[mips] Add assembler support for the "la $reg,symbol" pseudo-instruction.

Summary:
This pseudo-instruction allows the programmer to load an address from a symbolic expression into a register.

Patch by David Chisnall.
His work was sponsored by: DARPA, AFRL

I've made some minor changes to the original, such as improving the formatting and adding some comments, and I've also added a test case.

Reviewers: dsanders

Reviewed By: dsanders

Differential Revision: http://reviews.llvm.org/D4808

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215630 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/Mips/AsmParser/MipsAsmParser.cpp b/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
index c0d830eaad5f3096d94143668f9f1aec19cd7cbe..0fabbe2e720dfae1fe81436cc127fb0018cf0ec2 100644 (file)
--- a/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ b/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -148,6 +148,9 @@ class MipsAsmParser : public MCTargetAsmParser {
   bool expandLoadAddressReg(MCInst &Inst, SMLoc IDLoc,
                             SmallVectorImpl<MCInst> &Instructions);
 
+  void expandLoadAddressSym(MCInst &Inst, SMLoc IDLoc,
+                            SmallVectorImpl<MCInst> &Instructions);
+
   void expandMemInst(MCInst &Inst, SMLoc IDLoc,
                      SmallVectorImpl<MCInst> &Instructions, bool isLoad,
                      bool isImmOpnd);
@@ -1103,8 +1106,8 @@ bool MipsAsmParser::expandInstruction(MCInst &Inst, SMLoc IDLoc,
 }
 
 namespace {
-template <int Shift, bool PerformShift>
-void createShiftOr(int64_t Value, unsigned RegNo, SMLoc IDLoc,
+template <bool PerformShift>
+void createShiftOr(MCOperand Operand, unsigned RegNo, SMLoc IDLoc,
                    SmallVectorImpl<MCInst> &Instructions) {
   MCInst tmpInst;
   if (PerformShift) {
@@ -1119,11 +1122,18 @@ void createShiftOr(int64_t Value, unsigned RegNo, SMLoc IDLoc,
   tmpInst.setOpcode(Mips::ORi);
   tmpInst.addOperand(MCOperand::CreateReg(RegNo));
   tmpInst.addOperand(MCOperand::CreateReg(RegNo));
-  tmpInst.addOperand(
-      MCOperand::CreateImm(((Value & (0xffffLL << Shift)) >> Shift)));
+  tmpInst.addOperand(Operand);
   tmpInst.setLoc(IDLoc);
   Instructions.push_back(tmpInst);
 }
+
+template <int Shift, bool PerformShift>
+void createShiftOr(int64_t Value, unsigned RegNo, SMLoc IDLoc,
+                   SmallVectorImpl<MCInst> &Instructions) {
+  createShiftOr<PerformShift>(
+      MCOperand::CreateImm(((Value & (0xffffLL << Shift)) >> Shift)), RegNo,
+      IDLoc, Instructions);
+}
 }
 
 bool MipsAsmParser::expandLoadImm(MCInst &Inst, SMLoc IDLoc,
@@ -1228,7 +1238,12 @@ MipsAsmParser::expandLoadAddressReg(MCInst &Inst, SMLoc IDLoc,
                                     SmallVectorImpl<MCInst> &Instructions) {
   MCInst tmpInst;
   const MCOperand &ImmOp = Inst.getOperand(2);
-  assert(ImmOp.isImm() && "expected immediate operand kind");
+  assert((ImmOp.isImm() || ImmOp.isExpr()) &&
+         "expected immediate operand kind");
+  if (!ImmOp.isImm()) {
+    expandLoadAddressSym(Inst, IDLoc, Instructions);
+    return false;
+  }
   const MCOperand &SrcRegOp = Inst.getOperand(1);
   assert(SrcRegOp.isReg() && "expected register operand kind");
   const MCOperand &DstRegOp = Inst.getOperand(0);
@@ -1272,7 +1287,12 @@ MipsAsmParser::expandLoadAddressImm(MCInst &Inst, SMLoc IDLoc,
                                     SmallVectorImpl<MCInst> &Instructions) {
   MCInst tmpInst;
   const MCOperand &ImmOp = Inst.getOperand(1);
-  assert(ImmOp.isImm() && "expected immediate operand kind");
+  assert((ImmOp.isImm() || ImmOp.isExpr()) &&
+         "expected immediate operand kind");
+  if (!ImmOp.isImm()) {
+    expandLoadAddressSym(Inst, IDLoc, Instructions);
+    return false;
+  }
   const MCOperand &RegOp = Inst.getOperand(0);
   assert(RegOp.isReg() && "expected register operand kind");
   int ImmValue = ImmOp.getImm();
@@ -1302,6 +1322,71 @@ MipsAsmParser::expandLoadAddressImm(MCInst &Inst, SMLoc IDLoc,
   return false;
 }
 
