[Transforms] Do not drop !preserve.access.index metadata
Currently, when a GVN or CSE optimization happens,
the llvm.preserve.access.index metadata is dropped.
This caused a problem for BPF AbstructMemberOffset phase
as it relies on the metadata (debuginfo types).
This patch added proper hooks in lib/Transforms to
preserve !preserve.access.index metadata. A test
case is added to ensure metadata is preserved under CSE.
Differential Revision: https://reviews.llvm.org/D65700
llvm-svn: 367769
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 63015e6..33dbbf9 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1313,7 +1313,8 @@
LLVMContext::MD_dereferenceable,
LLVMContext::MD_dereferenceable_or_null,
LLVMContext::MD_mem_parallel_loop_access,
- LLVMContext::MD_access_group};
+ LLVMContext::MD_access_group,
+ LLVMContext::MD_preserve_access_index};
combineMetadata(I1, I2, KnownIDs, true);
// I1 and I2 are being combined into a single instruction. Its debug