Add support for ARM modified-immediate assembly syntax.

Certain ARM instructions accept 32-bit immediate operands encoded as a 8-bit
integer value (0-255) and a 4-bit rotation (0-30, even). Current ARM assembly
syntax support in LLVM allows the decoded (32-bit) immediate to be specified
as a single immediate operand for such instructions:

mov r0, #4278190080

The ARMARM defines an extended assembly syntax allowing the encoding to be made
more explicit, as in:

mov r0, #255, #8 ; (same 32-bit value as above)

The behaviour of the two instructions can be different w.r.t flags, which is
documented under "Modified immediate constants" in ARMARM. This patch enables
support for this extended syntax at the MC layer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223113 91177308-0d34-0410-b5e6-96231b3b80d8

Author: Asiri Rathnayake

lib/Target/ARM/ARMInstrInfo.td

@@ -587,6 +587,38 @@ def so_imm : Operand<i32>, ImmLeaf<i32, [{
   let DecoderMethod = "DecodeSOImmOperand";
 }
 
+// mod_imm: match a 32-bit immediate operand, which is encoded as a 12-bit
+// immediate (See ARMARM - "Modified Immediate Constants"). Unlike so_imm,
+// mod_imm keeps the immediate in its encoded form (within the MC layer).
+def ModImmAsmOperand: AsmOperandClass {
+  let Name = "ModImm";
+  let ParserMethod = "parseModImm";
+}
+def mod_imm : Operand<i32>, ImmLeaf<i32, [{
+    return ARM_AM::getSOImmVal(Imm) != -1;
+  }]> {
+  let EncoderMethod = "getModImmOpValue";
+  let PrintMethod = "printModImmOperand";
+  let ParserMatchClass = ModImmAsmOperand;
+}
+
+// similar to so_imm_not, but keeps the immediate in its encoded form
+def ModImmNotAsmOperand : AsmOperandClass { let Name = "ModImmNot"; }
+def mod_imm_not : Operand<i32>, PatLeaf<(imm), [{
+    return ARM_AM::getSOImmVal(~(uint32_t)N->getZExtValue()) != -1;
+  }], imm_not_XFORM> {
+  let ParserMatchClass = ModImmNotAsmOperand;
+}
+
+// similar to so_imm_neg, but keeps the immediate in its encoded form
+def ModImmNegAsmOperand : AsmOperandClass { let Name = "ModImmNeg"; }
+def mod_imm_neg : Operand<i32>, PatLeaf<(imm), [{
+    unsigned Value = -(unsigned)N->getZExtValue();
+    return Value && ARM_AM::getSOImmVal(Value) != -1;
+  }], imm_neg_XFORM> {
+  let ParserMatchClass = ModImmNegAsmOperand;
+}
+
 // Break so_imm's up into two pieces.  This handles immediates with up to 16
 // bits set in them.  This uses so_imm2part to match and so_imm2part_[12] to
 // get the first/second pieces.
@@ -1213,9 +1245,9 @@ multiclass AsI1_bin_irs<bits<4> opcod, string opc,
   // The register-immediate version is re-materializable. This is useful
   // in particular for taking the address of a local.
   let isReMaterializable = 1 in {
-  def ri : AsI1<opcod, (outs GPR:$Rd), (ins GPR:$Rn, so_imm:$imm), DPFrm,
+  def ri : AsI1<opcod, (outs GPR:$Rd), (ins GPR:$Rn, mod_imm:$imm), DPFrm,
                iii, opc, "\t$Rd, $Rn, $imm",
-               [(set GPR:$Rd, (opnode GPR:$Rn, so_imm:$imm))]>,
+               [(set GPR:$Rd, (opnode GPR:$Rn, mod_imm:$imm))]>,
            Sched<[WriteALU, ReadALU]> {
     bits<4> Rd;
     bits<4> Rn;
@@ -1286,9 +1318,9 @@ multiclass AsI1_rbin_irs<bits<4> opcod, string opc,
   // The register-immediate version is re-materializable. This is useful
   // in particular for taking the address of a local.
   let isReMaterializable = 1 in {
-  def ri : AsI1<opcod, (outs GPR:$Rd), (ins GPR:$Rn, so_imm:$imm), DPFrm,
+  def ri : AsI1<opcod, (outs GPR:$Rd), (ins GPR:$Rn, mod_imm:$imm), DPFrm,
                iii, opc, "\t$Rd, $Rn, $imm",
-               [(set GPR:$Rd, (opnode so_imm:$imm, GPR:$Rn))]>,
+               [(set GPR:$Rd, (opnode mod_imm:$imm, GPR:$Rn))]>,
            Sched<[WriteALU, ReadALU]> {
     bits<4> Rd;
     bits<4> Rn;
@@ -1356,9 +1388,9 @@ let hasPostISelHook = 1, Defs = [CPSR] in {
 multiclass AsI1_bin_s_irs<InstrItinClass iii, InstrItinClass iir,
                           InstrItinClass iis, PatFrag opnode,
                           bit Commutable = 0> {
-  def ri : ARMPseudoInst<(outs GPR:$Rd), (ins GPR:$Rn, so_imm:$imm, pred:$p),
+  def ri : ARMPseudoInst<(outs GPR:$Rd), (ins GPR:$Rn, mod_imm:$imm, pred:$p),
                          4, iii,
-                         [(set GPR:$Rd, CPSR, (opnode GPR:$Rn, so_imm:$imm))]>,
+                         [(set GPR:$Rd, CPSR, (opnode GPR:$Rn, mod_imm:$imm))]>,
                          Sched<[WriteALU, ReadALU]>;
 
