New llc option pie-copy-relocations to optimize access to extern globals.
This option indicates copy relocations support is available from the linker
when building as PIE and allows accesses to extern globals to avoid the GOT.
Differential Revision: https://reviews.llvm.org/D24849
llvm-svn: 284160
diff --git a/llvm/include/llvm/MC/MCTargetOptions.h b/llvm/include/llvm/MC/MCTargetOptions.h
index fd4c6e4..21091b3 100644
--- a/llvm/include/llvm/MC/MCTargetOptions.h
+++ b/llvm/include/llvm/MC/MCTargetOptions.h
@@ -41,6 +41,7 @@
bool MCSaveTempLabels : 1;
bool MCUseDwarfDirectory : 1;
bool MCIncrementalLinkerCompatible : 1;
+ bool MCPIECopyRelocations : 1;
bool ShowMCEncoding : 1;
bool ShowMCInst : 1;
bool AsmVerbose : 1;
@@ -67,6 +68,7 @@
ARE_EQUAL(MCSaveTempLabels) &&
ARE_EQUAL(MCUseDwarfDirectory) &&
ARE_EQUAL(MCIncrementalLinkerCompatible) &&
+ ARE_EQUAL(MCPIECopyRelocations) &&
ARE_EQUAL(ShowMCEncoding) &&
ARE_EQUAL(ShowMCInst) &&
ARE_EQUAL(AsmVerbose) &&
diff --git a/llvm/include/llvm/MC/MCTargetOptionsCommandFlags.h b/llvm/include/llvm/MC/MCTargetOptionsCommandFlags.h
index 801dd6a..cb02084 100644
--- a/llvm/include/llvm/MC/MCTargetOptionsCommandFlags.h
+++ b/llvm/include/llvm/MC/MCTargetOptionsCommandFlags.h
@@ -38,6 +38,8 @@
"When used with filetype=obj, "
"emit an object file which can be used with an incremental linker"));
+cl::opt<bool> PIECopyRelocations("pie-copy-relocations", cl::desc("PIE Copy Relocations"));
+
cl::opt<int> DwarfVersion("dwarf-version", cl::desc("Dwarf version"),
cl::init(0));
@@ -62,6 +64,7 @@
(AsmInstrumentation == MCTargetOptions::AsmInstrumentationAddress);
Options.MCRelaxAll = RelaxAll;
Options.MCIncrementalLinkerCompatible = IncrementalLinkerCompatible;
+ Options.MCPIECopyRelocations = PIECopyRelocations;
Options.DwarfVersion = DwarfVersion;
Options.ShowMCInst = ShowMCInst;
Options.ABIName = ABIName;
diff --git a/llvm/lib/MC/MCTargetOptions.cpp b/llvm/lib/MC/MCTargetOptions.cpp
index 1d956a8..e847a17 100644
--- a/llvm/lib/MC/MCTargetOptions.cpp
+++ b/llvm/lib/MC/MCTargetOptions.cpp
@@ -16,7 +16,8 @@
: SanitizeAddress(false), MCRelaxAll(false), MCNoExecStack(false),
MCFatalWarnings(false), MCNoWarn(false), MCSaveTempLabels(false),
MCUseDwarfDirectory(false), MCIncrementalLinkerCompatible(false),
- ShowMCEncoding(false), ShowMCInst(false), AsmVerbose(false),
+ MCPIECopyRelocations(false), ShowMCEncoding(false),
+ ShowMCInst(false), AsmVerbose(false),
PreserveAsmComments(true), DwarfVersion(0), ABIName() {}
StringRef MCTargetOptions::getABIName() const {
diff --git a/llvm/lib/Target/TargetMachine.cpp b/llvm/lib/Target/TargetMachine.cpp
index 43a587b..792280a 100644
--- a/llvm/lib/Target/TargetMachine.cpp
+++ b/llvm/lib/Target/TargetMachine.cpp
@@ -115,9 +115,6 @@
llvm_unreachable("invalid TLS model");
}
-// FIXME: make this a proper option
-static bool CanUseCopyRelocWithPIE = false;
-
bool TargetMachine::shouldAssumeDSOLocal(const Module &M,
const GlobalValue *GV) const {
Reloc::Model RM = getRelocationModel();
@@ -154,8 +151,10 @@
return true;
bool IsTLS = GV && GV->isThreadLocal();
+ bool IsAccessViaCopyRelocs =
+ Options.MCOptions.MCPIECopyRelocations && GV && isa<GlobalVariable>(GV);
// Check if we can use copy relocations.
