+			case EEOP_BOOL_OR_STEP_FIRST:
 			case EEOP_BOOL_OR_STEP:
+			case EEOP_BOOL_OR_STEP_LAST:
 				{
 					LLVMValueRef v_boolvalue;
 					LLVMValueRef v_boolnull;
@@ -802,6 +772,8 @@ llvm_compile_expr(ExprState *state)
 					v_boolanynullp = l_ptr_const(op->d.boolexpr.anynull,
 												 l_ptr(TypeStorageBool));
 
+					if (opcode == EEOP_BOOL_OR_STEP_FIRST)
+						LLVMBuildStore(b, l_sbool_const(0), v_boolanynullp);
 					v_boolnull = LLVMBuildLoad(b, v_resnullp, "");
 					v_boolvalue = LLVMBuildLoad(b, v_resvaluep, "");
 
@@ -1958,8 +1930,18 @@ llvm_compile_expr(ExprState *state)
 				break;
 
 			case EEOP_AGG_STRICT_DESERIALIZE:
+			case EEOP_AGG_DESERIALIZE:
 				{
+					AggState   *aggstate;
 					FunctionCallInfo fcinfo = op->d.agg_deserialize.fcinfo_data;
+
+					LLVMValueRef v_retval;
+					LLVMValueRef v_fcinfo_isnull;
+					LLVMValueRef v_tmpcontext;
+					LLVMValueRef v_oldcontext;
+
+					if (opcode == EEOP_AGG_STRICT_DESERIALIZE)
+					{
 						LLVMValueRef v_fcinfo;
 						LLVMValueRef v_argnull0;
 						LLVMBasicBlockRef b_deserialize;
@@ -1981,17 +1963,6 @@ llvm_compile_expr(ExprState *state)
 										b_deserialize);
 						LLVMPositionBuilderAtEnd(b, b_deserialize);
 					}
-				/* FALLTHROUGH */
-
-			case EEOP_AGG_DESERIALIZE:
-				{
-					AggState   *aggstate;
-					FunctionCallInfo fcinfo;
-
-					LLVMValueRef v_retval;
-					LLVMValueRef v_fcinfo_isnull;
-					LLVMValueRef v_tmpcontext;
-					LLVMValueRef v_oldcontext;
 
 					aggstate = castNode(AggState, state->parent);
 					fcinfo = op->d.agg_deserialize.fcinfo_data;