+void
+MipsAsmParser::expandLoadAddressSym(MCInst &Inst, SMLoc IDLoc,
+                                    SmallVectorImpl<MCInst> &Instructions) {
+  // FIXME: If we do have a valid at register to use, we should generate a
+  // slightly shorter sequence here.
+  MCInst tmpInst;
+  int ExprOperandNo = 1;
+  // Sometimes the assembly parser will get the immediate expression as
+  // a $zero + an immediate.
+  if (Inst.getNumOperands() == 3) {
+    assert(Inst.getOperand(1).getReg() ==
+           (isGP64bit() ? Mips::ZERO_64 : Mips::ZERO));
+    ExprOperandNo = 2;
+  }
+  const MCOperand &SymOp = Inst.getOperand(ExprOperandNo);
+  assert(SymOp.isExpr() && "expected symbol operand kind");
+  const MCOperand &RegOp = Inst.getOperand(0);
+  unsigned RegNo = RegOp.getReg();
+  const MCSymbolRefExpr *Symbol = cast<MCSymbolRefExpr>(SymOp.getExpr());
+  const MCSymbolRefExpr *HiExpr =
+      MCSymbolRefExpr::Create(Symbol->getSymbol().getName(),
+                              MCSymbolRefExpr::VK_Mips_ABS_HI, getContext());
+  const MCSymbolRefExpr *LoExpr =
+      MCSymbolRefExpr::Create(Symbol->getSymbol().getName(),
+                              MCSymbolRefExpr::VK_Mips_ABS_LO, getContext());
+  if (isGP64bit()) {
+    // If it's a 64-bit architecture, expand to:
+    // la d,sym => lui  d,highest(sym)
+    //             ori  d,d,higher(sym)
+    //             dsll d,d,16
+    //             ori  d,d,hi16(sym)
+    //             dsll d,d,16
+    //             ori  d,d,lo16(sym)
+    const MCSymbolRefExpr *HighestExpr =
+        MCSymbolRefExpr::Create(Symbol->getSymbol().getName(),
+                                MCSymbolRefExpr::VK_Mips_HIGHEST, getContext());
+    const MCSymbolRefExpr *HigherExpr =
+        MCSymbolRefExpr::Create(Symbol->getSymbol().getName(),
+                                MCSymbolRefExpr::VK_Mips_HIGHER, getContext());
+
+    tmpInst.setOpcode(Mips::LUi);
+    tmpInst.addOperand(MCOperand::CreateReg(RegNo));
+    tmpInst.addOperand(MCOperand::CreateExpr(HighestExpr));
+    Instructions.push_back(tmpInst);
+
+    createShiftOr<false>(MCOperand::CreateExpr(HigherExpr), RegNo, SMLoc(),
+                         Instructions);
+    createShiftOr<true>(MCOperand::CreateExpr(HiExpr), RegNo, SMLoc(),
+                        Instructions);
+    createShiftOr<true>(MCOperand::CreateExpr(LoExpr), RegNo, 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(RegNo));
+    tmpInst.addOperand(MCOperand::CreateExpr(HiExpr));
+    Instructions.push_back(tmpInst);
+
+    createShiftOr<false>(MCOperand::CreateExpr(LoExpr), RegNo, SMLoc(),
+                         Instructions);
+  }
+}
+
 void MipsAsmParser::expandMemInst(MCInst &Inst, SMLoc IDLoc,
                                   SmallVectorImpl<MCInst> &Instructions,
                                   bool isLoad, bool isImmOpnd) {

diff --git a/test/MC/Mips/mips-expansions.s b/test/MC/Mips/mips-expansions.s
index f0a04a5a251555910e37158377a1be13c681201e..bdc76fb44fa14709745d99b345d114c1aae386d6 100644 (file)
--- a/test/MC/Mips/mips-expansions.s
+++ b/test/MC/Mips/mips-expansions.s
@@ -17,6 +17,22 @@
 # CHECK: lui     $7, 1               # encoding: [0x01,0x00,0x07,0x3c]
 # CHECK: ori     $7, $7, 2           # encoding: [0x02,0x00,0xe7,0x34]
 # CHECK: addu    $7, $7, $8          # encoding: [0x21,0x38,0xe8,0x00]
+# CHECK: lui     $8, %hi(symbol)     # encoding: [A,A,0x08,0x3c]
+                                     #   fixup A - offset: 0, value: symbol@ABS_HI, kind: fixup_Mips_HI16
+# CHECK: ori     $8, $8, %lo(symbol) # encoding: [A,A,0x08,0x35]
+                                     #   fixup A - offset: 0, value: symbol@ABS_LO, kind: fixup_Mips_LO16
+# CHECK: .set    mips64
+# CHECK: lui     $8, %highest(symbol)    # encoding: [A,A,0x08,0x3c]
+                                         #   fixup A - offset: 0, value: symbol@HIGHEST, kind: fixup_Mips_HIGHEST
+# CHECK: ori     $8, $8, %higher(symbol) # encoding: [A,A,0x08,0x35]
+                                         #   fixup A - offset: 0, value: symbol@HIGHER, kind: fixup_Mips_HIGHER
+# CHECK: dsll    $8, $8, 16              # encoding: [0x38,0x44,0x08,0x00]
+# CHECK: ori     $8, $8, %hi(symbol)     # encoding: [A,A,0x08,0x35]
+                                         #   fixup A - offset: 0, value: symbol@ABS_HI, kind: fixup_Mips_HI16
+# CHECK: dsll    $8, $8, 16              # encoding: [0x38,0x44,0x08,0x00]
+# CHECK: ori     $8, $8, %lo(symbol)     # encoding: [A,A,0x08,0x35]
+                                         #   fixup A - offset: 0, value: symbol@ABS_LO, kind: fixup_Mips_LO16
+# CHECK: .set    mips32r2
 # CHECK: lui     $10, %hi(symbol)        # encoding: [A,A,0x0a,0x3c]
 # CHECK:                                 #   fixup A - offset: 0, value: symbol@ABS_HI, kind: fixup_Mips_HI16
 # CHECK: addu    $10, $10, $4            # encoding: [0x21,0x50,0x44,0x01]
@@ -48,6 +64,10 @@
     la $7,65538
     la $a0, 20($a1)
     la $7,65538($8)
+    la $t0, symbol
+    .set mips64
+    la $t0, symbol
+    .set mips32r2
 
     .set noat
     lw  $t2, symbol($a0)