Skip to content

[X86] Change how we treat functions with explicit sections as small/large #88172

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Apr 16, 2024
Merged

[X86] Change how we treat functions with explicit sections as small/large #88172

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
838f4b1
[X86] Change how we treat functions with explicit sections as small/l…
aeubanks Apr 8, 2024
fa0655b
add comment
aeubanks Apr 16, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
26 changes: 20 additions & 6 deletions llvm/lib/Target/TargetMachine.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,12 @@ bool TargetMachine::isLargeGlobalValue(const GlobalValue *GVal) const {
if (getTargetTriple().getArch() != Triple::x86_64)
return false;

// Remaining logic below is ELF-specific. For other object file formats where
// the large code model is mostly used for JIT compilation, just look at the
// code model.
if (!getTargetTriple().isOSBinFormatELF())
Copy link
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Please add a comment about what's going on here. Essentially, all the logic below is ELF-specific. The large code model is supported with other object file formats mainly for the benefit of JIT compilation, and for that we fall back to the global code model option.

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

done

return getCodeModel() == CodeModel::Large;

auto *GO = GVal->getAliaseeObject();

// Be conservative if we can't find an underlying GlobalObject.
Expand All @@ -51,9 +57,20 @@ bool TargetMachine::isLargeGlobalValue(const GlobalValue *GVal) const {

auto *GV = dyn_cast<GlobalVariable>(GO);

auto IsPrefix = [](StringRef Name, StringRef Prefix) {
return Name.consume_front(Prefix) && (Name.empty() || Name[0] == '.');
};

// Functions/GlobalIFuncs are only large under the large code model.
if (!GV)
if (!GV) {
// Handle explicit sections as we do for GlobalVariables with an explicit
// section, see comments below.
if (GO->hasSection()) {
StringRef Name = GO->getSection();
return IsPrefix(Name, ".ltext");
}
return getCodeModel() == CodeModel::Large;
}

if (GV->isThreadLocal())
return false;
Expand All @@ -73,11 +90,8 @@ bool TargetMachine::isLargeGlobalValue(const GlobalValue *GVal) const {
// data sections. The code model attribute overrides this above.
if (GV->hasSection()) {
StringRef Name = GV->getSection();
auto IsPrefix = [&](StringRef Prefix) {
StringRef S = Name;
return S.consume_front(Prefix) && (S.empty() || S[0] == '.');
};
return IsPrefix(".lbss") || IsPrefix(".ldata") || IsPrefix(".lrodata");
return IsPrefix(Name, ".lbss") || IsPrefix(Name, ".ldata") ||
IsPrefix(Name, ".lrodata");
}

// Respect large data threshold for medium and large code models.
Expand Down
23 changes: 23 additions & 0 deletions llvm/test/CodeGen/X86/code-model-elf-text-sections.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -13,13 +13,36 @@
; RUN: llvm-readelf -S %t | FileCheck %s --check-prefix=LARGE-DS

; SMALL: .text {{.*}} AX {{.*}}
; SMALL: .ltext {{.*}} AXl {{.*}}
; SMALL: .ltext.2 {{.*}} AXl {{.*}}
; SMALL: .foo {{.*}} AX {{.*}}
; SMALL-DS: .text.func {{.*}} AX {{.*}}
; SMALL-DS: .ltext {{.*}} AXl {{.*}}
; SMALL-DS: .ltext.2 {{.*}} AXl {{.*}}
; SMALL-DS: .foo {{.*}} AX {{.*}}
; LARGE: .ltext {{.*}} AXl {{.*}}
; LARGE: .ltext.2 {{.*}} AXl {{.*}}
; LARGE: .foo {{.*}} AX {{.*}}
; LARGE-DS: .ltext.func {{.*}} AXl {{.*}}
; LARGE-DS: .ltext {{.*}} AXl {{.*}}
; LARGE-DS: .ltext.2 {{.*}} AXl {{.*}}
; LARGE-DS: .foo {{.*}} AX {{.*}}

target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64--linux"

define void @func() {
ret void
}

define void @ltext() section ".ltext" {
ret void
}

define void @ltext2() section ".ltext.2" {
ret void
}

define void @foo() section ".foo" {
ret void
}