[llvm] [X86] Set SHF_X86_64_LARGE for globals with explicit well-known large section name (PR #74381)
Arthur Eubanks via llvm-commits
llvm-commits at lists.llvm.org
Mon Dec 4 14:48:15 PST 2023
https://github.com/aeubanks created https://github.com/llvm/llvm-project/pull/74381
Globals marked with the .lbss/.ldata/.lrodata should automatically be treated as large.
Do this regardless of the code model for consistency when mixing object files compiled with different code models.
Basically the opposite of #70748.
Example in the wild:
https://codebrowser.dev/qt5/qtbase/src/testlib/qtestcase.cpp.html#1664
>From e18eb5e158804fa5ceba734e8f7d9bfac3332660 Mon Sep 17 00:00:00 2001
From: Arthur Eubanks <aeubanks at google.com>
Date: Mon, 4 Dec 2023 14:41:13 -0800
Subject: [PATCH] [X86] Set SHF_X86_64_LARGE for globals with explicit
well-known large section name
Globals marked with the .lbss/.ldata/.lrodata should automatically be treated as large.
Do this regardless of the code model for consistency when mixing object files compiled with different code models.
Basically the opposite of #70748.
Example in the wild:
https://codebrowser.dev/qt5/qtbase/src/testlib/qtestcase.cpp.html#1664
---
llvm/lib/Target/TargetMachine.cpp | 16 ++++++++-------
.../CodeGen/X86/code-model-elf-sections.ll | 20 +++++++++++++++++++
2 files changed, 29 insertions(+), 7 deletions(-)
diff --git a/llvm/lib/Target/TargetMachine.cpp b/llvm/lib/Target/TargetMachine.cpp
index f7096b708b39d..58a785434f659 100644
--- a/llvm/lib/Target/TargetMachine.cpp
+++ b/llvm/lib/Target/TargetMachine.cpp
@@ -43,9 +43,6 @@ bool TargetMachine::isLargeGlobalObject(const GlobalObject *GO) const {
if (getTargetTriple().getArch() != Triple::x86_64)
return false;
- if (getCodeModel() != CodeModel::Medium && getCodeModel() != CodeModel::Large)
- return false;
-
if (isa<Function>(GO))
return getCodeModel() == CodeModel::Large;
@@ -55,10 +52,10 @@ bool TargetMachine::isLargeGlobalObject(const GlobalObject *GO) const {
return false;
// Allowing large metadata sections in the presence of an explicit section is
- // useful, even if GCC does not allow them. However, we should not mark
- // certain well-known prefixes as large, because it would make the whole
- // output section large and cause the linker to move it, which is almost
- // always undesired.
+ // useful, even if GCC does not allow them. However, we should properly mark
+ // well-known section name prefixes as small/large, because otherwise the
+ // output section may have the wrong section flags and the linker will lay it
+ // out in an unexpected way.
StringRef Name = GV->getSection();
auto IsPrefix = [&](StringRef Prefix) {
StringRef S = Name;
@@ -66,6 +63,11 @@ bool TargetMachine::isLargeGlobalObject(const GlobalObject *GO) const {
};
if (IsPrefix(".bss") || IsPrefix(".data") || IsPrefix(".rodata"))
return false;
+ if (IsPrefix(".lbss") || IsPrefix(".ldata") || IsPrefix(".lrodata"))
+ return true;
+
+ if (getCodeModel() != CodeModel::Medium && getCodeModel() != CodeModel::Large)
+ return false;
const DataLayout &DL = GV->getParent()->getDataLayout();
uint64_t Size = DL.getTypeSizeInBits(GV->getValueType()) / 8;
diff --git a/llvm/test/CodeGen/X86/code-model-elf-sections.ll b/llvm/test/CodeGen/X86/code-model-elf-sections.ll
index 0b99a70c4044a..f72880e172bdc 100644
--- a/llvm/test/CodeGen/X86/code-model-elf-sections.ll
