[ARM] GlobalISel: Support struct params/returns

Very very similar to the support for arrays. As with arrays, we don't
support returning large structs that wouldn't fit in R0-R3. Most
front-ends would likely use sret arguments for that anyway.

The only significant difference is that when splitting a struct, we need
to make sure we set the correct original alignment on each member,
otherwise it may get split incorrectly between stack and registers.

llvm-svn: 304536

1 files changed, 9 insertions, 4 deletions

diff --git a/llvm/test/CodeGen/ARM/GlobalISel/arm-unsupported.ll b/llvm/test/CodeGen/ARM/GlobalISel/arm-unsupported.ll
index ef30cb1063f..34f00aebe1b 100644
--- a/llvm/test/CodeGen/ARM/GlobalISel/arm-unsupported.ll
+++ b/llvm/test/CodeGen/ARM/GlobalISel/arm-unsupported.ll
@@ -54,10 +54,15 @@ define [16 x i32] @test_ret_demotion() {
   ret [16 x i32] %res
 }
 
-define void @test_structs({i32, i32} %struct) {
-; CHECK: remark: {{.*}} unable to lower arguments: void ({ i32, i32 })*
-; CHECK-LABEL: warning: Instruction selection used fallback path for test_structs
-  ret void
+%large.struct = type { i32, i32, i32, i32, i32} ; Doesn't fit in R0-R3
+
+declare %large.struct @large_struct_return_target()
+
+define %large.struct @test_large_struct_return() {
+; CHECK: remark: {{.*}} unable to translate instruction: call{{.*}} @large_struct_return_target
+; CHECK-LABEL: warning: Instruction selection used fallback path for test_large_struct_return
+  %r = call %large.struct @large_struct_return_target()
+  ret %large.struct %r
 }
 
 define void @test_vararg_definition(i32 %a, ...) {