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[Darwin,machopic,4/n,committed] Arrange to indirect IVARs when needed.

Message ID B120C65B-591E-49A0-B4BD-E60935A5FBD0@sandoe.co.uk
State New
Headers show
Series [Darwin,machopic,4/n,committed] Arrange to indirect IVARs when needed. | expand

Commit Message

Iain Sandoe Oct. 10, 2019, 7:25 p.m. UTC 
Objective C V2 (m64) IVAR offset refs from Apple GCC-4.x have an indirection
for m64 code on PPC (which is the only 64b user for Mach-O PIC).  Apple GCC
4.x places the indirections in the .data section, however this seems to have
been unintentional - and we are placing the indirections in the non-lazy
symbol pointers section as usual.

If Mike can recall any reason that they should be in the .data section, we can
revise that - but testing hasn’t revealed any issues so far.

Tested on x86_64-darwin16, powerpc-darwin9.
applied to mainline.
thanks,
Iain

gcc/ChangeLog:

2019-10-10  Iain Sandoe  <iain@sandoe.co.uk>

	* config/darwin.c: Lookup Objective C metadata and force indirection
	for IVAR refs.

Comments

Mike Stump Oct. 11, 2019, 5:40 p.m. UTC | #1 
On Oct 10, 2019, at 12:25 PM, Iain Sandoe <iain@sandoe.co.uk> wrote:
> 
> Objective C V2 (m64) IVAR offset refs from Apple GCC-4.x have an indirection
> for m64 code on PPC (which is the only 64b user for Mach-O PIC).  Apple GCC
> 4.x places the indirections in the .data section, however this seems to have
> been unintentional - and we are placing the indirections in the non-lazy
> symbol pointers section as usual.
> 
> If Mike can recall any reason that they should be in the .data section, we can
> revise that - but testing hasn’t revealed any issues so far.

Don't recall any reason.
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Patch

diff --git a/gcc/REVISION b/gcc/REVISION
index a7c33b8bba..44c108c456 100644
--- a/gcc/REVISION
+++ b/gcc/REVISION
@@ -1 +1 @@ 
-[trunk revision 276847]
+[trunk revision 276848]
diff --git a/gcc/config/darwin.c b/gcc/config/darwin.c
index f490f622fc..539ef759d3 100644
--- a/gcc/config/darwin.c
+++ b/gcc/config/darwin.c
@@ -1270,6 +1270,17 @@  darwin_encode_section_info (tree decl, rtx rtl, int first)
       || (DECL_WEAK (decl) && ! MACHO_SYMBOL_HIDDEN_VIS_P (sym_ref))
       || lookup_attribute ("weakref", DECL_ATTRIBUTES (decl)))
      SYMBOL_REF_FLAGS (sym_ref) |= MACHO_SYMBOL_FLAG_MUST_INDIRECT;
+
+#if DARWIN_PPC
+  /* Objective C V2 (m64) IVAR offset refs from Apple GCC-4.x have an
+     indirection for m64 code on PPC.  Historically, these indirections
+     also appear in the .data section.  */
+  tree o2meta = lookup_attribute ("OBJC2META", DECL_ATTRIBUTES (decl));
+  o2meta = o2meta ? TREE_VALUE (o2meta) : NULL_TREE;
+
+  if (o2meta && strncmp (IDENTIFIER_POINTER (o2meta), "V2_IVRF",7) == 0)
+    SYMBOL_REF_FLAGS (sym_ref) |= MACHO_SYMBOL_FLAG_MUST_INDIRECT;
+#endif
 }
 
 void