+++ b/llvm/test/CodeGen/X86/code-model-elf-sections.ll
@@ -21,9 +21,14 @@
; SMALL: .data {{.*}} WA {{.*}}
; SMALL: .data.x {{.*}} WA {{.*}}
; SMALL: .data0 {{.*}} WA {{.*}}
+; SMALL: .ldata {{.*}} WAl {{.*}}
+; SMALL: .ldata.x {{.*}} WAl {{.*}}
+; SMALL: .ldata0 {{.*}} WA {{.*}}
; SMALL: foo {{.*}} WA {{.*}}
; SMALL: .bss {{.*}} WA {{.*}}
+; SMALL: .lbss {{.*}} WAl {{.*}}
; SMALL: .rodata {{.*}} A {{.*}}
+; SMALL: .lrodata {{.*}} Al {{.*}}
; SMALL: .data.rel.ro {{.*}} WA {{.*}}
; SMALL: .tbss {{.*}} WAT {{.*}}
; SMALL: .tdata {{.*}} WAT {{.*}}
@@ -31,9 +36,14 @@
; SMALL-DS: .data {{.*}} WA {{.*}}
; SMALL-DS: .data.x {{.*}} WA {{.*}}
; SMALL-DS: .data0 {{.*}} WA {{.*}}
+; SMALL-DS: .ldata {{.*}} WAl {{.*}}
+; SMALL-DS: .ldata.x {{.*}} WAl {{.*}}
+; SMALL-DS: .ldata0 {{.*}} WA {{.*}}
; SMALL-DS: .data.data {{.*}} WA {{.*}}
; SMALL-DS: foo {{.*}} WA {{.*}}
+; SMALL-DS: .lbss {{.*}} WAl {{.*}}
; SMALL-DS: .bss.bss {{.*}} WA {{.*}}
+; SMALL-DS: .lrodata {{.*}} Al {{.*}}
; SMALL-DS: .rodata.rodata {{.*}} A {{.*}}
; SMALL-DS: .data.rel.ro.relro {{.*}} WA {{.*}}
; SMALL-DS: .tbss.tbss {{.*}} WAT {{.*}}
@@ -43,6 +53,8 @@
; LARGE: .data.x {{.*}} WA {{.*}}
; LARGE: .data0 {{.*}} WAl {{.*}}
; LARGE: .ldata {{.*}} WAl {{.*}}
+; LARGE: .ldata.x {{.*}} WAl {{.*}}
+; LARGE: .ldata0 {{.*}} WAl {{.*}}
; LARGE: foo {{.*}} WAl {{.*}}
; LARGE: .bss {{.*}} WA {{.*}}
; LARGE: .lbss {{.*}} WAl {{.*}}
@@ -55,6 +67,9 @@
; LARGE-DS: .data {{.*}} WA {{.*}}
; LARGE-DS: .data.x {{.*}} WA {{.*}}
; LARGE-DS: .data0 {{.*}} WAl {{.*}}
+; LARGE-DS: .ldata {{.*}} WAl {{.*}}
+; LARGE-DS: .ldata.x {{.*}} WAl {{.*}}
+; LARGE-DS: .ldata0 {{.*}} WAl {{.*}}
; LARGE-DS: .ldata.data {{.*}} WAl {{.*}}
; LARGE-DS: foo {{.*}} WAl {{.*}}
; LARGE-DS: .bss {{.*}} WA {{.*}}
@@ -71,11 +86,16 @@ target triple = "x86_64--linux"
@data_with_explicit_section = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0], section ".data"
@data_with_explicit_section2 = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0], section ".data.x"
@data_with_explicit_section0 = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0], section ".data0"
+ at ldata_with_explicit_section = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0], section ".ldata"
+ at ldata_with_explicit_section2 = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0], section ".ldata.x"
+ at ldata_with_explicit_section0 = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0], section ".ldata0"
@data = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0]
@foo_with_explicit_section = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0], section "foo"
@bss_with_explicit_section = internal global [10 x i64] zeroinitializer, section ".bss"
+ at lbss_with_explicit_section = internal global [10 x i64] zeroinitializer, section ".lbss"
@bss = internal global [10 x i64] zeroinitializer
@rodata_with_explicit_section = internal constant [10 x i64] zeroinitializer, section ".rodata"
+ at lrodata_with_explicit_section = internal constant [10 x i64] zeroinitializer, section ".lrodata"
@rodata = internal constant [10 x i64] zeroinitializer
@relro = internal constant [10 x ptr] [ptr @func, ptr @func, ptr @func, ptr @func, ptr @func, ptr @func, ptr @func, ptr @func, ptr @func, ptr @func]
@tbss = internal thread_local global [10 x i64] zeroinitializer
More information about the llvm-commits
mailing list