DAG: Check libcall function is supported before emission

Whether the libcall implementation is supported should always
be checked before emission. Previously this would emit a call
to a non-existent function, and then since r600 doesn't support
calls it would error on the call. This switches it to a direct
legalization failure.

Also swap to use reportFatalInternalError. Probably should
be reportFatalUsageError; we don't want a backtrace and this will
never be fixed, but it is tested.

Author: arsenm

llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

@@ -178,10 +178,12 @@ TargetLowering::makeLibCall(SelectionDAG &DAG, RTLIB::Libcall LC, EVT RetVT,
     Args.push_back(Entry);
   }
 
-  if (LC == RTLIB::UNKNOWN_LIBCALL)
-    report_fatal_error("Unsupported library call operation!");
-  SDValue Callee = DAG.getExternalSymbol(getLibcallName(LC),
-                                         getPointerTy(DAG.getDataLayout()));
+  const char *LibcallName = getLibcallName(LC);
+  if (LC == RTLIB::UNKNOWN_LIBCALL || !LibcallName)
+    reportFatalInternalError("unsupported library call operation");
+
+  SDValue Callee =
+      DAG.getExternalSymbol(LibcallName, getPointerTy(DAG.getDataLayout()));
 
   Type *RetTy = RetVT.getTypeForEVT(*DAG.getContext());
   TargetLowering::CallLoweringInfo CLI(DAG);

llvm/test/CodeGen/AMDGPU/fneg.ll

@@ -3,7 +3,9 @@
 ; RUN: llc -mtriple=amdgcn -mcpu=tonga < %s | FileCheck -enable-var-scope -check-prefixes=GCN,VI %s
 ; RUN: llc -mtriple=amdgcn -mcpu=gfx1100 -mattr=+real-true16 < %s | FileCheck -enable-var-scope -check-prefixes=GCN,GFX11,GFX11-TRUE16 %s
 ; RUN: llc -mtriple=amdgcn -mcpu=gfx1100 -mattr=-real-true16 < %s | FileCheck -enable-var-scope -check-prefixes=GCN,GFX11,GFX11-FAKE16 %s
-; RUN: not llc -mtriple=r600 -mcpu=redwood < %s
+; RUN: not --crash llc -mtriple=r600 -mcpu=redwood < %s 2>&1 | FileCheck -check-prefix=R600-ERR %s
+
+; R600-ERR: LLVM ERROR: unsupported library call operation
 
 define amdgpu_kernel void @s_fneg_f32(ptr addrspace(1) %out, float %in) {
 ; SI-LABEL: s_fneg_f32: