IR: Make getRetAlign check callee function attributes

[arsenm]

Summary

The attribute queries semi-consistently check the attribute set, and
then fallback to checking the callee's attributes.

[jdoerfert]

Still inconsistent after but I guess somewhat better.

[arsenm]

3d2d208f6a0a421b23937c39b9d371183a5913a3

llvm/include/llvm/IR/InstrTypes.h

public:
   // FIXME: Once this API is no longer duplicated in `CallSite`, rename this to
   // better indicate that this may return a conservative answer.
   bool doesNotReadMemory(unsigned OpNo) const {
     return dataOperandHasImpliedAttr(OpNo, Attribute::WriteOnly) ||
            dataOperandHasImpliedAttr(OpNo, Attribute::ReadNone);
   }
 
   /// Extract the alignment of the return value.
-  MaybeAlign getRetAlign() const { return Attrs.getRetAlignment(); }
+  MaybeAlign getRetAlign() const {
+    if (auto Align = Attrs.getRetAlignment())
+      return Align;
+    if (const Function *F = getCalledFunction())
+      return F->getAttributes().getRetAlignment();
+    return None;
+  }
 
   /// Extract the alignment for a call or parameter (0=unknown).
   MaybeAlign getParamAlign(unsigned ArgNo) const {
     return Attrs.getParamAlignment(ArgNo);
   }
 
   MaybeAlign getParamStackAlign(unsigned ArgNo) const {
     return Attrs.getParamStackAlignment(ArgNo);

llvm/test/CodeGen/AMDGPU/GlobalISel/irtranslator-assert-align.ll

define void @declaration_result_align_8() {
   ; CHECK-NEXT:   $sgpr13 = COPY [[COPY14]](s32)
   ; CHECK-NEXT:   $sgpr14 = COPY [[COPY15]](s32)
   ; CHECK-NEXT:   $vgpr31 = COPY [[COPY16]](s32)
   ; CHECK-NEXT:   $sgpr30_sgpr31 = G_SI_CALL [[GV]](p0), @returns_ptr_align8, csr_amdgpu_highregs, implicit $sgpr0_sgpr1_sgpr2_sgpr3, implicit $sgpr4_sgpr5, implicit $sgpr6_sgpr7, implicit $sgpr8_sgpr9, implicit $sgpr10_sgpr11, implicit $sgpr12, implicit $sgpr13, implicit $sgpr14, implicit $vgpr31, implicit-def $vgpr0, implicit-def $vgpr1
   ; CHECK-NEXT:   [[COPY18:%[0-9]+]]:_(s32) = COPY $vgpr0
   ; CHECK-NEXT:   [[COPY19:%[0-9]+]]:_(s32) = COPY $vgpr1
   ; CHECK-NEXT:   [[MV:%[0-9]+]]:_(p1) = G_MERGE_VALUES [[COPY18]](s32), [[COPY19]](s32)
   ; CHECK-NEXT:   ADJCALLSTACKDOWN 0, 0, implicit-def $scc
-  ; CHECK-NEXT:   G_STORE [[C]](s8), [[MV]](p1) :: (store (s8) into %ir.ptr, align 8, addrspace 1)
+  ; CHECK-NEXT:   [[ASSERT_ALIGN:%[0-9]+]]:_(p1) = G_ASSERT_ALIGN [[MV]], 8
+  ; CHECK-NEXT:   G_STORE [[C]](s8), [[ASSERT_ALIGN]](p1) :: (store (s8) into %ir.ptr, align 8, addrspace 1)
   ; CHECK-NEXT:   [[COPY20:%[0-9]+]]:ccr_sgpr_64 = COPY [[COPY8]]
   ; CHECK-NEXT:   S_SETPC_B64_return [[COPY20]]
   %ptr = call i8 addrspace(1)* @returns_ptr_align8()
   store i8 0, i8 addrspace(1)* %ptr, align 8
   ret void
 }