   def rr : ARMPseudoInst<(outs GPR:$Rd), (ins GPR:$Rn, GPR:$Rm, pred:$p),
@@ -1389,9 +1421,9 @@ let hasPostISelHook = 1, Defs = [CPSR] in {
 multiclass AsI1_rbin_s_is<InstrItinClass iii, InstrItinClass iir,
                           InstrItinClass iis, PatFrag opnode,
                           bit Commutable = 0> {
-  def ri : ARMPseudoInst<(outs GPR:$Rd), (ins GPR:$Rn, so_imm:$imm, pred:$p),
+  def ri : ARMPseudoInst<(outs GPR:$Rd), (ins GPR:$Rn, mod_imm:$imm, pred:$p),
                          4, iii,
-                         [(set GPR:$Rd, CPSR, (opnode so_imm:$imm, GPR:$Rn))]>,
+                         [(set GPR:$Rd, CPSR, (opnode mod_imm:$imm, GPR:$Rn))]>,
            Sched<[WriteALU, ReadALU]>;
 
   def rsi : ARMPseudoInst<(outs GPR:$Rd),
@@ -1417,9 +1449,9 @@ let isCompare = 1, Defs = [CPSR] in {
 multiclass AI1_cmp_irs<bits<4> opcod, string opc,
                      InstrItinClass iii, InstrItinClass iir, InstrItinClass iis,
                        PatFrag opnode, bit Commutable = 0> {
-  def ri : AI1<opcod, (outs), (ins GPR:$Rn, so_imm:$imm), DPFrm, iii,
+  def ri : AI1<opcod, (outs), (ins GPR:$Rn, mod_imm:$imm), DPFrm, iii,
                opc, "\t$Rn, $imm",
-               [(opnode GPR:$Rn, so_imm:$imm)]>,
+               [(opnode GPR:$Rn, mod_imm:$imm)]>,
            Sched<[WriteCMP, ReadALU]> {
     bits<4> Rn;
     bits<12> imm;
@@ -1547,9 +1579,9 @@ let TwoOperandAliasConstraint = "$Rn = $Rd" in
 multiclass AI1_adde_sube_irs<bits<4> opcod, string opc, PatFrag opnode,
                              bit Commutable = 0> {
   let hasPostISelHook = 1, Defs = [CPSR], Uses = [CPSR] in {
-  def ri : AsI1<opcod, (outs GPR:$Rd), (ins GPR:$Rn, so_imm:$imm),
+  def ri : AsI1<opcod, (outs GPR:$Rd), (ins GPR:$Rn, mod_imm:$imm),
                 DPFrm, IIC_iALUi, opc, "\t$Rd, $Rn, $imm",
-               [(set GPR:$Rd, CPSR, (opnode GPR:$Rn, so_imm:$imm, CPSR))]>,
+               [(set GPR:$Rd, CPSR, (opnode GPR:$Rn, mod_imm:$imm, CPSR))]>,
                Requires<[IsARM]>,
            Sched<[WriteALU, ReadALU]> {
     bits<4> Rd;
@@ -1617,9 +1649,9 @@ multiclass AI1_adde_sube_irs<bits<4> opcod, string opc, PatFrag opnode,
 let TwoOperandAliasConstraint = "$Rn = $Rd" in
 multiclass AI1_rsc_irs<bits<4> opcod, string opc, PatFrag opnode> {
   let hasPostISelHook = 1, Defs = [CPSR], Uses = [CPSR] in {
-  def ri : AsI1<opcod, (outs GPR:$Rd), (ins GPR:$Rn, so_imm:$imm),
+  def ri : AsI1<opcod, (outs GPR:$Rd), (ins GPR:$Rn, mod_imm:$imm),
                 DPFrm, IIC_iALUi, opc, "\t$Rd, $Rn, $imm",
-               [(set GPR:$Rd, CPSR, (opnode so_imm:$imm, GPR:$Rn, CPSR))]>,
+               [(set GPR:$Rd, CPSR, (opnode mod_imm:$imm, GPR:$Rn, CPSR))]>,
                Requires<[IsARM]>,
            Sched<[WriteALU, ReadALU]> {
     bits<4> Rd;
@@ -3224,8 +3256,8 @@ def MOVsi : AsI1<0b1101, (outs GPR:$Rd), (ins shift_so_reg_imm:$src),
 }
 
