[lld] r296534 - ELF ICF: Merge only functions.
Rui Ueyama via llvm-commits
llvm-commits at lists.llvm.org
Tue Feb 28 14:42:49 PST 2017
Author: ruiu
Date: Tue Feb 28 16:42:49 2017
New Revision: 296534
URL: http://llvm.org/viewvc/llvm-project?rev=296534&view=rev
Log:
ELF ICF: Merge only functions.
Previously, LLD merged all read-only sections. So the following
program prints out "true" if -icf=all is specified.
static const int foo = 1;
static const int bar = 1;
int main() { printf("%s\n", &foo == &bar ? "true" : "false"); }
This is somewhat counter-intuitive, and it actually caused nasty issues.
One example is https://bugs.chromium.org/p/chromium/issues/detail?id=682773#c24.
This patch changes the way how it works. Now ICF merges only functions
(i.e. executable sections).
Differential Revision: https://reviews.llvm.org/D30365
Added:
lld/trunk/test/ELF/icf9.s
Modified:
lld/trunk/ELF/ICF.cpp
Modified: lld/trunk/ELF/ICF.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/ICF.cpp?rev=296534&r1=296533&r2=296534&view=diff
==============================================================================
--- lld/trunk/ELF/ICF.cpp (original)
+++ lld/trunk/ELF/ICF.cpp Tue Feb 28 16:42:49 2017
@@ -162,8 +162,8 @@ static bool isEligible(InputSection *S)
// .init and .fini contains instructions that must be executed to
// initialize and finalize the process. They cannot and should not
// be merged.
- return S->Live && (S->Flags & SHF_ALLOC) && !(S->Flags & SHF_WRITE) &&
- S->Name != ".init" && S->Name != ".fini";
+ return S->Live && (S->Flags & SHF_ALLOC) && (S->Flags & SHF_EXECINSTR) &&
+ !(S->Flags & SHF_WRITE) && S->Name != ".init" && S->Name != ".fini";
}
// Split an equivalence class into smaller classes.
Added: lld/trunk/test/ELF/icf9.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/icf9.s?rev=296534&view=auto
==============================================================================
--- lld/trunk/test/ELF/icf9.s (added)
+++ lld/trunk/test/ELF/icf9.s Tue Feb 28 16:42:49 2017
@@ -0,0 +1,20 @@
+# REQUIRES: x86
+
+### Make sure that we do not merge data.
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+# RUN: ld.lld %t -o %t2 --icf=all --verbose | FileCheck %s
+
+# CHECK-NOT: selected .data.d1
+# CHECK-NOT: selected .data.d2
+
+.globl _start, d1, d2
+_start:
+ ret
+
+.section .data.f1, "a"
+d1:
+ .byte 1
+
+.section .data.f2, "a"
+d2:
+ .byte 1
More information about the llvm-commits
mailing list