!2 = !{ i8 0, i8 2, i8 3, i8 6 }
!3 = !{ i8 -2, i8 0, i8 3, i8 6 }
+'``absolute_symbol``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+``absolute_symbol`` metadata may be attached to a global variable
+declaration. It marks the declaration as a reference to an absolute symbol,
+which causes the backend to use absolute relocations for the symbol even
+in position independent code, and expresses the possible ranges that the
+global variable's *address* (not its value) is in, in the same format as
+``range`` metadata.
+
+Example:
+
+.. code-block:: llvm
+
+ @a = external global i8, !absolute_symbol !0 ; Absolute symbol in range [0,256)
+
+ ...
+ !0 = !{ i64 0, i64 256 }
+
'``unpredictable``' Metadata
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
namespace llvm {
class Comdat;
+class ConstantRange;
class Error;
class GlobalObject;
class Module;
}
GlobalObject *getBaseObject();
+ /// Returns whether this is a reference to an absolute symbol.
+ bool isAbsoluteSymbolRef() const;
+
+ /// If this is an absolute symbol reference, returns the range of the symbol,
+ /// otherwise returns None.
+ Optional<ConstantRange> getAbsoluteSymbolRange() const;
+
/// This method unlinks 'this' from the containing module, but does not delete
/// it.
virtual void removeFromParent() = 0;
MD_loop = 18, // "llvm.loop"
MD_type = 19, // "type"
MD_section_prefix = 20, // "section_prefix"
+ MD_absolute_symbol = 21, // "absolute_symbol"
};
/// Known operand bundle tag IDs, which always have the same value. All
if (const Argument *A = dyn_cast<Argument>(V))
return A->hasByValOrInAllocaAttr() || A->hasNonNullAttr();
- // A global variable in address space 0 is non null unless extern weak.
- // Other address spaces may have null as a valid address for a global,
- // so we can't assume anything.
+ // A global variable in address space 0 is non null unless extern weak
+ // or an absolute symbol reference. Other address spaces may have null as a
+ // valid address for a global, so we can't assume anything.
if (const GlobalValue *GV = dyn_cast<GlobalValue>(V))
- return !GV->hasExternalWeakLinkage() &&
+ return !GV->isAbsoluteSymbolRef() && !GV->hasExternalWeakLinkage() &&
GV->getType()->getAddressSpace() == 0;
// A Load tagged with nonnull metadata is never null.
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Triple.h"
#include "llvm/IR/Constants.h"
+#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalValue.h"
return nullptr;
}
+bool GlobalValue::isAbsoluteSymbolRef() const {
+ auto *GO = dyn_cast<GlobalObject>(this);
+ if (!GO)
+ return false;
+
+ return GO->getMetadata(LLVMContext::MD_absolute_symbol);
+}
+
+Optional<ConstantRange> GlobalValue::getAbsoluteSymbolRange() const {
+ auto *GO = dyn_cast<GlobalObject>(this);
+ if (!GO)
+ return None;
+
+ MDNode *MD = GO->getMetadata(LLVMContext::MD_absolute_symbol);
+ if (!MD)
+ return None;
+
+ return getConstantRangeFromMetadata(*MD);
+}
+
//===----------------------------------------------------------------------===//
// GlobalVariable Implementation
//===----------------------------------------------------------------------===//
{MD_loop, "llvm.loop"},
{MD_type, "type"},
{MD_section_prefix, "section_prefix"},
+ {MD_absolute_symbol, "absolute_symbol"},
};
for (auto &MDKind : MDKinds) {
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SelectionDAGISel.h"
+#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
return false;
Imm = N;
- return TM.getCodeModel() == CodeModel::Small;
+ if (N->getOpcode() != ISD::TargetGlobalAddress)
+ return TM.getCodeModel() == CodeModel::Small;
+
+ Optional<ConstantRange> CR =
+ cast<GlobalAddressSDNode>(N)->getGlobal()->getAbsoluteSymbolRange();
+ if (!CR)
+ return TM.getCodeModel() == CodeModel::Small;
+
+ return CR->getUnsignedMax().ult(1ull << 32);
}
bool X86DAGToDAGISel::selectLEA64_32Addr(SDValue N, SDValue &Base,
return true;
}
+ // Keep track of the original value type and whether this value was
+ // truncated. If we see a truncation from pointer type to VT that truncates
+ // bits that are known to be zero, we can use a narrow reference.
+ EVT VT = N.getValueType();
+ bool WasTruncated = false;
+ if (N.getOpcode() == ISD::TRUNCATE) {
+ WasTruncated = true;
+ N = N.getOperand(0);
+ }
+
if (N.getOpcode() != X86ISD::Wrapper)
return false;
- Op = N.getOperand(0);
+ // We can only use non-GlobalValues as immediates if they were not truncated,
+ // as we do not have any range information. If we have a GlobalValue and the
+ // address was not truncated, we can select it as an operand directly.
