[SystemZ] Improve handling of inline asm constraints.

The "{=v0}" constraint did not result in the expected error message in the
abscence of the vector facility, because 'v0' matches as a string into the
AnyRegBitRegClass in common code.

This patch adds checks for vector support in case of "{v" and soft-float in
case of "{f" to remedy this.

Review: Ulrich Weigand.

Author: JonPsson

llvm/lib/Target/SystemZ/SystemZISelLowering.cpp

@@ -1163,7 +1163,10 @@ SystemZTargetLowering::getRegForInlineAsmConstraint(
       return parseRegisterNumber(Constraint, &SystemZ::GR64BitRegClass,
                                  SystemZMC::GR64Regs, 16);
     }
-    if (Constraint[1] == 'f' && !useSoftFloat()) {
+    if (Constraint[1] == 'f') {
+      if (useSoftFloat())
+        return std::make_pair(
+            0u, static_cast<const TargetRegisterClass *>(nullptr));
       if (VT == MVT::f32)
         return parseRegisterNumber(Constraint, &SystemZ::FP32BitRegClass,
                                    SystemZMC::FP32Regs, 16);
@@ -1174,6 +1177,9 @@ SystemZTargetLowering::getRegForInlineAsmConstraint(
                                  SystemZMC::FP64Regs, 16);
     }
     if (Constraint[1] == 'v') {
+      if (!Subtarget.hasVector())
+        return std::make_pair(
+            0u, static_cast<const TargetRegisterClass *>(nullptr));
       if (VT == MVT::f32)
         return parseRegisterNumber(Constraint, &SystemZ::VR32BitRegClass,
                                    SystemZMC::VR32Regs, 32);

llvm/test/CodeGen/SystemZ/soft-float-inline-asm-04.ll

@@ -0,0 +1,10 @@
+; RUN: not llc < %s -mtriple=s390x-linux-gnu -mcpu=z13 -mattr=soft-float -O3 2>&1 | FileCheck %s
+;
+; Verify that inline asms cannot use fp/vector registers with soft-float.
+
+define <2 x i64> @f1() {
+  %ret = call <2 x i64> asm "", "={v0}" ()
+  ret <2 x i64> %ret
+}
+
+; CHECK: error: couldn't allocate output register for constraint '{v0}'