[gcc r11-6758] aix: default to DWARF 4.

[David Edelsohn]

https://gcc.gnu.org/g:56b5d13e27891ed1caec07826a07bb2e0621f914

commit r11-6758-g56b5d13e27891ed1caec07826a07bb2e0621f914
Author: David Edelsohn <dje.gcc@gmail.com>
Date:   Sun Jan 17 15:39:46 2021 -0500

    aix: default to DWARF 4.
    
    GCC now defaults to DWARF 5.  AIX only supports DWARF 4 (3.5).
    
    This patch overrides the default DWARF version to 4 unless explicitly
    stated.
    
    gcc/ChangeLog:
    
            * config/rs6000/aix71.h (SUBTARGET_OVERRIDE_OPTIONS): Override
            dwarf_version to 4.
            * config/rs6000/aix72.h (SUBTARGET_OVERRIDE_OPTIONS): Same.

Diff:
---
 gcc/config/rs6000/aix71.h | 3 +++
 gcc/config/rs6000/aix72.h | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/gcc/config/rs6000/aix71.h b/gcc/config/rs6000/aix71.h
index cb250e9871c..3612ed2593b 100644
--- a/gcc/config/rs6000/aix71.h
+++ b/gcc/config/rs6000/aix71.h
@@ -62,6 +62,9 @@ do {									\
       /* aix/ppc doesn't support -mvsx and -maltivec with Go */		\
       rs6000_isa_flags &= ~(OPTION_MASK_VSX | OPTION_MASK_ALTIVEC);	\
     }									\
+  if (!global_options_set.x_dwarf_version)				\
+    /* AIX only supports DWARF 4.  */					\
+    dwarf_version = 4;							\
 } while (0)
 
 #define ASM_SPEC32 "-a32"
diff --git a/gcc/config/rs6000/aix72.h b/gcc/config/rs6000/aix72.h
index 8bcaca47a7b..d34909283cc 100644
--- a/gcc/config/rs6000/aix72.h
+++ b/gcc/config/rs6000/aix72.h
@@ -62,6 +62,9 @@ do {									\
       /* aix/ppc doesn't support -mvsx and -maltivec with Go */		\
       rs6000_isa_flags &= ~(OPTION_MASK_VSX | OPTION_MASK_ALTIVEC);	\
     }									\
+  if (!global_options_set.x_dwarf_version)				\
+    /* AIX only supports DWARF 4.  */					\
+    dwarf_version = 4;							\
 } while (0)
 
 #define ASM_SPEC32 "-a32"