- if (!IsTLS && (RM == Reloc::Static || CanUseCopyRelocWithPIE))
+ if (!IsTLS && (RM == Reloc::Static || IsAccessViaCopyRelocs))
return true;
}
diff --git a/llvm/test/CodeGen/X86/global-access-pie-copyrelocs.ll b/llvm/test/CodeGen/X86/global-access-pie-copyrelocs.ll
new file mode 100644
index 0000000..5c4a87c
--- /dev/null
+++ b/llvm/test/CodeGen/X86/global-access-pie-copyrelocs.ll
@@ -0,0 +1,119 @@
+; RUN: llc < %s -march=x86-64 -mcpu=generic -mtriple=x86_64-linux-gnu -relocation-model=pic -pie-copy-relocations \
+; RUN: | FileCheck -check-prefix=X64 %s
+; RUN: llc < %s -emulated-tls -march=x86 -mcpu=generic -mtriple=i386-linux-gnu -relocation-model=pic -pie-copy-relocations \
+; RUN: | FileCheck -check-prefix=X32 %s
+
+; External Linkage
+@a = global i32 0, align 4
+
+define i32 @my_access_global_a() #0 {
+; X32-LABEL: my_access_global_a:
+; X32: addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %eax
+; X32-NEXT: movl a@GOTOFF(%eax), %eax
+; X64-LABEL: my_access_global_a:
+; X64: movl a(%rip), %eax
+
+entry:
+ %0 = load i32, i32* @a, align 4
+ ret i32 %0
+}
+
+; WeakAny Linkage
+@b = weak global i32 0, align 4
+
+define i32 @my_access_global_b() #0 {
+; X32-LABEL: my_access_global_b:
+; X32: addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %eax
+; X32-NEXT: movl b@GOTOFF(%eax), %eax
+; X64-LABEL: my_access_global_b:
+; X64: movl b(%rip), %eax
+
+entry:
+ %0 = load i32, i32* @b, align 4
+ ret i32 %0
+}
+
+; Internal Linkage
+@c = internal global i32 0, align 4
+
+define i32 @my_access_global_c() #0 {
+; X32-LABEL: my_access_global_c:
+; X32: addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %eax
+; X32-NEXT: movl c@GOTOFF(%eax), %eax
+; X64-LABEL: my_access_global_c:
+; X64: movl c(%rip), %eax
+
+entry:
+ %0 = load i32, i32* @c, align 4
+ ret i32 %0
+}
+
+; External Linkage, only declaration.
+@d = external global i32, align 4
+
+define i32 @my_access_global_load_d() #0 {
+; X32-LABEL: my_access_global_load_d:
+; X32: addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %eax
+; X32-NEXT: movl d@GOTOFF(%eax), %eax
+; X64-LABEL: my_access_global_load_d:
+; X64: movl d(%rip), %eax
+
+entry:
+ %0 = load i32, i32* @d, align 4
+ ret i32 %0
+}
+
+; External Linkage, only declaration, store a value.
+
+define i32 @my_access_global_store_d() #0 {
+; X32-LABEL: my_access_global_store_d:
+; X32: addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %eax
+; X32-NEXT: movl $2, d@GOTOFF(%eax)
+; X64-LABEL: my_access_global_store_d:
+; X64: movl $2, d(%rip)
+
+entry:
+ store i32 2, i32* @d, align 4
+ ret i32 0
+}
+
+; External Linkage, function pointer access.
+declare i32 @access_fp(i32 ()*)
+declare i32 @foo()
+
+define i32 @my_access_fp_foo() #0 {
+; X32-LABEL: my_access_fp_foo:
+; X32: addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %ebx
+; X32-NEXT: movl foo@GOT(%ebx), %eax
+; X64-LABEL: my_access_fp_foo:
+; X64: movq foo@GOTPCREL(%rip), %rdi
+
+entry:
+ %call = call i32 @access_fp(i32 ()* @foo)
+ ret i32 %call
+}
+
+; LinkOnceODR Linkage, function pointer access.
+
+$bar = comdat any
+
+define linkonce_odr i32 @bar() comdat {
+entry:
+ ret i32 0
+}
+
+define i32 @my_access_fp_bar() #0 {
+; X32-LABEL: my_access_fp_bar:
+; X32: addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %ebx
+; X32-NEXT: leal bar@GOTOFF(%ebx), %eax
+; X64-LABEL: my_access_fp_bar:
+; X64: leaq bar(%rip), %rdi
+
+entry:
+ %call = call i32 @access_fp(i32 ()* @bar)
+ ret i32 %call
+}
+
+!llvm.module.flags = !{!0, !1}
+!0 = !{i32 1, !"PIC Level", i32 1}
+!1 = !{i32 1, !"PIE Level", i32 1}