[PPC] Disassemble little endian ppc instructions in the right byte order

PR24122. The test is simply a byte swapped version of ppc64-encoding.txt.

llvm-svn: 242288

1 files changed, 17 insertions, 8 deletions

diff --git a/llvm/lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp b/llvm/lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp
index 4799ea27c4b..93a503c3758 100644
--- a/llvm/lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp
+++ b/llvm/lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp
@@ -12,6 +12,7 @@
 #include "llvm/MC/MCFixedLenDisassembler.h"
 #include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCSubtargetInfo.h"
+#include "llvm/Support/Endian.h"
 #include "llvm/Support/TargetRegistry.h"
 
 using namespace llvm;
@@ -22,10 +23,12 @@ typedef MCDisassembler::DecodeStatus DecodeStatus;
 
 namespace {
 class PPCDisassembler : public MCDisassembler {
+  bool IsLittleEndian;
+
 public:
-  PPCDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx)
-    : MCDisassembler(STI, Ctx) {}
-  ~PPCDisassembler() override {}
+  PPCDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx,
+                  bool IsLittleEndian)
+      : MCDisassembler(STI, Ctx), IsLittleEndian(IsLittleEndian) {}
 
   DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size,
                               ArrayRef<uint8_t> Bytes, uint64_t Address,
@@ -37,7 +40,13 @@ public:
 static MCDisassembler *createPPCDisassembler(const Target &T,
                                              const MCSubtargetInfo &STI,
                                              MCContext &Ctx) {
-  return new PPCDisassembler(STI, Ctx);
+  return new PPCDisassembler(STI, Ctx, /*IsLittleEndian=*/false);
+}
+
+static MCDisassembler *createPPCLEDisassembler(const Target &T,
+                                               const MCSubtargetInfo &STI,
+                                               MCContext &Ctx) {
+  return new PPCDisassembler(STI, Ctx, /*IsLittleEndian=*/true);
 }
 
 extern "C" void LLVMInitializePowerPCDisassembler() {
@@ -47,7 +56,7 @@ extern "C" void LLVMInitializePowerPCDisassembler() {
   TargetRegistry::RegisterMCDisassembler(ThePPC64Target,
                                          createPPCDisassembler);
   TargetRegistry::RegisterMCDisassembler(ThePPC64LETarget,
-                                         createPPCDisassembler);
+                                         createPPCLEDisassembler);
 }
 
 // FIXME: These can be generated by TableGen from the existing register
@@ -383,9 +392,9 @@ DecodeStatus PPCDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
     return MCDisassembler::Fail;
   }
 
-  // The instruction is big-endian encoded.
-  uint32_t Inst =
-      (Bytes[0] << 24) | (Bytes[1] << 16) | (Bytes[2] << 8) | (Bytes[3] << 0);
+  // Read the instruction in the proper endianness.
+  uint32_t Inst = IsLittleEndian ? support::endian::read32le(Bytes.data())
+                                 : support::endian::read32be(Bytes.data());
 
   if (STI.getFeatureBits()[PPC::FeatureQPX]) {
     DecodeStatus result =