From 61f607e1dfdfe996e5cf8263564398670dc40369 Mon Sep 17 00:00:00 2001
From: flobernd <flobernd@users.noreply.github.com>
Date: Wed, 17 Jan 2018 00:31:32 +0100
Subject: [PATCH] Minor optimizations and bugfixes

- Fixed `XCHG R8, RAX` falsely beeing decoded as `NOP`
- Fixed `EVEX/MVEX.R'` not beeing ignored in 16- and 32-bit mode
- Removed some unnecessary conditions from operand-action related code
---
 src/Decoder.c                   | 30 ++++++++++++++++++++++++++----
 src/Generated/DecoderTables.inc |  2 +-
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/src/Decoder.c b/src/Decoder.c
index aa0b0dc..ea41ddc 100644
--- a/src/Decoder.c
+++ b/src/Decoder.c
@@ -1994,7 +1994,7 @@ FinalizeOperand:
 
 #if !defined(ZYDIS_DISABLE_EVEX) || !defined(ZYDIS_DISABLE_MVEX)
     // Fix operand-action for EVEX instructions with merge-mask
-    if (((instruction->encoding == ZYDIS_INSTRUCTION_ENCODING_EVEX) || 
+    /*if (((instruction->encoding == ZYDIS_INSTRUCTION_ENCODING_EVEX) || 
          (instruction->encoding == ZYDIS_INSTRUCTION_ENCODING_MVEX)) && 
         (instruction->avx.mask.mode == ZYDIS_MASK_MODE_MERGE) &&
         (instruction->operandCount >= 3) &&
@@ -2027,6 +2027,28 @@ FinalizeOperand:
         default:
             break;
         }
+    }*/
+    if (instruction->avx.mask.reg && (instruction->avx.mask.mode == ZYDIS_MASK_MODE_MERGE) && 
+        !instruction->avx.mask.isControlMask)
+    {
+        ZYDIS_ASSERT(instruction->operandCount >= 2);
+        switch (instruction->operands[0].action)
+        {
+        case ZYDIS_OPERAND_ACTION_WRITE:
+            if (instruction->operands[0].type == ZYDIS_OPERAND_TYPE_MEMORY)
+            {
+                instruction->operands[0].action = ZYDIS_OPERAND_ACTION_CONDWRITE;
+            } else
+            {
+                instruction->operands[0].action = ZYDIS_OPERAND_ACTION_READ_CONDWRITE;
+            }
+            break;
+        case ZYDIS_OPERAND_ACTION_READWRITE:
+            instruction->operands[0].action = ZYDIS_OPERAND_ACTION_READ_CONDWRITE;
+            break;
+        default:
+            break;
+        }
     }
 #endif
 
@@ -4152,7 +4174,7 @@ static ZydisStatus ZydisCheckErrorConditions(ZydisDecoderContext* context,
     case ZYDIS_REG_CONSTRAINTS_NONE:    
         break;
     case ZYDIS_REG_CONSTRAINTS_GPR:
-        if (context->cache.R2)
+        if ((context->decoder->machineMode == ZYDIS_MACHINE_MODE_LONG_64) && context->cache.R2)
         {
             return ZYDIS_STATUS_BAD_REGISTER;
         }
@@ -4198,8 +4220,8 @@ static ZydisStatus ZydisCheckErrorConditions(ZydisDecoderContext* context,
         }
         break; 
     case ZYDIS_REG_CONSTRAINTS_MASK:
-        // TODO: ZYDIS_ASSERT(!context->cache.R2) ?
-        if (context->cache.R || context->cache.R2)
+        if ((context->decoder->machineMode == ZYDIS_MACHINE_MODE_LONG_64) && 
+            (context->cache.R || context->cache.R2))
         {
             return ZYDIS_STATUS_BAD_REGISTER;
         }
diff --git a/src/Generated/DecoderTables.inc b/src/Generated/DecoderTables.inc
index 5785eb9..e84368b 100644
--- a/src/Generated/DecoderTables.inc
+++ b/src/Generated/DecoderTables.inc
@@ -2620,7 +2620,7 @@ const ZydisDecoderTreeNode filtersMandatoryPrefix[][5] =
     { ZYDIS_FILTER(ZYDIS_NODETYPE_FILTER_OPERAND_SIZE, 0x5), ZYDIS_INVALID, ZYDIS_INVALID, ZYDIS_FILTER(ZYDIS_NODETYPE_FILTER_OPERAND_SIZE, 0x6), ZYDIS_FILTER(ZYDIS_NODETYPE_FILTER_OPERAND_SIZE, 0x7) }, 
     { ZYDIS_DEFINITION(0x0, 0x3E4), ZYDIS_INVALID, ZYDIS_INVALID, ZYDIS_DEFINITION(0x0, 0x3E5), ZYDIS_DEFINITION(0x0, 0x3E6) }, 
     { ZYDIS_FILTER(ZYDIS_NODETYPE_FILTER_OPERAND_SIZE, 0x8), ZYDIS_INVALID, ZYDIS_INVALID, ZYDIS_FILTER(ZYDIS_NODETYPE_FILTER_OPERAND_SIZE, 0x9), ZYDIS_FILTER(ZYDIS_NODETYPE_FILTER_OPERAND_SIZE, 0xA) }, 
-    { ZYDIS_DEFINITION(0x0, 0x390), ZYDIS_FILTER(ZYDIS_NODETYPE_FILTER_REX_B, 0x0), ZYDIS_INVALID, ZYDIS_DEFINITION(0x0, 0x436), ZYDIS_INVALID }, 
+    { ZYDIS_FILTER(ZYDIS_NODETYPE_FILTER_REX_B, 0x0), ZYDIS_INVALID, ZYDIS_INVALID, ZYDIS_DEFINITION(0x0, 0x436), ZYDIS_INVALID }, 
     { ZYDIS_DEFINITION(0x0, 0x353), ZYDIS_INVALID, ZYDIS_INVALID, ZYDIS_DEFINITION(0x0, 0x354), ZYDIS_DEFINITION(0x0, 0x355) }, 
     { ZYDIS_FILTER(ZYDIS_NODETYPE_FILTER_OPERAND_SIZE, 0x11), ZYDIS_INVALID, ZYDIS_INVALID, ZYDIS_FILTER(ZYDIS_NODETYPE_FILTER_OPERAND_SIZE, 0x12), ZYDIS_FILTER(ZYDIS_NODETYPE_FILTER_OPERAND_SIZE, 0x13) }, 
     { ZYDIS_DEFINITION(0x0, 0xEB), ZYDIS_INVALID, ZYDIS_INVALID, ZYDIS_DEFINITION(0x0, 0xEC), ZYDIS_DEFINITION(0x0, 0xED) },