 let isReMaterializable = 1, isAsCheapAsAMove = 1, isMoveImm = 1 in
-def MOVi : AsI1<0b1101, (outs GPR:$Rd), (ins so_imm:$imm), DPFrm, IIC_iMOVi,
-                "mov", "\t$Rd, $imm", [(set GPR:$Rd, so_imm:$imm)]>, UnaryDP,
+def MOVi : AsI1<0b1101, (outs GPR:$Rd), (ins mod_imm:$imm), DPFrm, IIC_iMOVi,
+                "mov", "\t$Rd, $imm", [(set GPR:$Rd, mod_imm:$imm)]>, UnaryDP,
                 Sched<[WriteALU]> {
   bits<4> Rd;
   bits<12> imm;
@@ -3732,9 +3764,9 @@ def  MVNsr  : AsI1<0b1111, (outs GPR:$Rd), (ins so_reg_reg:$shift),
   let Inst{3-0} = shift{3-0};
 }
 let isReMaterializable = 1, isAsCheapAsAMove = 1, isMoveImm = 1 in
-def  MVNi  : AsI1<0b1111, (outs GPR:$Rd), (ins so_imm:$imm), DPFrm,
+def  MVNi  : AsI1<0b1111, (outs GPR:$Rd), (ins mod_imm:$imm), DPFrm,
                   IIC_iMVNi, "mvn", "\t$Rd, $imm",
-                  [(set GPR:$Rd, so_imm_not:$imm)]>,UnaryDP, Sched<[WriteALU]> {
+                  [(set GPR:$Rd, mod_imm_not:$imm)]>,UnaryDP, Sched<[WriteALU]> {
   bits<4> Rd;
   bits<12> imm;
   let Inst{25} = 1;
@@ -4280,9 +4312,9 @@ def : ARMPat<(ARMcmpZ GPR:$src, so_reg_reg:$rhs),
 
 // CMN register-integer
 let isCompare = 1, Defs = [CPSR] in {
-def CMNri : AI1<0b1011, (outs), (ins GPR:$Rn, so_imm:$imm), DPFrm, IIC_iCMPi,
+def CMNri : AI1<0b1011, (outs), (ins GPR:$Rn, mod_imm:$imm), DPFrm, IIC_iCMPi,
                 "cmn", "\t$Rn, $imm",
-                [(ARMcmn GPR:$Rn, so_imm:$imm)]>,
+                [(ARMcmn GPR:$Rn, mod_imm:$imm)]>,
                 Sched<[WriteCMP, ReadALU]> {
   bits<4> Rn;
   bits<12> imm;
@@ -5130,17 +5162,17 @@ def MSR : ABI<0b0001, (outs), (ins msr_mask:$mask, GPR:$Rn), NoItinerary,
   let Inst{3-0} = Rn;
 }
 
-def MSRi : ABI<0b0011, (outs), (ins msr_mask:$mask,  so_imm:$a), NoItinerary,
-               "msr", "\t$mask, $a", []> {
+def MSRi : ABI<0b0011, (outs), (ins msr_mask:$mask,  mod_imm:$imm), NoItinerary,
+               "msr", "\t$mask, $imm", []> {
   bits<5> mask;
-  bits<12> a;
+  bits<12> imm;
 
   let Inst{23} = 0;
   let Inst{22} = mask{4}; // R bit
   let Inst{21-20} = 0b10;
   let Inst{19-16} = mask{3-0};
   let Inst{15-12} = 0b1111;
-  let Inst{11-0} = a;
+  let Inst{11-0} = imm;
 }
 
