Revert merge of r360861:

------------------------------------------------------------------------
r360861 | mstorsjo | 2019-05-15 23:49:13 -0700 (Wed, 15 May 2019) | 13 lines

[PPC64][libunwind] Fix r2 not properly restored

This change makes each unwind step inspect the instruction at the
return address and, if needed, read r2 from its saved ___location and
modify the context appropriately.

The unwind logic is able to handle both ELFv1 and ELFv2 stacks.

Reported by Bug 41050

Patch by Leandro Lupori!

Differential Revision: https://reviews.llvm.org/D59694
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llvm-svn: 365539

Author: DimitryAndric

libunwind/src/DwarfInstructions.hpp

@@ -234,31 +234,6 @@ int DwarfInstructions<A, R>::stepWithDwarf(A &addressSpace, pint_t pc,
       }
 #endif
 
-#if defined(_LIBUNWIND_TARGET_PPC64)
-#define PPC64_ELFV1_R2_LOAD_INST_ENCODING 0xe8410028u // ld r2,40(r1)
-#define PPC64_ELFV1_R2_OFFSET 40
-#define PPC64_ELFV2_R2_LOAD_INST_ENCODING 0xe8410018u // ld r2,24(r1)
-#define PPC64_ELFV2_R2_OFFSET 24
-      // If the instruction at return address is a TOC (r2) restore,
-      // then r2 was saved and needs to be restored.
-      // ELFv2 ABI specifies that the TOC Pointer must be saved at SP + 24,
-      // while in ELFv1 ABI it is saved at SP + 40.
-      if (R::getArch() == REGISTERS_PPC64 && returnAddress != 0) {
-        pint_t sp = newRegisters.getRegister(UNW_REG_SP);
-        pint_t r2 = 0;
-        switch (addressSpace.get32(returnAddress)) {
-        case PPC64_ELFV1_R2_LOAD_INST_ENCODING:
-          r2 = addressSpace.get64(sp + PPC64_ELFV1_R2_OFFSET);
-          break;
-        case PPC64_ELFV2_R2_LOAD_INST_ENCODING:
-          r2 = addressSpace.get64(sp + PPC64_ELFV2_R2_OFFSET);
-          break;
-        }
-        if (r2)
-          newRegisters.setRegister(UNW_PPC64_R2, r2);
-      }
-#endif
-
       // Return address is address after call site instruction, so setting IP to
       // that does simualates a return.
       newRegisters.setIP(returnAddress);

libunwind/src/assembly.h

@@ -35,20 +35,6 @@
 #define SEPARATOR ;
 #endif
 
-#if defined(__powerpc64__) && (!defined(_CALL_ELF) || _CALL_ELF == 1)
-#define PPC64_OPD1 .section .opd,"aw",@progbits SEPARATOR
-#define PPC64_OPD2 SEPARATOR \
-  .p2align 3 SEPARATOR \
-  .quad .Lfunc_begin0 SEPARATOR \
-  .quad .TOC.@tocbase SEPARATOR \
-  .quad 0 SEPARATOR \
-  .text SEPARATOR \
-.Lfunc_begin0:
-#else
-#define PPC64_OPD1
-#define PPC64_OPD2
-#endif
-
 #define GLUE2(a, b) a ## b
 #define GLUE(a, b) GLUE2(a, b)
 #define SYMBOL_NAME(name) GLUE(__USER_LABEL_PREFIX__, name)
@@ -109,9 +95,7 @@
   .globl SYMBOL_NAME(name) SEPARATOR                      \
   EXPORT_SYMBOL(name) SEPARATOR                           \
   SYMBOL_IS_FUNC(SYMBOL_NAME(name)) SEPARATOR             \
-  PPC64_OPD1                                              \
-  SYMBOL_NAME(name):                                      \
-  PPC64_OPD2
+  SYMBOL_NAME(name):
 
 #define DEFINE_LIBUNWIND_PRIVATE_FUNCTION(name)           \
   .globl SYMBOL_NAME(name) SEPARATOR                      \

libunwind/test/lit.cfg

@@ -23,9 +23,6 @@ config.suffixes = ['.cpp', '.s']
 # test_source_root: The root path where tests are located.
 config.test_source_root = os.path.dirname(__file__)
 
-# needed to test libunwind with code that throws exceptions
-config.enable_exceptions = True
-
 # Infer the libcxx_test_source_root for configuration import.
 # If libcxx_source_root isn't specified in the config, assume that the libcxx
 # and libunwind source directories are sibling directories.