[llvm] r284160 - New llc option pie-copy-relocations to optimize access to extern globals.
Sriraman Tallam via llvm-commits
llvm-commits at lists.llvm.org
Thu Oct 13 13:54:39 PDT 2016
Author: tmsriram
Date: Thu Oct 13 15:54:39 2016
New Revision: 284160
URL: http://llvm.org/viewvc/llvm-project?rev=284160&view=rev
Log:
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
Added:
llvm/trunk/test/CodeGen/X86/global-access-pie-copyrelocs.ll
Modified:
llvm/trunk/include/llvm/MC/MCTargetOptions.h
llvm/trunk/include/llvm/MC/MCTargetOptionsCommandFlags.h
llvm/trunk/lib/MC/MCTargetOptions.cpp
llvm/trunk/lib/Target/TargetMachine.cpp
Modified: llvm/trunk/include/llvm/MC/MCTargetOptions.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCTargetOptions.h?rev=284160&r1=284159&r2=284160&view=diff
==============================================================================
--- llvm/trunk/include/llvm/MC/MCTargetOptions.h (original)
+++ llvm/trunk/include/llvm/MC/MCTargetOptions.h Thu Oct 13 15:54:39 2016
@@ -41,6 +41,7 @@ public:
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 @@ inline bool operator==(const MCTargetOpt
ARE_EQUAL(MCSaveTempLabels) &&
ARE_EQUAL(MCUseDwarfDirectory) &&
ARE_EQUAL(MCIncrementalLinkerCompatible) &&
+ ARE_EQUAL(MCPIECopyRelocations) &&
ARE_EQUAL(ShowMCEncoding) &&
ARE_EQUAL(ShowMCInst) &&
ARE_EQUAL(AsmVerbose) &&
Modified: llvm/trunk/include/llvm/MC/MCTargetOptionsCommandFlags.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCTargetOptionsCommandFlags.h?rev=284160&r1=284159&r2=284160&view=diff
==============================================================================
--- llvm/trunk/include/llvm/MC/MCTargetOptionsCommandFlags.h (original)
+++ llvm/trunk/include/llvm/MC/MCTargetOptionsCommandFlags.h Thu Oct 13 15:54:39 2016
@@ -38,6 +38,8 @@ cl::opt<bool> IncrementalLinkerCompatibl
"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 @@ static inline MCTargetOptions InitMCTarg
(AsmInstrumentation == MCTargetOptions::AsmInstrumentationAddress);
Options.MCRelaxAll = RelaxAll;
Options.MCIncrementalLinkerCompatible = IncrementalLinkerCompatible;
+ Options.MCPIECopyRelocations = PIECopyRelocations;
Options.DwarfVersion = DwarfVersion;
Options.ShowMCInst = ShowMCInst;
Options.ABIName = ABIName;
Modified: llvm/trunk/lib/MC/MCTargetOptions.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCTargetOptions.cpp?rev=284160&r1=284159&r2=284160&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCTargetOptions.cpp (original)
+++ llvm/trunk/lib/MC/MCTargetOptions.cpp Thu Oct 13 15:54:39 2016
@@ -16,7 +16,8 @@ MCTargetOptions::MCTargetOptions()
: 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 {
Modified: llvm/trunk/lib/Target/TargetMachine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/TargetMachine.cpp?rev=284160&r1=284159&r2=284160&view=diff
==============================================================================
--- llvm/trunk/lib/Target/TargetMachine.cpp (original)
+++ llvm/trunk/lib/Target/TargetMachine.cpp Thu Oct 13 15:54:39 2016
@@ -115,9 +115,6 @@ static TLSModel::Model getSelectedTLSMod
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 @@ bool TargetMachine::shouldAssumeDSOLocal
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;
}
Added: llvm/trunk/test/CodeGen/X86/global-access-pie-copyrelocs.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/global-access-pie-copyrelocs.ll?rev=284160&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/global-access-pie-copyrelocs.ll (added)
+++ llvm/trunk/test/CodeGen/X86/global-access-pie-copyrelocs.ll Thu Oct 13 15:54:39 2016
@@ -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
+ at 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 at 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
+ at 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 at 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
+ at 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 at 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.
+ at 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 at 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 at 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 $_GLOBAL_OFFSET_TABLE_{{.*}}, %ebx
+; X32-NEXT: movl foo at GOT(%ebx), %eax
+; X64-LABEL: my_access_fp_foo:
+; X64: movq foo at GOTPCREL(%rip), %rdi
+
+entry:
+ %call = call i32 @access_fp(i32 ()* @foo)
+ ret i32 %call
+}
+
+; LinkOnceODR Linkage, function pointer access.
+
+$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 at 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}
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