From 5111627ac1b0ae8a5a9d4dc1be8b22939ba850d0 Mon Sep 17 00:00:00 2001 From: Kostya Serebryany Date: Mon, 18 Mar 2013 09:38:39 +0000 Subject: [PATCH] [asan] when creating string constants, set unnamed_attr and align 1 so that equal strings are merged by the linker. Observed up to 1% binary size reduction. Thanks to Anton Korobeynikov for the suggestion git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177264 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Instrumentation/AddressSanitizer.cpp | 5 ++++- .../AddressSanitizer/do-not-instrument-internal-globals.ll | 5 +++-- 2 files changed, 7 insertions(+), 3 deletions(-) diff --git a/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/lib/Transforms/Instrumentation/AddressSanitizer.cpp index 614dc210a03..92b42ee64b0 100644 --- a/lib/Transforms/Instrumentation/AddressSanitizer.cpp +++ b/lib/Transforms/Instrumentation/AddressSanitizer.cpp @@ -531,9 +531,12 @@ static size_t TypeSizeToSizeIndex(uint32_t TypeSize) { // Create a constant for Str so that we can pass it to the run-time lib. static GlobalVariable *createPrivateGlobalForString(Module &M, StringRef Str) { Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str); - return new GlobalVariable(M, StrConst->getType(), true, + GlobalVariable *GV = new GlobalVariable(M, StrConst->getType(), true, GlobalValue::PrivateLinkage, StrConst, kAsanGenPrefix); + GV->setUnnamedAddr(true); // Ok to merge these. + GV->setAlignment(1); // Strings may not be merged w/o setting align 1. + return GV; } static bool GlobalWasGeneratedByAsan(GlobalVariable *G) { diff --git a/test/Instrumentation/AddressSanitizer/do-not-instrument-internal-globals.ll b/test/Instrumentation/AddressSanitizer/do-not-instrument-internal-globals.ll index 2efd6b1e0d1..0928c494154 100644 --- a/test/Instrumentation/AddressSanitizer/do-not-instrument-internal-globals.ll +++ b/test/Instrumentation/AddressSanitizer/do-not-instrument-internal-globals.ll @@ -14,6 +14,7 @@ entry: declare void @_Z3fooPi(i32*) ; We create one global string constant for the stack frame above. +; It should have unnamed_addr and align 1. ; Make sure we don't create any other global constants. -; CHECK: = private constant -; CHECK-NOT: = private constant +; CHECK: = private unnamed_addr constant{{.*}}align 1 +; CHECK-NOT: = private unnamed_addr constant -- 2.34.1