+ unsigned Opc = N.getOperand(0)->getOpcode();
+ if (Opc != ISD::TargetGlobalAddress || !WasTruncated) {
+ Op = N.getOperand(0);
+ // We can only select the operand directly if we didn't have to look past a
+ // truncate.
+ return !WasTruncated;
+ }
+
+ // Check that the global's range fits into VT.
+ auto *GA = cast<GlobalAddressSDNode>(N.getOperand(0));
+ Optional<ConstantRange> CR = GA->getGlobal()->getAbsoluteSymbolRange();
+ if (!CR || CR->getUnsignedMax().uge(1ull << VT.getSizeInBits()))
+ return false;
+
+ // Okay, we can use a narrow reference.
+ Op = CurDAG->getTargetGlobalAddress(GA->getGlobal(), SDLoc(N), VT,
+ GA->getOffset(), GA->getTargetFlags());
return true;
}
}
// Returns the appropriate wrapper opcode for a global reference.
-unsigned X86TargetLowering::getGlobalWrapperKind() const {
+unsigned X86TargetLowering::getGlobalWrapperKind(const GlobalValue *GV) const {
+ // References to absolute symbols are never PC-relative.
+ if (GV && GV->isAbsoluteSymbolRef())
+ return X86ISD::Wrapper;
+
CodeModel::Model M = getTargetMachine().getCodeModel();
if (Subtarget.isPICStyleRIPRel() &&
(M == CodeModel::Small || M == CodeModel::Kernel))
Result = DAG.getTargetGlobalAddress(GV, dl, PtrVT, 0, OpFlags);
}
- Result = DAG.getNode(getGlobalWrapperKind(), dl, PtrVT, Result);
+ Result = DAG.getNode(getGlobalWrapperKind(GV), dl, PtrVT, Result);
// With PIC, the address is actually $g + Offset.
if (isGlobalRelativeToPICBase(OpFlags)) {
SDValue InsertBitToMaskVector(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerINSERT_VECTOR_ELT(SDValue Op, SelectionDAG &DAG) const;
- unsigned getGlobalWrapperKind() const;
+ unsigned getGlobalWrapperKind(const GlobalValue *GV = nullptr) const;
SDValue LowerConstantPool(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerBlockAddress(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerGlobalAddress(const GlobalValue *GV, const SDLoc &dl,
// Eventually, it would be nice to allow ConstantHoisting to merge constants
// globally for potentially added savings.
//
-def imm8_su : PatLeaf<(i8 imm), [{
+def imm8_su : PatLeaf<(i8 relocImm), [{
return !shouldAvoidImmediateInstFormsForSize(N);
}]>;
-def imm16_su : PatLeaf<(i16 imm), [{
+def imm16_su : PatLeaf<(i16 relocImm), [{
return !shouldAvoidImmediateInstFormsForSize(N);
}]>;
def imm32_su : PatLeaf<(i32 relocImm), [{
def ROR8ri : Ii8<0xC0, MRM1r, (outs GR8 :$dst), (ins GR8 :$src1, u8imm:$src2),
"ror{b}\t{$src2, $dst|$dst, $src2}",
- [(set GR8:$dst, (rotr GR8:$src1, (i8 imm:$src2)))], IIC_SR>;
+ [(set GR8:$dst, (rotr GR8:$src1, (i8 relocImm:$src2)))],
+ IIC_SR>;
def ROR16ri : Ii8<0xC1, MRM1r, (outs GR16:$dst), (ins GR16:$src1, u8imm:$src2),
"ror{w}\t{$src2, $dst|$dst, $src2}",
- [(set GR16:$dst, (rotr GR16:$src1, (i8 imm:$src2)))],
+ [(set GR16:$dst, (rotr GR16:$src1, (i8 relocImm:$src2)))],
IIC_SR>, OpSize16;
def ROR32ri : Ii8<0xC1, MRM1r, (outs GR32:$dst), (ins GR32:$src1, u8imm:$src2),
"ror{l}\t{$src2, $dst|$dst, $src2}",
- [(set GR32:$dst, (rotr GR32:$src1, (i8 imm:$src2)))],
+ [(set GR32:$dst, (rotr GR32:$src1, (i8 relocImm:$src2)))],
IIC_SR>, OpSize32;
def ROR64ri : RIi8<0xC1, MRM1r, (outs GR64:$dst),
(ins GR64:$src1, u8imm:$src2),
"ror{q}\t{$src2, $dst|$dst, $src2}",
- [(set GR64:$dst, (rotr GR64:$src1, (i8 imm:$src2)))],
+ [(set GR64:$dst, (rotr GR64:$src1, (i8 relocImm:$src2)))],
IIC_SR>;
// Rotate by 1
if (TM.getCodeModel() == CodeModel::Large)
return X86II::MO_NO_FLAG;
+ // Absolute symbols can be referenced directly.
