[llvm] 10b1a61 - Revert "[jitlink][ELF] Add zero-fill blocks for symbols in section SHN_COMMON"

[Stefan Gränitz via llvm-commits]

Author: Stefan Gränitz
Date: 2020-10-24T15:43:06+02:00
New Revision: 10b1a61bafba39fd7400a814a7272f41222ad579

URL: https://github.com/llvm/llvm-project/commit/10b1a61bafba39fd7400a814a7272f41222ad579
DIFF: https://github.com/llvm/llvm-project/commit/10b1a61bafba39fd7400a814a7272f41222ad579.diff

LOG: Revert "[jitlink][ELF] Add zero-fill blocks for symbols in section SHN_COMMON"

This reverts commit e9955b0843cc1e5876430f3f051494d4197419f3. Cannot reproduce the buildbot failures yet. Reverting in the meantime.

Added: 
    

Modified: 
    llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp

Removed: 
    llvm/test/ExecutionEngine/JITLink/X86/ELF_x86-64_common.s


################################################################################
diff  --git a/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp b/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
index 4f48378186f0..821a7b3cc44e 100644
--- a/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
@@ -510,17 +510,6 @@ class ELFLinkGraphBuilder_x86_64 {
         // I am not sure on If this is going to hold as an invariant. Revisit.
         if (!Name)
           return Name.takeError();
-
-        if (SymRef.isCommon()) {
-          // Symbols in SHN_COMMON refer to uninitialized data. The st_value
-          // field holds alignment constraints.
-          Symbol &S =
-              G->addCommonSymbol(*Name, Scope::Default, getCommonSection(), 0,
-                                 SymRef.st_size, SymRef.getValue(), false);
-          JITSymbolTable[SymbolIndex] = &S;
-          continue;
-        }
-
         // TODO: weak and hidden
         if (SymRef.isExternal())
           bindings = {Linkage::Strong, Scope::Default};
@@ -561,12 +550,18 @@ class ELFLinkGraphBuilder_x86_64 {
           JITSymbolTable[SymbolIndex] = &S;
         }
 
+        //  }
         // TODO: The following has to be implmented.
         // leaving commented out to save time for future patchs
         /*
           G->addAbsoluteSymbol(*Name, SymRef.getValue(), SymRef.st_size,
           Linkage::Strong, Scope::Default, false);
-        */
+
+          if(SymRef.isCommon()) {
+            G->addCommonSymbol(*Name, Scope::Default, getCommonSection(), 0, 0,
+          SymRef.getValue(), false);
+          }
+  */
       }
     }
     return Error::success();

diff  --git a/llvm/test/ExecutionEngine/JITLink/X86/ELF_x86-64_common.s b/llvm/test/ExecutionEngine/JITLink/X86/ELF_x86-64_common.s
deleted file mode 100644
index 865b3f8aa49a..000000000000
--- a/llvm/test/ExecutionEngine/JITLink/X86/ELF_x86-64_common.s
+++ /dev/null
@@ -1,25 +0,0 @@
-# RUN: rm -rf %t && mkdir -p %t
-# RUN: llvm-mc -triple=x86_64-unknown-linux -position-independent -filetype=obj -o %t/elf_common.o %s
-# RUN: llvm-jitlink -entry=load_common -noexec -check %s %t/elf_common.o
-
-        .text
-        .file   "elf_common.c"
-        .globl  load_common
-        .p2align        4, 0x90
-        .type   load_common, at function
-
-load_common:
-# Check that common variable GOT entry is synthesized correctly. In order to
-# prevent the optimizer from relaxing the edge, we use a movl instruction.
-# jitlink-check: decode_operand(load_common, 4) = \
-# jitlink-check:   got_addr(elf_common.o, common_data) - next_pc(load_common)
-# jitlink-check: *{8}(got_addr(elf_common.o, common_data)) = common_data
-        movl    common_data at GOTPCREL(%rip), %eax
-        ret
-.Lfunc_end0:
-        .size   load_common, .Lfunc_end0-load_common
-
-# Check that common is zero-filled.
-# jitlink-check: *{4}(common_data) = 0
-        .type   common_data, at object
-        .comm   common_data,4,4