Add support for the PowerPC-specific inline asm Z constraint and y modifier.

The Z constraint specifies an r+r memory address, and the y modifier expands
to the "r, r" in the asm string. For this initial implementation, the base
register is forced to r0 (which has the special meaning of 0 for r+r addressing
on PowerPC) and the full address is taken in the second register. In the
future, this should be improved.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167388 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 27 insertions, 2 deletions

diff --git a/lib/Target/PowerPC/PPCAsmPrinter.cpp b/lib/Target/PowerPC/PPCAsmPrinter.cpp
index 72395bb283..4387730fcc 100644
--- a/lib/Target/PowerPC/PPCAsmPrinter.cpp
+++ b/lib/Target/PowerPC/PPCAsmPrinter.cpp
@@ -284,8 +284,22 @@ bool PPCAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
                                           unsigned AsmVariant,
                                           const char *ExtraCode,
                                           raw_ostream &O) {
-  if (ExtraCode && ExtraCode[0])
-    return true; // Unknown modifier.
+  if (ExtraCode && ExtraCode[0]) {
+    if (ExtraCode[1] != 0) return true; // Unknown modifier.
+
+    switch (ExtraCode[0]) {
+    default: return true;  // Unknown modifier.
+    case 'y': // A memory reference for an X-form instruction
+      {
+        const char *RegName = "r0";
+        if (!Subtarget.isDarwin()) RegName = stripRegisterPrefix(RegName);
+        O << RegName << ", ";
+        printOperand(MI, OpNo, O);
+        return false;
+      }
+    }
+  }
+
   assert(MI->getOperand(OpNo).isReg());
   O << "0(";
   printOperand(MI, OpNo, O);
diff --git a/lib/Target/PowerPC/PPCISelLowering.cpp b/lib/Target/PowerPC/PPCISelLowering.cpp
index 0922011d97..cda7e8cdc1 100644
--- a/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -6443,6 +6443,14 @@ PPCTargetLowering::getConstraintType(const std::string &Constraint) const {
     case 'v':
     case 'y':
       return C_RegisterClass;
+    case 'Z':
+      // FIXME: While Z does indicate a memory constraint, it specifically
+      // indicates an r+r address (used in conjunction with the 'y' modifier
+      // in the replacement string). Currently, we're forcing the base
+      // register to be r0 in the asm printer (which is interpreted as zero)
+      // and forming the complete address in the second register. This is
+      // suboptimal.
+      return C_Memory;
     }
   }
   return TargetLowering::getConstraintType(Constraint);
@@ -6485,6 +6493,9 @@ PPCTargetLowering::getSingleConstraintMatchWeight(
   case 'y':
     weight = CW_Register;
     break;
+  case 'Z':
+    weight = CW_Memory;
+    break;
   }
   return weight;
 }