[gcc r14-9907] btf: do not skip members of data type with type id BTF_VOID_TYPEID

[gcc r14-9907] btf: do not skip members of data type with type id BTF_VOID_TYPEID

[Indu Bhagat]

https://gcc.gnu.org/g:936dd627cd90bdfa3f796712c043406958131d7c

commit r14-9907-g936dd627cd90bdfa3f796712c043406958131d7c
Author: Indu Bhagat <indu.bhagat@oracle.com>
Date:   Mon Apr 8 11:01:45 2024 -0700

    btf: do not skip members of data type with type id BTF_VOID_TYPEID
    
    The previous fix in gen_ctf_sou_type () exposes an issue in BTF
    generation, however: BTF emission was currently decrementing the vlen
    (indicating the number of members) to skip members of type CTF_K_UNKNOWN
    altogether, but still emitting the BTF for the corresponding member (in
    output_asm_btf_sou_fields ()).
    
    One can see malformed BTF by executing the newly added CTF testcase
    (gcc.dg/debug/ctf/ctf-bitfields-5.c) with -gbtf instead or even existing
    btf-struct-2.c without this patch.
    
    To fix the issue, it makes sense to rather _not_ skip members of data
    type of type id BTF_VOID_TYPEID.
    
    gcc/ChangeLog:
            * btfout.cc (btf_asm_type): Do not skip emitting members of
            unknown type.
    
    gcc/testsuite/ChangeLog:
            * gcc.dg/debug/btf/btf-bitfields-4.c: Update the vlen check.
            * gcc.dg/debug/btf/btf-struct-2.c: Check that member named 'f'
            with void data type is emitted.

Diff:
---
 gcc/btfout.cc                                    | 5 -----
 gcc/testsuite/gcc.dg/debug/btf/btf-bitfields-4.c | 6 +++---
 gcc/testsuite/gcc.dg/debug/btf/btf-struct-2.c    | 9 +++++----
 3 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/gcc/btfout.cc b/gcc/btfout.cc
index 4a8ec4d1ff0..ab491f0297f 100644
--- a/gcc/btfout.cc
+++ b/gcc/btfout.cc
@@ -820,11 +820,6 @@ btf_asm_type (ctf_container_ref ctfc, ctf_dtdef_ref dtd)
 	  /* Set kflag if this member is a representable bitfield.  */
 	  if (btf_dmd_representable_bitfield_p (ctfc, dmd))
 	    btf_kflag = 1;
-
-	  /* Struct members that refer to unsupported types or bitfield formats
-	     shall be skipped. These are marked during preprocessing.  */
-	  else if (!btf_emit_id_p (dmd->dmd_type))
-	    btf_vlen -= 1;
 	}
     }
 
diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-bitfields-4.c b/gcc/testsuite/gcc.dg/debug/btf/btf-bitfields-4.c
index c00c8b3d87f..d4a6ef6a1eb 100644
--- a/gcc/testsuite/gcc.dg/debug/btf/btf-bitfields-4.c
+++ b/gcc/testsuite/gcc.dg/debug/btf/btf-bitfields-4.c
@@ -6,14 +6,14 @@
    In this test, we construct a structure such that the bitfield will have
    an offset so large as to be unrepresentable in BTF. We expect that the
    resulting BTF will describe the rest of the structure, ignoring the
-   non-representable bitfield.  */
+   non-representable bitfield by simply using void data type for the same.  */
 
 /* { dg-do compile } */
 /* { dg-options "-O0 -gbtf -dA" } */
 /* { dg-require-effective-target size32plus } */
 
-/* Struct with 3 members and no bitfield (kind_flag not set).  */
-/* { dg-final { scan-assembler-times "\[\t \]0x4000003\[\t \]+\[^\n\]*btt_info" 1 } } */
+/* Struct with 4 members and no bitfield (kind_flag not set).  */
+/* { dg-final { scan-assembler-times "\[\t \]0x4000004\[\t \]+\[^\n\]*btt_info" 1 } } */
 
 struct bigly
 {
diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-struct-2.c b/gcc/testsuite/gcc.dg/debug/btf/btf-struct-2.c
index e9ff06883db..fa7231be75c 100644
--- a/gcc/testsuite/gcc.dg/debug/btf/btf-struct-2.c
+++ b/gcc/testsuite/gcc.dg/debug/btf/btf-struct-2.c
@@ -2,14 +2,15 @@
    unsupported type.
 
    BTF does not support vector types (among other things). When
-   generating BTF for a struct (or union) type, members which refer to
-   unsupported types should be skipped.  */
+   generating BTF for a struct (or union) type.  Members which refer to
+   unsupported types should not be skipped, however.  */
 
 /* { dg-do compile } */
 /* { dg-options "-O0 -gbtf -dA" } */
 
-/* Expect a struct with only 2 members - 'f' should not be present.  */
-/* { dg-final { scan-assembler-times "\[\t \]0x4000002\[\t \]+\[^\n\]*btt_info" 1 } } */
+/* Expect a struct with 3 members - 'f' is present but is of data type void.  */
+/* { dg-final { scan-assembler-times "\[\t \]0x4000003\[\t \]+\[^\n\]*btt_info" 1 } } */
+/* { dg-final { scan-assembler-times " MEMBER 'f' idx=1\[\\r\\n\]+\[^\\r\\n\]*0\[\t \]+\[^\n\]*btm_type: void" 1 } } */
 
 struct with_float
 {