[PATCH] D36604: PR34148: Do not assume we can use a copy relocation for an `external_weak` global
Richard Smith - zygoloid via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Aug 10 20:04:50 PDT 2017
rsmith created this revision.
Herald added a subscriber: sanjoy.
An `external_weak` global may be intended to resolve as a null pointer if it's not defined, so it doesn't make sense to use a copy relocation for it.
See also https://reviews.llvm.org/D36280 (which fixes an overlapping issue for X86).
Repository:
rL LLVM
https://reviews.llvm.org/D36604
Files:
lib/Target/TargetMachine.cpp
test/CodeGen/X86/global-access-pie-copyrelocs.ll
Index: test/CodeGen/X86/global-access-pie-copyrelocs.ll
===================================================================
--- test/CodeGen/X86/global-access-pie-copyrelocs.ll
+++ test/CodeGen/X86/global-access-pie-copyrelocs.ll
@@ -63,6 +63,20 @@
ret i32 %0
}
+; ExternalWeak Linkage
+ at e = extern_weak global i32, align 4
+
+define i32* @my_access_global_d() #0 {
+; X32-LABEL: my_access_global_d:
+; X32: addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %eax
+; X32: movl e at GOT(%eax), %eax
+; X64-LABEL: my_access_global_d:
+; X64: movq e at GOTPCREL(%rip), %rax
+
+entry:
+ ret i32* @e
+}
+
; External Linkage, only declaration, store a value.
define i32 @my_access_global_store_d() #0 {
Index: lib/Target/TargetMachine.cpp
===================================================================
--- lib/Target/TargetMachine.cpp
+++ lib/Target/TargetMachine.cpp
@@ -154,8 +154,9 @@
return true;
bool IsTLS = GV && GV->isThreadLocal();
- bool IsAccessViaCopyRelocs =
- Options.MCOptions.MCPIECopyRelocations && GV && isa<GlobalVariable>(GV);
+ bool IsAccessViaCopyRelocs = Options.MCOptions.MCPIECopyRelocations && GV &&
+ isa<GlobalVariable>(GV) &&
+ !GV->hasExternalWeakLinkage();
Triple::ArchType Arch = TT.getArch();
bool IsPPC =
Arch == Triple::ppc || Arch == Triple::ppc64 || Arch == Triple::ppc64le;
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