From: Jakub Jirutka <jakub@jirutka.cz>
Date: Sat, 18 Dec 2021 23:35:00 +0100
Subject: [PATCH] jit: Workaround datalayout mismatch on s390x

LLVM's s390x target uses a different datalayout for z13 and newer processors.
If llvmjit_types.bc is compiled to target a processor older than z13, and
then the JIT runs on a z13 or newer processor, then there will be a mismatch
in datalayouts between llvmjit_types.bc and the JIT engine.  This mismatch
causes the JIT to fail at runtime.

This patch is inspired by https://src.fedoraproject.org/rpms/postgresql/pull-request/29.
We couldn't use https://src.fedoraproject.org/rpms/postgresql/blob/f35/f/postgresql-datalayout-mismatch-on-s390.patch
because it doesn't compile on PostgreSQL 12 (llvm_types_module is undeclared).

diff --git a/src/backend/jit/llvm/llvmjit.c b/src/backend/jit/llvm/llvmjit.c
--- a/src/backend/jit/llvm/llvmjit.c
+++ b/src/backend/jit/llvm/llvmjit.c
@@ -780,10 +780,12 @@
 	 * latter is needed because some CPU architectures default to enabling
 	 * features not all CPUs have (weird, huh).
 	 */
+#if !defined(__s390__) && !defined(__s390x__)  // XXX: quick workaround for s390x
 	cpu = LLVMGetHostCPUName();
 	features = LLVMGetHostCPUFeatures();
 	elog(DEBUG2, "LLVMJIT detected CPU \"%s\", with features \"%s\"",
 		 cpu, features);
+#endif
 
 	opt0_tm =
 		LLVMCreateTargetMachine(llvm_targetref, llvm_triple, cpu, features,