AMDGPU: Don't error on out of bounds address spaces

[arsenm]

Summary

We should never abort on valid IR. The most reasonable
interpretation of an arbitrary address space pointer is
probably some kind of special subset of global memory.

[rampitec]

LGTM.
A note though, I would think of it as a some subset of flat.

[arsenm]

r341894

lib/Target/AMDGPU/AMDGPUAliasAnalysis.cpp

static const AliasResult ASAliasRules[7][7] = {
     /* Group    */        {MayAlias, NoAlias , NoAlias , MayAlias, NoAlias , NoAlias , NoAlias},
     /* Constant */        {MayAlias, MayAlias, MayAlias, NoAlias , NoAlias,  NoAlias , MayAlias},
     /* Private  */        {MayAlias, NoAlias , NoAlias , NoAlias , NoAlias , MayAlias, NoAlias},
     /* Constant 32-bit */ {MayAlias, MayAlias, MayAlias, NoAlias , MayAlias, NoAlias , NoAlias}
   };
 
   static_assert(AMDGPUAS::MAX_AMDGPU_ADDRESS <= 6, "Addr space out of range");
 
-
-  if (AS1 > AMDGPUAS::MAX_AMDGPU_ADDRESS || AS2 > AMDGPUAS::MAX_AMDGPU_ADDRESS) {
-    if (Arch == Triple::amdgcn)
-      report_fatal_error("Pointer address space out of range");
-    return AS1 == AS2 ? MayAlias : NoAlias;
-  }
+  if (AS1 > AMDGPUAS::MAX_AMDGPU_ADDRESS || AS2 > AMDGPUAS::MAX_AMDGPU_ADDRESS)
+    return MayAlias;
 
   return ASAliasRules[AS1][AS2];
 }
 
 AliasResult AMDGPUAAResult::alias(const MemoryLocation &LocA,
                                   const MemoryLocation &LocB) {
   unsigned asA = LocA.Ptr->getType()->getPointerAddressSpace();
   unsigned asB = LocB.Ptr->getType()->getPointerAddressSpace();

test/CodeGen/AMDGPU/amdgpu-alias-analysis.ll

 }
 
 ; CHECK: MayAlias:      i8 addrspace(4)* %p1, i8 addrspace(6)* %p
 
 define void @test_constant_32bit_vs_constant(i8 addrspace(6)* %p, i8 addrspace(4)* %p1) {
   ret void
 }
 
+; CHECK: MayAlias:  i8 addrspace(999)* %p0, i8* %p
+define void @test_0_999(i8 addrspace(0)* %p, i8 addrspace(999)* %p0) {
+  ret void
+}
+
+; CHECK: MayAlias:  i8 addrspace(999)* %p, i8* %p1
+define void @test_999_0(i8 addrspace(999)* %p, i8 addrspace(0)* %p1) {
+  ret void
+}
+
+; CHECK: MayAlias:  i8 addrspace(1)* %p, i8 addrspace(999)* %p1
+define void @test_1_999(i8 addrspace(1)* %p, i8 addrspace(999)* %p1) {
+  ret void
+}
+
+; CHECK: MayAlias:  i8 addrspace(1)* %p1, i8 addrspace(999)* %p
+define void @test_999_1(i8 addrspace(999)* %p, i8 addrspace(1)* %p1) {
+  ret void
+}