Tweak ARM assembly parsing and printing of MSR instruction.

The system register spec should be case insensitive. The preferred form for
output with mask values of 4, 8, and 12 references APSR rather than CPSR.
Update and tidy up tests accordingly.

llvm-svn: 135532

3 files changed, 19 insertions, 8 deletions

diff --git a/llvm/lib/Target/ARM/ARMInstrInfo.td b/llvm/lib/Target/ARM/ARMInstrInfo.td
index 23a7c1bfcbf..9a140679a7b 100644
--- a/llvm/lib/Target/ARM/ARMInstrInfo.td
+++ b/llvm/lib/Target/ARM/ARMInstrInfo.td
@@ -3798,8 +3798,7 @@ def MRSsys : ABI<0b0001, (outs GPR:$Rd), (ins), NoItinerary,
 // operand contains the special register (R Bit) in bit 4 and bits 3-0 contains
 // the mask with the fields to be accessed in the special register.
 def MSR : ABI<0b0001, (outs), (ins msr_mask:$mask, GPR:$Rn), NoItinerary,
-              "msr", "\t$mask, $Rn",
-              [/* For disassembly only; pattern left blank */]> {
+              "msr", "\t$mask, $Rn", []> {
   bits<5> mask;
   bits<4> Rn;
 
@@ -3813,8 +3812,7 @@ def MSR : ABI<0b0001, (outs), (ins msr_mask:$mask, GPR:$Rn), NoItinerary,
 }
 
 def MSRi : ABI<0b0011, (outs), (ins msr_mask:$mask,  so_imm:$a), NoItinerary,
-               "msr", "\t$mask, $a",
-               [/* For disassembly only; pattern left blank */]> {
+               "msr", "\t$mask, $a", []> {
   bits<5> mask;
   bits<12> a;
 
diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 752e90af775..0cf9a4a042e 100644
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -1430,7 +1430,7 @@ tryParseMSRMaskOperand(SmallVectorImpl<MCParsedAsmOperand*> &Operands) {
   // Split spec_reg from flag, example: CPSR_sxf => "CPSR" and "sxf"
   size_t Start = 0, Next = Mask.find('_');
   StringRef Flags = "";
-  StringRef SpecReg = Mask.slice(Start, Next);
+  std::string SpecReg = LowercaseString(Mask.slice(Start, Next));
   if (Next != StringRef::npos)
     Flags = Mask.slice(Next+1, Mask.size());
 
@@ -1441,7 +1441,7 @@ tryParseMSRMaskOperand(SmallVectorImpl<MCParsedAsmOperand*> &Operands) {
 
   if (SpecReg == "apsr") {
     FlagsVal = StringSwitch<unsigned>(Flags)
-    .Case("nzcvq",  0x8) // same as CPSR_c
+    .Case("nzcvq",  0x8) // same as CPSR_f
     .Case("g",      0x4) // same as CPSR_s
     .Case("nzcvqg", 0xc) // same as CPSR_fs
     .Default(~0U);
diff --git a/llvm/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp b/llvm/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
index c90fe66f262..4a178dc9215 100644
--- a/llvm/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
+++ b/llvm/lib/Target/ARM/InstPrinter/ARMInstPrinter.cpp
@@ -481,10 +481,23 @@ void ARMInstPrinter::printMSRMaskOperand(const MCInst *MI, unsigned OpNum,
   unsigned SpecRegRBit = Op.getImm() >> 4;
   unsigned Mask = Op.getImm() & 0xf;
 
+  // As special cases, CPSR_f, CPSR_s and CPSR_fs prefer printing as
+  // APSR_nzcvq, APSR_g and APSRnzcvqg, respectively.
+  if (!SpecRegRBit && (Mask == 8 || Mask == 4 || Mask == 12)) {
+    O << "APSR_";
+    switch (Mask) {
+    default: assert(0);
+    case 4:  O << "g"; return;
+    case 8:  O << "nzcvq"; return;
+    case 12: O << "nzcvqg"; return;
+    }
+    llvm_unreachable("Unexpected mask value!");
+  }
+
   if (SpecRegRBit)
-    O << "spsr";
+    O << "SPSR";
   else
-    O << "cpsr";
+    O << "CPSR";
 
   if (Mask) {
     O << '_';