[GlobalISel] Introduce a G_FSQRT generic instruction

This introduces a generic instruction for computing the floating point
square root of a value.

Right now, we can't select @llvm.sqrt, so this is working towards fixing that.

llvm-svn: 352668

llvm/include/llvm/Support/TargetOpcodes.def

@@ -526,6 +526,9 @@ HANDLE_TARGET_OPCODE(G_FCOS)
 /// Floating point sine.
 HANDLE_TARGET_OPCODE(G_FSIN)
 
+/// Floating point square root.
+HANDLE_TARGET_OPCODE(G_FSQRT)
+
 /// Generic AddressSpaceCast.
 HANDLE_TARGET_OPCODE(G_ADDRSPACE_CAST)
 

llvm/include/llvm/Target/GenericOpcodes.td

@@ -569,6 +569,16 @@ def G_FSIN : GenericInstruction {
   let hasSideEffects = 0;
 }
 
+// Floating point square root of a value.
+// This returns NaN for negative nonzero values.
+// NOTE: Unlike libm sqrt(), this never sets errno. In all other respects it's
+// libm-conformant.
+def G_FSQRT : GenericInstruction {
+  let OutOperandList = (outs type0:$dst);
+  let InOperandList = (ins type0:$src1);
+  let hasSideEffects = 0;
+}
+
 //------------------------------------------------------------------------------
 // Opcodes for LLVM Intrinsics
 //------------------------------------------------------------------------------

llvm/include/llvm/Target/GlobalISel/SelectionDAGCompat.td

@@ -91,6 +91,7 @@ def : GINodeEquiv<G_EXTRACT_VECTOR_ELT, vector_extract>;
 def : GINodeEquiv<G_FCEIL, fceil>;
 def : GINodeEquiv<G_FCOS, fcos>;
 def : GINodeEquiv<G_FSIN, fsin>;
+def : GINodeEquiv<G_FSQRT, fsqrt>;
 
 // Broadly speaking G_LOAD is equivalent to ISD::LOAD but there are some
 // complications that tablegen must take care of. For example, Predicates such

llvm/test/CodeGen/AArch64/GlobalISel/legalizer-info-validation.mir

@@ -338,6 +338,9 @@
 #
 # DEBUG-NEXT: G_FSIN (opcode {{[0-9]+}}): 1 type index
 # DEBUG: .. the first uncovered type index: 1, OK
+#
+# DEBUG-NEXT: G_FSQRT (opcode {{[0-9]+}}): 1 type index
+# DEBUG: .. the first uncovered type index: 1, OK
 
 # CHECK-NOT: ill-defined