[PATCH] [X86] Support 'V' register operand modifier

[David Woodhouse via llvm-commits]

This allows the register name to be printed without the leading '%'.
This can be used for emitting calls to the retpoline thunks from inline
asm.
---
 lib/Target/X86/X86AsmPrinter.cpp          | 11 ++++++++++-
 test/CodeGen/X86/inline-asm-modifier-V.ll | 14 ++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 test/CodeGen/X86/inline-asm-modifier-V.ll

diff --git a/lib/Target/X86/X86AsmPrinter.cpp b/lib/Target/X86/X86AsmPrinter.cpp
index 4da7d59df46..991a81c8f11 100644
--- a/lib/Target/X86/X86AsmPrinter.cpp
+++ b/lib/Target/X86/X86AsmPrinter.cpp
@@ -370,6 +370,8 @@ static void printIntelMemReference(X86AsmPrinter &P, const MachineInstr *MI,
 static bool printAsmMRegister(X86AsmPrinter &P, const MachineOperand &MO,
                               char Mode, raw_ostream &O) {
   unsigned Reg = MO.getReg();
+  bool EmitPercent = true;
+
   switch (Mode) {
   default: return true;  // Unknown mode.
   case 'b': // Print QImode register
@@ -384,6 +386,9 @@ static bool printAsmMRegister(X86AsmPrinter &P, const MachineOperand &MO,
   case 'k': // Print SImode register
     Reg = getX86SubSuperRegister(Reg, 32);
     break;
+  case 'V':
+    EmitPercent = false;
+    LLVM_FALLTHROUGH;
   case 'q':
     // Print 64-bit register names if 64-bit integer registers are available.
     // Otherwise, print 32-bit register names.
@@ -391,7 +396,10 @@ static bool printAsmMRegister(X86AsmPrinter &P, const MachineOperand &MO,
     break;
   }
 
-  O << '%' << X86ATTInstPrinter::getRegisterName(Reg);
+  if (EmitPercent)
+    O << '%';
+
+  O << X86ATTInstPrinter::getRegisterName(Reg);
   return false;
 }
 
@@ -464,6 +472,7 @@ bool X86AsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
     case 'w': // Print HImode register
     case 'k': // Print SImode register
     case 'q': // Print DImode register
+    case 'V': // Print native register without '%'
       if (MO.isReg())
         return printAsmMRegister(*this, MO, ExtraCode[0], O);
       printOperand(*this, MI, OpNo, O);
diff --git a/test/CodeGen/X86/inline-asm-modifier-V.ll b/test/CodeGen/X86/inline-asm-modifier-V.ll
new file mode 100644
index 00000000000..3e76b4e4b9f
--- /dev/null
+++ b/test/CodeGen/X86/inline-asm-modifier-V.ll
@@ -0,0 +1,14 @@
+; RUN: llc < %s -mtriple=i686-- -no-integrated-as | FileCheck -check-prefix=X86 %s
+; RUN: llc < %s -mtriple=x86_64-- -no-integrated-as | FileCheck -check-prefix=X64 %s
+
+; If the target does not have 64-bit integer registers, emit 32-bit register
+; names.
+
+; X86: calll __x86_indirect_thunk_e{{[abcd]}}x
+; X64: callq __x86_indirect_thunk_r
+
+define void @q_modifier(i32* %p) {
+entry:
+  tail call void asm sideeffect "call __x86_indirect_thunk_${0:V}", "r,~{dirflag},~{fpsr},~{flags}"(i32* %p)
+  ret void
+}
-- 
2.14.3