AMDGPU: Fix crash if called function is a bitcast

getCalledFunction() is null, so this would crash. Replace
crash with an error on unsupported call.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243461 91177308-0d34-0410-b5e6-96231b3b80d8

test/CodeGen/AMDGPU/promote-alloca-bitcast-function.ll

@@ -0,0 +1,22 @@
+; RUN: not llc -march=amdgcn < %s 2>&1 | FileCheck %s
+
+; Make sure that AMDGPUPromoteAlloca doesn't crash if the called
+; function is a constantexpr cast of a function.
+
+declare void @foo(float*) #0
+declare void @foo.varargs(...) #0
+
+; CHECK: error: unsupported call to function foo in crash_call_constexpr_cast
+define void @crash_call_constexpr_cast() #0 {
+  %alloca = alloca i32
+  call void bitcast (void (float*)* @foo to void (i32*)*)(i32* %alloca) #0
+  ret void
+}
+
+define void @crash_call_constexpr_cast_varargs() #0 {
+  %alloca = alloca i32
+  call void bitcast (void (...)* @foo.varargs to void (i32*)*)(i32* %alloca) #0
+  ret void
+}
+
+attributes #0 = { nounwind }