3 files changed, 54 insertions, 11 deletions
diff --git a/lib/Target/ARM/ARMInstrThumb2.td b/lib/Target/ARM/ARMInstrThumb2.td
index 2b94422..3b73c1f 100644
--- a/lib/Target/ARM/ARMInstrThumb2.td
+++ b/lib/Target/ARM/ARMInstrThumb2.td
@@ -3683,13 +3683,13 @@ def t2MSR_AR : T2I<(outs), (ins msr_mask:$mask, rGPR:$Rn),
 def t2MSR_M : T2I<(outs), (ins msr_mask:$SYSm, rGPR:$Rn),
                   NoItinerary, "msr", "\t$SYSm, $Rn", []>,
               Requires<[IsThumb,IsMClass]> {
-  bits<8> SYSm;
+  bits<12> SYSm;
   bits<4> Rn;
   let Inst{31-21} = 0b11110011100;
   let Inst{20}    = 0b0;
   let Inst{19-16} = Rn;
   let Inst{15-12} = 0b1000;
-  let Inst{7-0}  = SYSm;
+  let Inst{11-0}  = SYSm;
 }
 
 
diff --git a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 8865979..00e7f6e 100644
--- a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -3324,10 +3324,35 @@ parseMSRMaskOperand(SmallVectorImpl<MCParsedAsmOperand*> &Operands) {
     // See ARMv6-M 10.1.1
     std::string Name = Mask.lower();
     unsigned FlagsVal = StringSwitch<unsigned>(Name)
-      .Case("apsr", 0)
-      .Case("iapsr", 1)
-      .Case("eapsr", 2)
-      .Case("xpsr", 3)
+      // Note: in the documentation:
+      //  ARM deprecates using MSR APSR without a _<bits> qualifier as an alias
+      //  for MSR APSR_nzcvq.
+      // but we do make it an alias here.  This is so to get the "mask encoding"
+      // bits correct on MSR APSR writes.
+      //
+      // FIXME: Note the 0xc00 "mask encoding" bits version of the registers
+      // should really only be allowed when writing a special register.  Note
+      // they get dropped in the MRS instruction reading a special register as
+      // the SYSm field is only 8 bits.
+      //
+      // FIXME: the _g and _nzcvqg versions are only allowed if the processor
+      // includes the DSP extension but that is not checked.
+      .Case("apsr", 0x800)
+      .Case("apsr_nzcvq", 0x800)
+      .Case("apsr_g", 0x400)
+      .Case("apsr_nzcvqg", 0xc00)
+      .Case("iapsr", 0x801)
+      .Case("iapsr_nzcvq", 0x801)
+      .Case("iapsr_g", 0x401)
+      .Case("iapsr_nzcvqg", 0xc01)
+      .Case("eapsr", 0x802)
+      .Case("eapsr_nzcvq", 0x802)
+      .Case("eapsr_g", 0x402)
+      .Case("eapsr_nzcvqg", 0xc02)
+      .Case("xpsr", 0x803)
+      .Case("xpsr_nzcvq", 0x803)
+      .Case("xpsr_g", 0x403)
+      .Case("xpsr_nzcvqg", 0xc03)
       .Case("ipsr", 5)
       .Case("epsr", 6)
       .Case("iepsr", 7)
diff --git a/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp b/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
index be7e098..70e4317 100644
--- a/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
+++ b/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
@@ -647,12 +647,30 @@ void ARMInstPrinter::printMSRMaskOperand(const MCInst *MI, unsigned OpNum,
   unsigned Mask = Op.getImm() & 0xf;
 
   if (getAvailableFeatures() & ARM::FeatureMClass) {
-    switch (Op.getImm()) {
+    unsigned SYSm = Op.getImm();
+    unsigned Opcode = MI->getOpcode();
+    // For reads of the special registers ignore the "mask encoding" bits
+    // which are only for writes.
+    if (Opcode == ARM::t2MRS_M)
+      SYSm &= 0xff;
+    switch (SYSm) {
     default: llvm_unreachable("Unexpected mask value!");
-    case 0: O << "apsr"; return;
-    case 1: O << "iapsr"; return;
-    case 2: O << "eapsr"; return;
-    case 3: O << "xpsr"; return;
+    case     0:
+    case 0x800: O << "apsr"; return; // with _nzcvq bits is an alias for aspr
+    case 0x400: O << "apsr_g"; return;
+    case 0xc00: O << "apsr_nzcvqg"; return;
+    case     1:
+    case 0x801: O << "iapsr"; return; // with _nzcvq bits is an alias for iapsr
+    case 0x401: O << "iapsr_g"; return;
+    case 0xc01: O << "iapsr_nzcvqg"; return;
+    case     2:
+    case 0x802: O << "eapsr"; return; // with _nzcvq bits is an alias for eapsr
+    case 0x402: O << "eapsr_g"; return;
+    case 0xc02: O << "eapsr_nzcvqg"; return;
+    case     3:
+    case 0x803: O << "xpsr"; return; // with _nzcvq bits is an alias for xpsr
+    case 0x403: O << "xpsr_g"; return;
+    case 0xc03: O << "xpsr_nzcvqg"; return;
     case 5: O << "ipsr"; return;
     case 6: O << "epsr"; return;
     case 7: O << "iepsr"; return;