[PATCH] [mips] [IAS] Add support for LASym with identical source and destination register operands.

[Toma Tabacu]

Replaced the UseAT variable with its corresponding condition, as it was being used only once.
Put the "SrcReg != Mips::NoRegister" condition in a variable, as it is now used twice.
Shortened the name of IntermediateDstReg to TmpReg.
Rebased on top of the new http://reviews.llvm.org/D9523 and http://reviews.llvm.org/D9348.
Removed unnecessary dependencies on other patches.


http://reviews.llvm.org/D9366

Files:
  lib/Target/Mips/AsmParser/MipsAsmParser.cpp
  test/MC/Mips/mips-expansions.s

Index: lib/Target/Mips/AsmParser/MipsAsmParser.cpp
===================================================================
--- lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -1971,6 +1971,19 @@
   const MCSymbolRefExpr *LoExpr =
       MCSymbolRefExpr::create(Symbol->getSymbol().getName(),
                               MCSymbolRefExpr::VK_Mips_ABS_LO, getContext());
+
+  bool UseSrcReg = SrcReg != Mips::NoRegister;
+
+  unsigned ATReg = 0;
+  if (UseSrcReg && (DstReg == SrcReg)) {
+    // At this point we need AT to perform the expansions and we exit if it is
+    // not available.
+    ATReg = getATReg(IDLoc);
+    if (!ATReg)
+      return true;
+  }
+  unsigned TmpReg = (ATReg != 0) ? ATReg : DstReg;
+
   if (!Is32BitSym) {
     // If it's a 64-bit architecture, expand to:
     // la d,sym => lui  d,highest(sym)
@@ -1987,31 +2000,31 @@
                                 MCSymbolRefExpr::VK_Mips_HIGHER, getContext());
 
     tmpInst.setOpcode(Mips::LUi);
-    tmpInst.addOperand(MCOperand::createReg(DstReg));
+    tmpInst.addOperand(MCOperand::createReg(TmpReg));
     tmpInst.addOperand(MCOperand::createExpr(HighestExpr));
     Instructions.push_back(tmpInst);
 
-    createLShiftOri<0>(MCOperand::createExpr(HigherExpr), DstReg, SMLoc(),
+    createLShiftOri<0>(MCOperand::createExpr(HigherExpr), TmpReg, SMLoc(),
                        Instructions);
-    createLShiftOri<16>(MCOperand::createExpr(HiExpr), DstReg, SMLoc(),
+    createLShiftOri<16>(MCOperand::createExpr(HiExpr), TmpReg, SMLoc(),
                         Instructions);
-    createLShiftOri<16>(MCOperand::createExpr(LoExpr), DstReg, SMLoc(),
+    createLShiftOri<16>(MCOperand::createExpr(LoExpr), TmpReg, SMLoc(),
                         Instructions);
   } else {
     // Otherwise, expand to:
     // la d,sym => lui  d,hi16(sym)
     //             ori  d,d,lo16(sym)
     tmpInst.setOpcode(Mips::LUi);
-    tmpInst.addOperand(MCOperand::createReg(DstReg));
+    tmpInst.addOperand(MCOperand::createReg(TmpReg));
     tmpInst.addOperand(MCOperand::createExpr(HiExpr));
     Instructions.push_back(tmpInst);
 
-    createLShiftOri<0>(MCOperand::createExpr(LoExpr), DstReg, SMLoc(),
+    createLShiftOri<0>(MCOperand::createExpr(LoExpr), TmpReg, SMLoc(),
                        Instructions);
   }
 
-  if (SrcReg != Mips::NoRegister)
-    createAddu(DstReg, DstReg, SrcReg, Instructions);
+  if (UseSrcReg)
+    createAddu(DstReg, TmpReg, SrcReg, Instructions);
 
   return false;
 }
Index: test/MC/Mips/mips-expansions.s
===================================================================
--- test/MC/Mips/mips-expansions.s
+++ test/MC/Mips/mips-expansions.s
@@ -44,6 +44,12 @@
 # CHECK: ori  $8, $8, %lo(symbol)    # encoding: [A,A,0x08,0x35]
 # CHECK:                             #   fixup A - offset: 0, value: symbol at ABS_LO, kind: fixup_Mips_LO16
 # CHECK: addu $8, $8, $9             # encoding: [0x21,0x40,0x09,0x01]
+  la $8, symbol($8)
+# CHECK: lui  $1, %hi(symbol)        # encoding: [A,A,0x01,0x3c]
+# CHECK:                             #   fixup A - offset: 0, value: symbol at ABS_HI, kind: fixup_Mips_HI16
+# CHECK: ori  $1, $1, %lo(symbol)    # encoding: [A,A,0x21,0x34]
+# CHECK:                             #   fixup A - offset: 0, value: symbol at ABS_LO, kind: fixup_Mips_LO16
+# CHECK: addu $8, $1, $8             # encoding: [0x21,0x40,0x28,0x00]
 
 # LW/SW and LDC1/SDC1 of symbol address, done by MipsAsmParser::expandMemInst():
   .set noat

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