[llvm] r219194 - [X86] Fix a bug where the disassembler was ignoring the VEX.W bit in 32-bit mode for certain instructions it shouldn't.

[Craig Topper]

Author: ctopper
Date: Tue Oct  7 02:29:50 2014
New Revision: 219194

URL: http://llvm.org/viewvc/llvm-project?rev=219194&view=rev
Log:
[X86] Fix a bug where the disassembler was ignoring the VEX.W bit in 32-bit mode for certain instructions it shouldn't.

Unfortunately, this isn't easy to fix since there's no simple way to figure out from the disassembler tables whether the W-bit is being used to select a 64-bit GPR or if its a required part of the opcode. The fix implemented here just looks for "64" in the instruction name and ignores the W-bit in 32-bit mode if its present.

Fixes PR21169.

Modified:
    llvm/trunk/lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp
    llvm/trunk/test/MC/Disassembler/X86/x86-32.txt

Modified: llvm/trunk/lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp?rev=219194&r1=219193&r2=219194&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp (original)
+++ llvm/trunk/lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp Tue Oct  7 02:29:50 2014
@@ -852,6 +852,22 @@ static bool is16BitEquivalent(const char
 }
 
 /*
+ * is64Bit - Determines whether this instruction is a 64-bit instruction.
+ *
+ * @param name - The instruction that is not 16-bit
+ */
+static bool is64Bit(const char* name) {
+  off_t i;
+
+  for (i = 0;; ++i) {
+    if (name[i] == '\0')
+      return false;
+    if (name[i] == '6' && name[i+1] == '4')
+      return true;
+  }
+}
+
+/*
  * getID - Determines the ID of an instruction, consuming the ModR/M byte as
  *   appropriate for extended and escape opcodes.  Determines the attributes and
  *   context for the instruction before doing so.
@@ -983,6 +999,37 @@ static int getID(struct InternalInstruct
 
   /* The following clauses compensate for limitations of the tables. */
 
+  if (insn->mode != MODE_64BIT &&
+      insn->vectorExtensionType != TYPE_NO_VEX_XOP) {
+    /*
+     * The tables can't distinquish between cases where the W-bit is used to
+     * select register size and cases where its a required part of the opcode.
+     */
+    if ((insn->vectorExtensionType == TYPE_EVEX &&
+         wFromEVEX3of4(insn->vectorExtensionPrefix[2])) ||
+        (insn->vectorExtensionType == TYPE_VEX_3B &&
+         wFromVEX3of3(insn->vectorExtensionPrefix[2])) ||
+        (insn->vectorExtensionType == TYPE_XOP &&
+         wFromXOP3of3(insn->vectorExtensionPrefix[2]))) {
+
+      uint16_t instructionIDWithREXW;
+      if (getIDWithAttrMask(&instructionIDWithREXW,
+                            insn, attrMask | ATTR_REXW)) {
+        insn->instructionID = instructionID;
+        insn->spec = specifierForUID(instructionID);
+        return 0;
+      }
+
+      const char *SpecName = GetInstrName(instructionIDWithREXW, miiArg);
+      // If not a 64-bit instruction. Switch the opcode.
+      if (!is64Bit(SpecName)) {
+        insn->instructionID = instructionIDWithREXW;
+        insn->spec = specifierForUID(instructionIDWithREXW);
+        return 0;
+      }
+    }
+  }
+
   if ((insn->mode == MODE_16BIT || insn->prefixPresent[0x66]) &&
       !(attrMask & ATTR_OPSIZE)) {
     /*

Modified: llvm/trunk/test/MC/Disassembler/X86/x86-32.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/Disassembler/X86/x86-32.txt?rev=219194&r1=219193&r2=219194&view=diff
==============================================================================
--- llvm/trunk/test/MC/Disassembler/X86/x86-32.txt (original)
+++ llvm/trunk/test/MC/Disassembler/X86/x86-32.txt Tue Oct  7 02:29:50 2014
@@ -711,3 +711,6 @@
 
 # CHECK: movq %mm0, %mm1
 0x0f 0x7f 0xc1
+
+# CHECK: vpermq $-18, %ymm2, %ymm2
+0xc4 0xe3 0xfd 0x00 0xd2 0xee