From d9610b4a56c532614545eef5995362e99b776535 Mon Sep 17 00:00:00 2001
From: Shengchen Kan <shengchen.kan@intel.com>
Date: Wed, 17 May 2023 22:45:07 +0800
Subject: [PATCH] [X86][MC] Move the code about MOVSX encoding optimization to
 X86EncodingOptimization.cpp, NFCI

---
 .../X86/MCTargetDesc/X86EncodingOptimization.cpp   | 22 ++++++++++++
 .../X86/MCTargetDesc/X86EncodingOptimization.h     |  1 +
 llvm/lib/Target/X86/X86MCInstLower.cpp             | 39 ++--------------------
 3 files changed, 26 insertions(+), 36 deletions(-)

diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimization.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimization.cpp
index 5aab27b..43a93cb 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimization.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimization.cpp
@@ -230,6 +230,7 @@ bool X86::optimizeVPCMPWithImmediateOneOrSix(MCInst &MI) {
     FROM_TO(VPCMPWZrmik, VPCMPEQWZrmk, VPCMPGTWZrmk)
     FROM_TO(VPCMPWZrri, VPCMPEQWZrr, VPCMPGTWZrr)
     FROM_TO(VPCMPWZrrik, VPCMPEQWZrrk, VPCMPGTWZrrk)
+#undef FROM_TO
   }
   MCOperand &LastOp = MI.getOperand(MI.getNumOperands() - 1);
   int64_t Imm = LastOp.getImm();
@@ -244,3 +245,24 @@ bool X86::optimizeVPCMPWithImmediateOneOrSix(MCInst &MI) {
   MI.erase(&LastOp);
   return true;
 }
+
+bool X86::optimizeMOVSX(MCInst &MI) {
+  unsigned NewOpc;
+#define FROM_TO(FROM, TO, R0, R1)                                              \
+  case X86::FROM:                                                              \
+    if (MI.getOperand(0).getReg() != X86::R0 ||                                \
+        MI.getOperand(1).getReg() != X86::R1)                                  \
+      return false;                                                            \
+    NewOpc = X86::TO;                                                          \
+    break;
+  switch (MI.getOpcode()) {
+  default:
+    return false;
+    FROM_TO(MOVSX16rr8, CBW, AX, AL)     // movsbw %al, %ax   --> cbtw
+    FROM_TO(MOVSX32rr16, CWDE, EAX, AX)  // movswl %ax, %eax  --> cwtl
+    FROM_TO(MOVSX64rr32, CDQE, RAX, EAX) // movslq %eax, %rax --> cltq
+  }
+  MI.clear();
+  MI.setOpcode(NewOpc);
+  return true;
+}
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimization.h b/llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimization.h
index 42c1239..1e085e9 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimization.h
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimization.h
@@ -19,6 +19,7 @@ namespace X86 {
 bool optimizeInstFromVEX3ToVEX2(MCInst &MI, const MCInstrDesc &Desc);
 bool optimizeShiftRotateWithImmediateOne(MCInst &MI);
 bool optimizeVPCMPWithImmediateOneOrSix(MCInst &MI);
+bool optimizeMOVSX(MCInst &MI);
 } // namespace X86
 } // namespace llvm
 #endif
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index cf5d4f9..c68a9d26 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -343,34 +343,6 @@ static void SimplifyShortImmForm(MCInst &Inst, unsigned Opcode) {
   Inst.addOperand(Saved);
 }
 
-/// If a movsx instruction has a shorter encoding for the used register
-/// simplify the instruction to use it instead.
-static void SimplifyMOVSX(MCInst &Inst) {
-  unsigned NewOpcode = 0;
-  unsigned Op0 = Inst.getOperand(0).getReg(), Op1 = Inst.getOperand(1).getReg();
-  switch (Inst.getOpcode()) {
-  default:
-    llvm_unreachable("Unexpected instruction!");
-  case X86::MOVSX16rr8: // movsbw %al, %ax   --> cbtw
-    if (Op0 == X86::AX && Op1 == X86::AL)
-      NewOpcode = X86::CBW;
-    break;
-  case X86::MOVSX32rr16: // movswl %ax, %eax  --> cwtl
-    if (Op0 == X86::EAX && Op1 == X86::AX)
-      NewOpcode = X86::CWDE;
-    break;
-  case X86::MOVSX64rr32: // movslq %eax, %rax --> cltq
-    if (Op0 == X86::RAX && Op1 == X86::EAX)
-      NewOpcode = X86::CDQE;
-    break;
-  }
-
-  if (NewOpcode != 0) {
-    Inst = MCInst();
-    Inst.setOpcode(NewOpcode);
-  }
-}
-
 /// Simplify things like MOV32rm to MOV32o32a.
 static void SimplifyShortMoveForm(X86AsmPrinter &Printer, MCInst &Inst,
                                   unsigned Opcode) {
@@ -511,6 +483,9 @@ void X86MCInstLower::Lower(const MachineInstr *MI, MCInst &OutMI) const {
   if (X86::optimizeVPCMPWithImmediateOneOrSix(OutMI))
     return;
 
+  if (X86::optimizeMOVSX(OutMI))
+    return;
+
   // Handle a few special cases to eliminate operand modifiers.
   switch (OutMI.getOpcode()) {
   case X86::LEA64_32r:
@@ -703,14 +678,6 @@ void X86MCInstLower::Lower(const MachineInstr *MI, MCInst &OutMI) const {
     SimplifyShortImmForm(OutMI, NewOpc);
     break;
   }
-
-  // Try to shrink some forms of movsx.
-  case X86::MOVSX16rr8:
-  case X86::MOVSX32rr16:
-  case X86::MOVSX64rr32:
-    SimplifyMOVSX(OutMI);
-    break;
-
   case X86::VCMPPDrri:
   case X86::VCMPPDYrri:
   case X86::VCMPPSrri:
-- 
2.7.4