[flang-commits] [flang] [flang] fix AArch64 PCS for struct following pointer (PR #127802)

[David Truby via flang-commits]

https://github.com/DavidTruby created https://github.com/llvm/llvm-project/pull/127802

Pointers are already handled as taking up a register in the ABI handling, but the handling for structs was not taking this into account. This patch changes the struct handling to acknowledge that pointer arguments take up an integer register.

Fixes #123075

>From a4cb6f3462d51f6e1a528a4cb91286f83c883681 Mon Sep 17 00:00:00 2001
From: David Truby <david.truby at arm.com>
Date: Tue, 18 Feb 2025 17:24:30 +0000
Subject: [PATCH] [flang] fix AArch64 PCS for struct following pointer

Pointers are already handled as taking up a register in the ABI
handling, but the handling for structs was not taking this into account.
This patch changes the struct handling to acknowledge that pointer
arguments take up an integer register.

Fixes #123075
---
 flang/lib/Optimizer/CodeGen/Target.cpp          |  7 +++++++
 flang/test/Fir/struct-passing-aarch64-byval.fir | 14 ++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/flang/lib/Optimizer/CodeGen/Target.cpp b/flang/lib/Optimizer/CodeGen/Target.cpp
index 1bc673bb34e32..2a1eb0bc33f5c 100644
--- a/flang/lib/Optimizer/CodeGen/Target.cpp
+++ b/flang/lib/Optimizer/CodeGen/Target.cpp
@@ -930,6 +930,13 @@ struct TargetAArch64 : public GenericTarget<TargetAArch64> {
         .Case<fir::VectorType>([&](auto) {
           TODO(loc, "passing vector argument to C by value is not supported");
           return NRegs{};
+        })
+        .Default([&](auto ty) {
+          if (fir::conformsWithPassByRef(ty))
+            return NRegs{1, false}; // Pointers take 1 integer register
+          TODO(loc, "unsupported component type for BIND(C), VALUE derived "
+                    "type argument");
+          return NRegs{};
         });
   }
 
diff --git a/flang/test/Fir/struct-passing-aarch64-byval.fir b/flang/test/Fir/struct-passing-aarch64-byval.fir
index 27143459dde2f..087efba393014 100644
--- a/flang/test/Fir/struct-passing-aarch64-byval.fir
+++ b/flang/test/Fir/struct-passing-aarch64-byval.fir
@@ -71,3 +71,17 @@ func.func private @too_many_hfa(!fir.type<hfa_max{i:f128,j:f128,k:f128,l:f128}>,
 
 // CHECK-LABEL: func.func private @too_big(!fir.ref<!fir.type<too_big{i:!fir.array<5xi32>}>> {{{.*}}, llvm.byval = !fir.type<too_big{i:!fir.array<5xi32>}>})
 func.func private @too_big(!fir.type<too_big{i:!fir.array<5xi32>}>)
+
+// CHECK-LABEL: func.func private @pointer_type(!fir.ref<i64>, !fir.array<1xi64>)
+func.func private @pointer_type(!fir.ref<i64>, !fir.type<pointer_type{i:i64}>)
+
+// CHECK-LABEL: func.func private @pointer_type_too_many_int(!fir.ref<i64>, 
+// CHECK-SAME: !fir.array<2xi64>,
+// CHECK-SAME: !fir.array<2xi64>,
+// CHECK-SAME: !fir.array<2xi64>,
+// CHECK-SAME: !fir.ref<!fir.type<int_max{i:i64,j:i64}>> {{{.*}}, llvm.byval = !fir.type<int_max{i:i64,j:i64}>})
+func.func private @pointer_type_too_many_int(!fir.ref<i64>,
+                       !fir.type<int_max{i:i64,j:i64}>,
+                       !fir.type<int_max{i:i64,j:i64}>,
+                       !fir.type<int_max{i:i64,j:i64}>,
+                       !fir.type<int_max{i:i64,j:i64}>)