Fix a bug in llvm-objdump when disassembling using the wrong default CPU

in the second slice of a Mach-O universal file.

The code in llvm-objdump in in DisassembleMachO() was getting the default
CPU then incorrectly setting into the global variable used for the -mcpu option
if that was not set.  This caused a second call to DisassembleMachO() to use
the wrong default CPU when disassembling the next slice in a Mach-O universal
file.  And would result in bad disassembly and an error message about an
recognized processor for the target:

% llvm-objdump -d -m -arch all  fat.macho-armv7s-arm64 
fat.macho-armv7s-arm64 (architecture armv7s):
(__TEXT,__text) section
armv7:
       0:	60 47 	bx	r12
fat.macho-armv7s-arm64 (architecture arm64):
'cortex-a7' is not a recognized processor for this target (ignoring processor)
'cortex-a7' is not a recognized processor for this target (ignoring processor)
(__TEXT,__text) section
___multc3:
       0:		.long	0x1e620810

rdar://34439149

llvm-svn: 313921

3 files changed, 13 insertions, 3 deletions

diff --git a/llvm/test/tools/llvm-objdump/AArch64/Inputs/fat.macho-armv7s-arm64 b/llvm/test/tools/llvm-objdump/AArch64/Inputs/fat.macho-armv7s-arm64
new file mode 100644
index 00000000000..5a61a78247a
--- /dev/null
+++ b/llvm/test/tools/llvm-objdump/AArch64/Inputs/fat.macho-armv7s-arm64
diff --git a/llvm/test/tools/llvm-objdump/AArch64/macho-fat-arm-disasm.test b/llvm/test/tools/llvm-objdump/AArch64/macho-fat-arm-disasm.test
new file mode 100644
index 00000000000..69ff25436b6
--- /dev/null
+++ b/llvm/test/tools/llvm-objdump/AArch64/macho-fat-arm-disasm.test
@@ -0,0 +1,6 @@
+RUN: llvm-objdump -d -m -no-show-raw-insn -arch all %p/Inputs/fat.macho-armv7s-arm64 | FileCheck %s
+
+CHECK: (architecture armv7s):
+CHECK: bx	r12
+CHECK: (architecture arm64):
+CHECK: fmul	d16, d0, d2
diff --git a/llvm/tools/llvm-objdump/MachODump.cpp b/llvm/tools/llvm-objdump/MachODump.cpp
index e1e42c2e218..006ba5765e7 100644
--- a/llvm/tools/llvm-objdump/MachODump.cpp
+++ b/llvm/tools/llvm-objdump/MachODump.cpp
@@ -6439,8 +6439,11 @@ static void DisassembleMachO(StringRef Filename, MachOObjectFile *MachOOF,
     // GetTarget prints out stuff.
     return;
   }
+  std::string MachOMCPU;
   if (MCPU.empty() && McpuDefault)
-    MCPU = McpuDefault;
+    MachOMCPU = McpuDefault;
+  else
+    MachOMCPU = MCPU;
 
   std::unique_ptr<const MCInstrInfo> InstrInfo(TheTarget->createMCInstrInfo());
   std::unique_ptr<const MCInstrInfo> ThumbInstrInfo;
@@ -6462,7 +6465,7 @@ static void DisassembleMachO(StringRef Filename, MachOObjectFile *MachOOF,
   std::unique_ptr<const MCAsmInfo> AsmInfo(
       TheTarget->createMCAsmInfo(*MRI, TripleName));
   std::unique_ptr<const MCSubtargetInfo> STI(
-      TheTarget->createMCSubtargetInfo(TripleName, MCPU, FeaturesStr));
+      TheTarget->createMCSubtargetInfo(TripleName, MachOMCPU, FeaturesStr));
   MCContext Ctx(AsmInfo.get(), MRI.get(), nullptr);
   std::unique_ptr<MCDisassembler> DisAsm(
       TheTarget->createMCDisassembler(*STI, Ctx));
@@ -6512,7 +6515,8 @@ static void DisassembleMachO(StringRef Filename, MachOObjectFile *MachOOF,
     ThumbAsmInfo.reset(
         ThumbTarget->createMCAsmInfo(*ThumbMRI, ThumbTripleName));
     ThumbSTI.reset(
-        ThumbTarget->createMCSubtargetInfo(ThumbTripleName, MCPU, FeaturesStr));
+        ThumbTarget->createMCSubtargetInfo(ThumbTripleName, MachOMCPU,
+                                           FeaturesStr));
     ThumbCtx.reset(new MCContext(ThumbAsmInfo.get(), ThumbMRI.get(), nullptr));
     ThumbDisAsm.reset(ThumbTarget->createMCDisassembler(*ThumbSTI, *ThumbCtx));
     MCContext *PtrThumbCtx = ThumbCtx.get();