[AVR] Fix broken bitcast for aliases in non-zero address space

[aykevl]

Summary

This was triggered by some code in picolibc. The minimal version looks like this:

double infinity(void) {
   return 5;
}

extern long double infinityl() __attribute__((__alias__("infinity")));

These two declarations have a different type (not because of the 'long double', which is also 'double' in IR, but because infinityl has no (void) and is therefore a variadic function). This led to a crash in the bitcast which assumed address space 0.

[aykevl]

• add CHECK: line that I forgot

[aykevl]

• now _actually_ add that CHECK line

[arichardson]

LGTM

clang/lib/CodeGen/CodeGenModule.cpp

if ((isa<llvm::Function>(Entry) || isa<llvm::GlobalAlias>(Entry)) &&
         (Entry->getValueType() == Ty)) {
       return Entry;
     }
 
     // Make sure the result is of the correct type.
     // (If function is requested for a definition, we always need to create a new
     // function, not just return a bitcast.)
     if (!IsForDefinition)
-      return llvm::ConstantExpr::getBitCast(Entry, Ty->getPointerTo());
+      return llvm::ConstantExpr::getBitCast(
+          Entry, Ty->getPointerTo(Entry->getAddressSpace()));
   }
 
   // This function doesn't have a complete type (for example, the return
   // type is an incomplete struct). Use a fake type instead, and make
   // sure not to try to set attributes.
   bool IsIncompleteFunction = false;
 
   llvm::FunctionType *FTy;

clang/test/CodeGen/avr/alias-avr.c

 // RUN: %clang_cc1 -triple avr-unknown-unknown -emit-llvm -o - %s | FileCheck %s
 
 int mul(int a, int b) {
   return a * b;
 }
 
 // CHECK: @multiply ={{.*}} alias i16 (i16, i16), ptr addrspace(1) @mul
 int multiply(int x, int y) __attribute__((alias("mul")));
+
+// Make sure the correct address space is used when creating an alias that needs
+// a pointer cast.
+// CHECK: @smallmul = alias i8 (i16, i16), ptr addrspace(1) @mul
+char smallmul(int a, int b) __attribute__((alias("mul")));