[PATCH] D111538: [X86] Prefer VEX encoding in X86 assembler.

[LuoYuanke via Phabricator via llvm-commits]

LuoYuanke updated this revision to Diff 379339.
LuoYuanke added a comment.

Address Shengchen's comments.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D111538/new/

https://reviews.llvm.org/D111538

Files:
  llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
  llvm/utils/TableGen/AsmMatcherEmitter.cpp


Index: llvm/utils/TableGen/AsmMatcherEmitter.cpp
===================================================================
--- llvm/utils/TableGen/AsmMatcherEmitter.cpp
+++ llvm/utils/TableGen/AsmMatcherEmitter.cpp
@@ -636,6 +636,14 @@
     if (RequiredFeatures.size() != RHS.RequiredFeatures.size())
       return RequiredFeatures.size() > RHS.RequiredFeatures.size();
 
+    // For X86 AVX/AVX512 instructions, we prefer vex encoding because the
+    // vex encoding size is smaller. Since X86InstrSSE.td is included ahead
+    // of X86InstrAVX512.td, the AVX instruction ID is less than AVX512 ID.
+    // We use the ID to sort AVX instruction before AVX512 instruction in
+    // matching table.
+    if (TheDef->isSubClassOf("X86Inst"))
+      return TheDef->getID() < RHS.TheDef->getID();
+
     return false;
   }
 
Index: llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
===================================================================
--- llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -4270,24 +4270,6 @@
        ForcedVEXEncoding != VEXEncoding_VEX3))
     return Match_Unsupported;
 
-  // These instructions match ambiguously with their VEX encoded counterparts
-  // and appear first in the matching table. Reject them unless we're forcing
-  // EVEX encoding.
-  // FIXME: We really need a way to break the ambiguity.
-  switch (Opc) {
-  case X86::VCVTSD2SIZrm_Int:
-  case X86::VCVTSD2SI64Zrm_Int:
-  case X86::VCVTSS2SIZrm_Int:
-  case X86::VCVTSS2SI64Zrm_Int:
-  case X86::VCVTTSD2SIZrm:   case X86::VCVTTSD2SIZrm_Int:
-  case X86::VCVTTSD2SI64Zrm: case X86::VCVTTSD2SI64Zrm_Int:
-  case X86::VCVTTSS2SIZrm:   case X86::VCVTTSS2SIZrm_Int:
-  case X86::VCVTTSS2SI64Zrm: case X86::VCVTTSS2SI64Zrm_Int:
-    if (ForcedVEXEncoding != VEXEncoding_EVEX)
-      return Match_Unsupported;
-    break;
-  }
-
   return Match_Success;
 }
 


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