From d4718d5c9f9b5c41d88254429c61010c63139130 Mon Sep 17 00:00:00 2001 From: Joel Brobecker Date: Thu, 8 Nov 2018 10:27:31 -0500 Subject: [PATCH] (AArch64) wrong value returned by "finish" for HFA Consider the gdb.ada/array_return.exp testcase, and in particular, consider the following code... type Small_Float_Vector is array (1 .. 2) of Float; function Create_Small_Float_Vector return Small_Float_Vector is begin return (others => 4.25); end Create_Small_Float_Vector; ... which declares a type which is an array with 2 floats in it (floats are 4 bytes on AArch64), trying to get GDB to print the return value from that function does not work: (gdb) fin Run till exit from #0 pck.create_small_float_vector () at /[...]/pck.adb:15 0x000000000000062c in p () at /[...]/p.adb:11 11 Vector := Create_Small_Float_Vector; Value returned is $1 = (4.25, 0.0) ^^^ ||| We expected the value shown to be: (gdb) fin Run till exit from #0 pck.create_small_float_vector () at /[...]/pck.adb:15 0x000000000000062c in p () at /[...]/p.adb:11 11 Vector := Create_Small_Float_Vector; Value returned is $1 = (4.25, 4.25) Because the return type is an HFA, it is returned via the first two SIMD registers. However, what happens is that the current implementation fails to realize that this is an HFA, and therefore fetches the return value from the wrong location. And the reason why it fails to realize this is because it thinks that our array has 8 elements (HFAs have a maximum of 4). Looking at aapcs_is_vfp_call_or_return_candidate_1, where this is determined, we can easily see why (looks like a thinko): | case TYPE_CODE_ARRAY: | [...] | struct type *target_type = TYPE_TARGET_TYPE (type); | int count = aapcs_is_vfp_call_or_return_candidate_1 | (target_type, fundamental_type); | | if (count == -1) | return count; | !! -> | count *= TYPE_LENGTH (type); | return count; Here, we first determine the count for one element of our array, and so we should then be multiplying that count by the number of elements in our array (2 in our case). But instead, we multiply it by the total size (8). As a result, we do not classify the return type as an HFA, and thus pick the wrong location for fetching the return value. gdb/ChangeLog: * aarch64-tdep.c (aapcs_is_vfp_call_or_return_candidate_1): return the correct count for potential HFAs. Tested on aarch64-linux, fixes: array_return.exp: value printed by finish of Create_Small_Float_Vector --- gdb/ChangeLog | 5 +++++ gdb/aarch64-tdep.c | 2 +- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 6c18be9a747..be1b3d8c7ef 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2018-11-08 Joel Brobecker + + * aarch64-tdep.c (aapcs_is_vfp_call_or_return_candidate_1): + return the correct count for potential HFAs. + 2018-11-08 Jan Beulich * i387-tdep.c (i387_supply_xsave): Split handling of diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c index 0211930d7f0..51f1632eea7 100644 --- a/gdb/aarch64-tdep.c +++ b/gdb/aarch64-tdep.c @@ -1212,7 +1212,7 @@ aapcs_is_vfp_call_or_return_candidate_1 (struct type *type, if (count == -1) return count; - count *= TYPE_LENGTH (type); + count *= (TYPE_LENGTH (type) / TYPE_LENGTH (target_type)); return count; } } -- 2.30.2