 // However, the MSR (banked register) system instruction (ARMv7VE) *does* have a
@@ -5549,33 +5581,33 @@ def : MnemonicAlias<"usubaddx", "usax">;
 // "mov Rd, so_imm_not" can be handled via "mvn" in assembly, just like
 // for isel.
 def : ARMInstAlias<"mov${s}${p} $Rd, $imm",
-                   (MVNi rGPR:$Rd, so_imm_not:$imm, pred:$p, cc_out:$s)>;
+                   (MVNi rGPR:$Rd, mod_imm_not:$imm, pred:$p, cc_out:$s)>;
 def : ARMInstAlias<"mvn${s}${p} $Rd, $imm",
-                   (MOVi rGPR:$Rd, so_imm_not:$imm, pred:$p, cc_out:$s)>;
+                   (MOVi rGPR:$Rd, mod_imm_not:$imm, pred:$p, cc_out:$s)>;
 // Same for AND <--> BIC
 def : ARMInstAlias<"bic${s}${p} $Rd, $Rn, $imm",
-                   (ANDri rGPR:$Rd, rGPR:$Rn, so_imm_not:$imm,
+                   (ANDri rGPR:$Rd, rGPR:$Rn, mod_imm_not:$imm,
                           pred:$p, cc_out:$s)>;
 def : ARMInstAlias<"bic${s}${p} $Rdn, $imm",
-                   (ANDri rGPR:$Rdn, rGPR:$Rdn, so_imm_not:$imm,
+                   (ANDri rGPR:$Rdn, rGPR:$Rdn, mod_imm_not:$imm,
                           pred:$p, cc_out:$s)>;
 def : ARMInstAlias<"and${s}${p} $Rd, $Rn, $imm",
-                   (BICri rGPR:$Rd, rGPR:$Rn, so_imm_not:$imm,
+                   (BICri rGPR:$Rd, rGPR:$Rn, mod_imm_not:$imm,
                           pred:$p, cc_out:$s)>;
 def : ARMInstAlias<"and${s}${p} $Rdn, $imm",
-                   (BICri rGPR:$Rdn, rGPR:$Rdn, so_imm_not:$imm,
+                   (BICri rGPR:$Rdn, rGPR:$Rdn, mod_imm_not:$imm,
                           pred:$p, cc_out:$s)>;
 
 // Likewise, "add Rd, so_imm_neg" -> sub
 def : ARMInstAlias<"add${s}${p} $Rd, $Rn, $imm",
-                 (SUBri GPR:$Rd, GPR:$Rn, so_imm_neg:$imm, pred:$p, cc_out:$s)>;
+                 (SUBri GPR:$Rd, GPR:$Rn, mod_imm_neg:$imm, pred:$p, cc_out:$s)>;
 def : ARMInstAlias<"add${s}${p} $Rd, $imm",
-                 (SUBri GPR:$Rd, GPR:$Rd, so_imm_neg:$imm, pred:$p, cc_out:$s)>;
+                 (SUBri GPR:$Rd, GPR:$Rd, mod_imm_neg:$imm, pred:$p, cc_out:$s)>;
 // Same for CMP <--> CMN via so_imm_neg
 def : ARMInstAlias<"cmp${p} $Rd, $imm",
-                   (CMNri rGPR:$Rd, so_imm_neg:$imm, pred:$p)>;
+                   (CMNri rGPR:$Rd, mod_imm_neg:$imm, pred:$p)>;
 def : ARMInstAlias<"cmn${p} $Rd, $imm",
-                   (CMPri rGPR:$Rd, so_imm_neg:$imm, pred:$p)>;
+                   (CMPri rGPR:$Rd, mod_imm_neg:$imm, pred:$p)>;
 
 // The shifter forms of the MOV instruction are aliased to the ASR, LSL,
 // LSR, ROR, and RRX instructions.

lib/Target/ARM/ARMMCInstLower.cpp

@@ -119,11 +119,45 @@ void llvm::LowerARMMachineInstrToMCInst(const MachineInstr *MI, MCInst &OutMI,
                                         ARMAsmPrinter &AP) {
   OutMI.setOpcode(MI->getOpcode());
 
+  // In the MC layer, we keep modified immediates in their encoded form
+  bool EncodeImms = false;
+  switch (MI->getOpcode()) {
+  default: break;
+  case ARM::MOVi:
+  case ARM::MVNi:
+  case ARM::CMPri:
+  case ARM::CMNri:
+  case ARM::TSTri:
+  case ARM::TEQri:
+  case ARM::MSRi:
+  case ARM::ADCri:
+  case ARM::ADDri:
+  case ARM::ADDSri:
+  case ARM::SBCri:
+  case ARM::SUBri:
+  case ARM::SUBSri:
+  case ARM::ANDri:
+  case ARM::ORRri:
+  case ARM::EORri:
+  case ARM::BICri:
+  case ARM::RSBri:
+  case ARM::RSBSri:
+  case ARM::RSCri:
+    EncodeImms = true;
+    break;
+  }
+
   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
     const MachineOperand &MO = MI->getOperand(i);
 
     MCOperand MCOp;
-    if (AP.lowerOperand(MO, MCOp))
+    if (AP.lowerOperand(MO, MCOp)) {
+      if (MCOp.isImm() && EncodeImms) {
+        int32_t Enc = ARM_AM::getSOImmVal(MCOp.getImm());
+        if (Enc != -1)
+          MCOp.setImm(Enc);
+      }
       OutMI.addOperand(MCOp);
+    }
   }
 }