AMDGPU: Fix crash if called function is a bitcast

[arsenm]

Summary

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

[• tstellarAMD]

LGTM.

[arsenm]

r243461

lib/Target/AMDGPU/AMDGPUPromoteAlloca.cpp

static bool tryPromoteAllocaToVector(AllocaInst *Alloca) {
   return true;
 }
 
 static bool collectUsesWithPtrTypes(Value *Val, std::vector<Value*> &WorkList) {
   bool Success = true;
   for (User *User : Val->users()) {
     if(std::find(WorkList.begin(), WorkList.end(), User) != WorkList.end())
       continue;
-    if (isa<CallInst>(User)) {
+    if (CallInst *CI = dyn_cast<CallInst>(User)) {
+      // TODO: We might be able to handle some cases where the callee is a
+      // constantexpr bitcast of a function.
+      if (!CI->getCalledFunction())
+        return false;
+
       WorkList.push_back(User);
       continue;
     }
 
     // FIXME: Correctly handle ptrtoint instructions.
     Instruction *UseInst = dyn_cast<Instruction>(User);
     if (UseInst && UseInst->getOpcode() == Instruction::PtrToInt)
       return false;

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

+; 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 }