[llvm-commits] [llvm] r100403 - /llvm/trunk/lib/Target/ARM/Disassembler/ARMDisassembler.cpp

[Johnny Chen]

Author: johnny
Date: Sun Apr  4 23:46:17 2010
New Revision: 100403

URL: http://llvm.org/viewvc/llvm-project?rev=100403&view=rev
Log:
The disassembler impl. of MCDisassembler::getInstruction() was using the pattern
  uint32_t insn;
  MemoryObject.readBytes(Address, 4, (uint8_t*)&insn, NULL)

to read 4 bytes of memory contents into a 32-bit uint variable.  This leaves the
interpretation of byte order up to the host machine and causes PPC test cases of
arm-tests, neon-tests, and thumb-tests to fail.  Fixed to use a byte array for
reading the memory contents and shift the bytes into place for the 32-bit uint
variable in the ARM case and 16-bit halfword in the Thumb case.

Modified:
    llvm/trunk/lib/Target/ARM/Disassembler/ARMDisassembler.cpp

Modified: llvm/trunk/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/Disassembler/ARMDisassembler.cpp?rev=100403&r1=100402&r2=100403&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/Disassembler/ARMDisassembler.cpp (original)
+++ llvm/trunk/lib/Target/ARM/Disassembler/ARMDisassembler.cpp Sun Apr  4 23:46:17 2010
@@ -380,11 +380,18 @@
                                      raw_ostream &os) const {
   // The machine instruction.
   uint32_t insn;
+  uint8_t bytes[4];
 
   // We want to read exactly 4 bytes of data.
-  if (Region.readBytes(Address, 4, (uint8_t*)&insn, NULL) == -1)
+  if (Region.readBytes(Address, 4, (uint8_t*)bytes, NULL) == -1)
     return false;
 
+  // Encoded as a small-endian 32-bit word in the stream.
+  insn = (bytes[3] << 24) |
+         (bytes[2] << 16) |
+         (bytes[1] <<  8) |
+         (bytes[0] <<  0);
+    
   unsigned Opcode = decodeARMInstruction(insn);
   ARMFormat Format = ARMFormats[Opcode];
   Size = 4;
@@ -414,9 +421,15 @@
                                        const MemoryObject &Region,
                                        uint64_t Address,
                                        raw_ostream &os) const {
-  // The machine instruction.
+  // The Thumb instruction stream is a sequence of halhwords.
+
+  // This represents the first halfword as well as the machine instruction
+  // passed to decodeThumbInstruction().  For 16-bit Thumb instruction, the top
+  // halfword of insn is 0x00 0x00; otherwise, the first halfword is moved to
+  // the top half followed by the second halfword.
   uint32_t insn = 0;
-  uint32_t insn1 = 0;
+  // Possible second halfword.
+  uint16_t insn1 = 0;
 
   // A6.1 Thumb instruction set encoding
   //
@@ -429,9 +442,12 @@
   // Otherwise, the halfword is a 16-bit instruction.
 
   // Read 2 bytes of data first.
-  if (Region.readBytes(Address, 2, (uint8_t*)&insn, NULL) == -1)
+  uint8_t bytes[2];
+  if (Region.readBytes(Address, 2, (uint8_t*)bytes, NULL) == -1)
     return false;
 
+  // Encoded as a small-endian 16-bit halfword in the stream.
+  insn = (bytes[1] << 8) | bytes[0];
   unsigned bits15_11 = slice(insn, 15, 11);
   bool IsThumb2 = false;
 
@@ -439,8 +455,10 @@
   // { 0b11101 /* 0x1D */, 0b11110 /* 0x1E */, ob11111 /* 0x1F */ }.
   if (bits15_11 == 0x1D || bits15_11 == 0x1E || bits15_11 == 0x1F) {
     IsThumb2 = true;
-    if (Region.readBytes(Address + 2, 2, (uint8_t*)&insn1, NULL) == -1)
+    if (Region.readBytes(Address + 2, 2, (uint8_t*)bytes, NULL) == -1)
       return false;
+    // Encoded as a small-endian 16-bit halfword in the stream.
+    insn1 = (bytes[1] << 8) | bytes[0];
     insn = (insn << 16 | insn1);
   }