Semantic patch for pg_cmp_* functions

In commit 3b42bdb and 6b80394 overflow-safe comparison functions where
introduced, but they are not widely used. This semantic patch identifies some
of the more common cases and replaces them with calls to the corresponding
pg_cmp_* function.

Author: mkindahl

cocci/use_pg_cmp.cocci

@@ -0,0 +1,125 @@
+// Find cases where we can use the new pg_cmp_* functions.
+//
+// Copyright 2025 Mats Kindahl, Timescale.
+//
+// Options: --no-includes --include-headers
+
+virtual report
+virtual context
+virtual patch
+
+@initialize:python@
+@@
+
+import re
+
+TYPMAP = {
+       'BlockNumber': 'pg_cmp_u32',
+       'ForkNumber': 'pg_cmp_s32',
+       'OffsetNumber': 'pg_cmp_s16',
+       'int': 'pg_cmp_s32',
+       'int16': 'pg_cmp_s16',
+       'int32': 'pg_cmp_s32',
+       'uint16': 'pg_cmp_u16',
+       'uint32': 'pg_cmp_u32',
+       'unsigned int': 'pg_cmp_u32',
+}
+
+def is_valid(expr):
+    return not re.search(r'DatumGet[A-Za-z]+', expr)
+
+@r1e depends on context || report expression@
+type TypeName : script:python() { TypeName in TYPMAP };
+position pos;
+TypeName lhs : script:python() { is_valid(lhs) };
+TypeName rhs : script:python() { is_valid(rhs) };
+@@
+* lhs@pos < rhs ? -1 : lhs > rhs ? 1 : 0
+
+@script:python depends on report@
+lhs << r1e.lhs;
+rhs << r1e.rhs;
+pos << r1e.pos;
+@@
+coccilib.report.print_report(pos[0], f"conditional checks between '{lhs}' and '{rhs}' can be replaced with a PostgreSQL comparison function")
+
+@r1 depends on context || report@
+type TypeName : script:python() { TypeName in TYPMAP };
+position pos;
+TypeName lhs : script:python() { is_valid(lhs) };
+TypeName rhs : script:python() { is_valid(rhs) };
+@@
+(
+* if@pos (lhs < rhs) return -1; else if (lhs > rhs) return 1; return 0;
+|
+* if@pos (lhs < rhs) return -1; else if (lhs > rhs) return 1; else return 0;
+|
+* if@pos (lhs < rhs) return -1; if (lhs > rhs) return 1; return 0;
+|
+* if@pos (lhs > rhs) return 1; if (lhs < rhs) return -1; return 0;
+|
+* if@pos (lhs == rhs) return 0; if (lhs > rhs) return 1; return -1;
+|
+* if@pos (lhs == rhs) return 0; return lhs > rhs ? 1 : -1;
+|
+* if@pos (lhs == rhs) return 0; return lhs < rhs ? -1 : 1;
+)
+
+@script:python depends on report@
+lhs << r1.lhs;
+rhs << r1.rhs;
+pos << r1.pos;
+@@
+coccilib.report.print_report(pos[0], f"conditional checks between '{lhs}' and '{rhs}' can be replaced with a PostgreSQL comparison function")
+
+@expr_repl depends on patch expression@
+type TypeName : script:python() { TypeName in TYPMAP };
+fresh identifier cmp = script:python(TypeName) { TYPMAP[TypeName] };
+TypeName lhs : script:python() { is_valid(lhs) };
+TypeName rhs : script:python() { is_valid(rhs) };
+@@
+- lhs < rhs ? -1 : lhs > rhs ? 1 : 0
++ cmp(lhs,rhs)
+
+@stmt_repl depends on patch@
+type TypeName : script:python() { TypeName in TYPMAP };
+fresh identifier cmp = script:python(TypeName) { TYPMAP[TypeName] };
+TypeName lhs : script:python() { is_valid(lhs) };
+TypeName rhs : script:python() { is_valid(rhs) };
+@@
+(
+- if (lhs < rhs) return -1; if (lhs > rhs) return 1; return 0;
++ return cmp(lhs,rhs);
+|
+- if (lhs < rhs) return -1; else if (lhs > rhs) return 1; return 0;
++ return cmp(lhs,rhs);
+|
+- if (lhs < rhs) return -1; else if (lhs > rhs) return 1; else return 0;
++ return cmp(lhs,rhs);
+|
+- if (lhs > rhs) return 1; if (lhs < rhs) return -1; return 0;
++ return cmp(lhs,rhs);
+|
+- if (lhs > rhs) return 1; else if (lhs < rhs) return -1; return 0;
++ return cmp(lhs,rhs);
+|
+- if (lhs == rhs) return 0; if (lhs > rhs) return 1; return -1;
++ return cmp(lhs,rhs);
+|
+- if (lhs == rhs) return 0; return lhs > rhs ? 1 : -1;
++ return cmp(lhs,rhs);
+|
+- if (lhs == rhs) return 0; return lhs < rhs ? -1 : 1;
++ return cmp(lhs,rhs);
+)
+
+// Add an include if there were none and we had to do some
+// replacements
+@has_include depends on patch@
+@@
+  #include "common/int.h"
+
+@depends on patch && !has_include && (stmt_repl || expr_repl)@
+@@
+  #include ...
++ #include "common/int.h"