Bug 1800621 - Increase slop to prevent thunk out of range. r=firefox-build-system-reviewers,sergesanspaille

Differential Revision: https://phabricator.services.mozilla.com/D162259

build/build-clang/clang-15.json

@@ -13,6 +13,7 @@
         "revert-llvmorg-14-init-11890-gf86deb18cab6.patch",
         "win64-ret-null-on-commitment-limit_clang_14.patch",
         "llvmorg-16-init-7778-g232e0a011e8c.patch",
+        "llvmorg-16-init-10850-gff111a997f1b.patch",
         "compiler-rt-rss-limit-heap-profile.patch",
         "profdata-compat.patch"
     ]

build/build-clang/llvmorg-16-init-10850-gff111a997f1b.patch

@@ -0,0 +1,35 @@
+From ff111a997f1b40a531bc68b543542746d4b08a5f Mon Sep 17 00:00:00 2001
+From: Mike Hommey <mh@glandium.org>
+Date: Wed, 16 Nov 2022 21:31:28 -0500
+Subject: [PATCH] [lld-macho] Increase slop to prevent thunk out of range
+ again.
+
+Building Firefox with -O0 on arm64 mac recently hit the
+"FIXME: thunk range overrun" error on multiple occasions.
+
+Doubling or tripling slop was not sufficient in some cases, so
+quadruple it.
+
+Reviewed By: #lld-macho, int3
+
+Differential Revision: https://reviews.llvm.org/D138174
+---
+ lld/MachO/ConcatOutputSection.cpp | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/lld/MachO/ConcatOutputSection.cpp b/lld/MachO/ConcatOutputSection.cpp
+index e97f1e9b9ddd..cbd3a2492d25 100644
+--- a/lld/MachO/ConcatOutputSection.cpp
++++ b/lld/MachO/ConcatOutputSection.cpp
+@@ -246,7 +246,7 @@ void TextOutputSection::finalize() {
+     // contains several branch instructions in succession, then the distance
+     // from the current position to the position where the thunks are inserted
+     // grows. So leave room for a bunch of thunks.
+-    unsigned slop = 256 * thunkSize;
++    unsigned slop = 1024 * thunkSize;
+     while (finalIdx < endIdx && addr + size + inputs[finalIdx]->getSize() <
+                                     isecVA + forwardBranchRange - slop)
+       finalizeOne(inputs[finalIdx++]);
+-- 
+2.38.1.1.g6d9df9d320
+