Fix jit compilation bug on wide tables.

The function generated to perform JIT compiled tuple deforming failed
when HeapTupleHeader's t_hoff was bigger than a signed int8. I'd
failed to realize that LLVM's getelementptr would treat an int8 index
argument as signed, rather than unsigned.  That means that a hoff
larger than 127 would result in a negative offset being applied.  Fix
that by widening the index to 32bit.

Add a testcase with a wide table. Don't drop it, as it seems useful to
verify other tools deal properly with wide tables.

Thanks to Justin Pryzby for both reporting a bug and then reducing it
to a reproducible testcase!

Reported-By: Justin Pryzby
Author: Andres Freund
Discussion: https://postgr.es/m/20181115223959.GB10913@telsasoft.com
Backpatch: 11, just as jit compilation was

4 files changed, 30 insertions, 3 deletions

diff --git a/src/backend/jit/llvm/llvmjit_deform.c b/src/backend/jit/llvm/llvmjit_deform.c
index 795f67114e6..e406d392d4e 100644
--- a/src/backend/jit/llvm/llvmjit_deform.c
+++ b/src/backend/jit/llvm/llvmjit_deform.c
@@ -208,10 +208,16 @@ slot_compile_deform(LLVMJitContext *context, TupleDesc desc, int natts)
 							v_infomask2,
 							"maxatt");
 
+	/*
+	 * Need to zext, as getelementptr otherwise treats hoff as a signed 8bit
+	 * integer, which'd yield a negative offset for t_hoff > 127.
+	 */
 	v_hoff =
-		l_load_struct_gep(b, v_tuplep,
-						  FIELDNO_HEAPTUPLEHEADERDATA_HOFF,
-						  "t_hoff");
+		LLVMBuildZExt(b,
+					  l_load_struct_gep(b, v_tuplep,
+										FIELDNO_HEAPTUPLEHEADERDATA_HOFF,
+										""),
+					  LLVMInt32Type(), "t_hoff");
 
 	v_tupdata_base =
 		LLVMBuildGEP(b,
diff --git a/src/test/regress/expected/create_table.out b/src/test/regress/expected/create_table.out
index e156e800c22..8cd148601d2 100644
--- a/src/test/regress/expected/create_table.out
+++ b/src/test/regress/expected/create_table.out
@@ -263,6 +263,16 @@ ERROR:  relation "as_select1" already exists
 CREATE TABLE IF NOT EXISTS as_select1 AS SELECT * FROM pg_class WHERE relkind = 'r';
 NOTICE:  relation "as_select1" already exists, skipping
 DROP TABLE as_select1;
+-- create an extra wide table to test for issues related to that
+-- (temporarily hide query, to avoid the long CREATE TABLE stmt)
+\set ECHO none
+INSERT INTO extra_wide_table(firstc, lastc) VALUES('first col', 'last col');
+SELECT firstc, lastc FROM extra_wide_table;
+  firstc   |  lastc   
+-----------+----------
+ first col | last col
+(1 row)
+
 -- check that the oid column is added before the primary key is checked
 CREATE TABLE oid_pk (f1 INT, PRIMARY KEY(oid)) WITH OIDS;
 DROP TABLE oid_pk;
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index 9c7a60c092d..66957706a00 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -44,6 +44,7 @@ dupindexcols|t
 e_star|f
 emp|f
 equipment_r|f
+extra_wide_table|f
 f_star|f
 fast_emp4000|t
 float4_tbl|f
diff --git a/src/test/regress/sql/create_table.sql b/src/test/regress/sql/create_table.sql
index 2af4455ecf8..df8b66fac4d 100644
--- a/src/test/regress/sql/create_table.sql
+++ b/src/test/regress/sql/create_table.sql
@@ -278,6 +278,16 @@ CREATE TABLE as_select1 AS SELECT * FROM pg_class WHERE relkind = 'r';
 CREATE TABLE IF NOT EXISTS as_select1 AS SELECT * FROM pg_class WHERE relkind = 'r';
 DROP TABLE as_select1;
 
+-- create an extra wide table to test for issues related to that
+-- (temporarily hide query, to avoid the long CREATE TABLE stmt)
+\set ECHO none
+SELECT 'CREATE TABLE extra_wide_table(firstc text, '|| array_to_string(array_agg('c'||i||' bool'),',')||', lastc text);'
+FROM generate_series(1, 1100) g(i)
+\gexec
+\set ECHO all
+INSERT INTO extra_wide_table(firstc, lastc) VALUES('first col', 'last col');
+SELECT firstc, lastc FROM extra_wide_table;
+
 -- check that the oid column is added before the primary key is checked
 CREATE TABLE oid_pk (f1 INT, PRIMARY KEY(oid)) WITH OIDS;
 DROP TABLE oid_pk;