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

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])
+  if (ExtraCode && ExtraCode[0]) {
-    return true; // Unknown modifier.
+    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);

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;
 }

test/CodeGen/PowerPC/asm-Zy.ll

@@ -0,0 +1,14 @@
+target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
+target triple = "powerpc64-bgq-linux"
+; RUN: llc < %s -march=ppc64 -mcpu=a2 | FileCheck %s
+
+define i32 @zytest(i32 %a) nounwind {
+entry:
+; CHECK: @zytest
+  %r = call i32 asm "lwbrx $0, ${1:y}", "=r,Z"(i32 %a) nounwind, !srcloc !0
+  ret i32 %r
+; CHECK: lwbrx 3, 0,
+}
+
+!0 = metadata !{i32 101688}
+