[X86] Simplify the TSFlags checking code in EvexToVexInstPass. NFCI

The code was previously checking the L2 and L flag on 3 separate lines, treating the combination as an encoding. Instead its better to think of the L2 bit as being something that can't be done with VEX and early returning. Then we just need to check the L bit.

llvm-svn: 335015

diff --git a/llvm/lib/Target/X86/X86EvexToVex.cpp b/llvm/lib/Target/X86/X86EvexToVex.cpp
index b158042a857766510d94670ff95faa975ff62517..b71b0c6f5f679691e9e2c53ba77658d4c6468d82 100644 (file)
--- a/llvm/lib/Target/X86/X86EvexToVex.cpp
+++ b/llvm/lib/Target/X86/X86EvexToVex.cpp
@@ -248,30 +248,20 @@ bool EvexToVexInstPass::CompressEvexToVexImpl(MachineInstr &MI) const {
   if (Desc.TSFlags & (X86II::EVEX_K | X86II::EVEX_B))
     return false;
 
-  // Check for non EVEX_V512 instrs only.
-  // EVEX_V512 instr: bit EVEX_L2 = 1; bit VEX_L = 0.
-  if ((Desc.TSFlags & X86II::EVEX_L2) && !(Desc.TSFlags & X86II::VEX_L))
+  // Check for EVEX instructions with L2 set. These instructions are 512-bits
+  // and can't be converted to VEX.
+  if (Desc.TSFlags & X86II::EVEX_L2)
     return false;
 
-  // EVEX_V128 instr: bit EVEX_L2 = 0, bit VEX_L = 0.
-  bool IsEVEX_V128 =
-      (!(Desc.TSFlags & X86II::EVEX_L2) && !(Desc.TSFlags & X86II::VEX_L));
-
-  // EVEX_V256 instr: bit EVEX_L2 = 0, bit VEX_L = 1.
-  bool IsEVEX_V256 =
-      (!(Desc.TSFlags & X86II::EVEX_L2) && (Desc.TSFlags & X86II::VEX_L));
-
   unsigned NewOpc = 0;
 
-  // Check for EVEX_V256 instructions.
-  if (IsEVEX_V256) {
+  // Use the VEX.L bit to select the 128 or 256-bit table.
+  if (Desc.TSFlags & X86II::VEX_L) {
     // Search for opcode in the EvexToVex256 table.
     auto It = EvexToVex256Table.find(MI.getOpcode());
     if (It != EvexToVex256Table.end())
       NewOpc = It->second;
-  }
-  // Check for EVEX_V128 or Scalar instructions.
-  else if (IsEVEX_V128) {
+  } else {
     // Search for opcode in the EvexToVex128 table.
     auto It = EvexToVex128Table.find(MI.getOpcode());
     if (It != EvexToVex128Table.end())