+ if (GV && GV->isAbsoluteSymbolRef())
+ return X86II::MO_NO_FLAG;
+
if (TM.shouldAssumeDSOLocal(M, GV))
return classifyLocalReference(GV);
--- /dev/null
+; RUN: llc < %s | FileCheck %s
+; RUN: llc -relocation-model=pic < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@bit_mask8 = external hidden global i8, !absolute_symbol !0
+@bit_mask32 = external hidden global i8, !absolute_symbol !1
+@bit_mask64 = external hidden global i8, !absolute_symbol !2
+
+declare void @f()
+
+define void @foo8(i8* %ptr) {
+ %load = load i8, i8* %ptr
+ ; CHECK: testb $bit_mask8, (%rdi)
+ %and = and i8 %load, ptrtoint (i8* @bit_mask8 to i8)
+ %icmp = icmp eq i8 %and, 0
+ br i1 %icmp, label %t, label %f
+
+t:
+ call void @f()
+ ret void
+
+f:
+ ret void
+}
+
+define void @foo32(i32* %ptr) {
+ %load = load i32, i32* %ptr
+ ; CHECK: testl $bit_mask32, (%rdi)
+ %and = and i32 %load, ptrtoint (i8* @bit_mask32 to i32)
+ %icmp = icmp eq i32 %and, 0
+ br i1 %icmp, label %t, label %f
+
+t:
+ call void @f()
+ ret void
+
+f:
+ ret void
+}
+
+define void @foo64(i64* %ptr) {
+ %load = load i64, i64* %ptr
+ ; CHECK: movabsq $bit_mask64, %rax
+ ; CHECK: testq (%rdi), %rax
+ %and = and i64 %load, ptrtoint (i8* @bit_mask64 to i64)
+ %icmp = icmp eq i64 %and, 0
+ br i1 %icmp, label %t, label %f
+
+t:
+ call void @f()
+ ret void
+
+f:
+ ret void
+}
+
+!0 = !{i64 0, i64 256}
+!1 = !{i64 0, i64 4294967296}
+!2 = !{i64 -1, i64 -1}
--- /dev/null
+; RUN: llc < %s | FileCheck %s
+; RUN: llc -relocation-model=pic < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@bit_mask8 = external hidden global i8, !absolute_symbol !0
+@bit_mask32 = external hidden global i8, !absolute_symbol !1
+@bit_mask64 = external hidden global i8, !absolute_symbol !2
+
+declare void @f()
+
+define void @foo32(i32* %ptr) {
+ %load = load i32, i32* %ptr
+ %and = and i32 %load, 31
+ %shl = shl i32 1, %and
+ %and2 = and i32 %shl, ptrtoint (i8* @bit_mask32 to i32)
+ ; CHECK: movl $bit_mask32, %eax
+ ; CHECK: btl %ecx, %eax
+ %icmp = icmp eq i32 %and2, 0
+ br i1 %icmp, label %t, label %f
+
+t:
+ call void @f()
+ ret void
+
+f:
+ ret void
+}
+
+define void @foo64(i64* %ptr) {
+ %load = load i64, i64* %ptr
+ %and = and i64 %load, 63
+ %shl = shl i64 1, %and
+ %and2 = and i64 %shl, ptrtoint (i8* @bit_mask64 to i64)
+ ; CHECK: movabsq $bit_mask64, %rax
+ ; CHECK: btq %rcx, %rax
+ %icmp = icmp eq i64 %and2, 0
+ br i1 %icmp, label %t, label %f
+
+t:
+ call void @f()
+ ret void
+
+f:
+ ret void
+}
+
+!0 = !{i64 0, i64 256}
+!1 = !{i64 0, i64 4294967296}
+!2 = !{i64 -1, i64 -1}
--- /dev/null
+; RUN: llc < %s | FileCheck %s
+; RUN: llc -relocation-model=pic < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@foo = external global i8, align 1, !absolute_symbol !0
+
+define void @bar(i8* %x) {
+entry:
+ %0 = load i8, i8* %x, align 1
+ %conv = sext i8 %0 to i32
+ ; CHECK: testb $foo, (%rdi)
+ %and = and i32 %conv, sext (i8 ptrtoint (i8* @foo to i8) to i32)
+ %tobool = icmp eq i32 %and, 0
+ br i1 %tobool, label %if.end, label %if.then
+
+if.then: ; preds = %entry
+ tail call void (...) @xf()
+ br label %if.end
+
+if.end: ; preds = %entry, %if.then
+ ret void
+}
+
+declare void @xf(...)
+
+!0 = !{i32 0, i32 256}
--- /dev/null
+; RUN: llc < %s | FileCheck %s
+; RUN: llc -relocation-model=pic < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@align = external hidden global i8, !absolute_symbol !0
+
+declare void @f()
+
+define void @foo(i64 %val) {
+ %shr = lshr i64 %val, zext (i8 ptrtoint (i8* @align to i8) to i64)
+ %shl = shl i64 %val, zext (i8 sub (i8 64, i8 ptrtoint (i8* @align to i8)) to i64)
+ ; CHECK: rorq $align, %rdi
+ %ror = or i64 %shr, %shl
+ %cmp = icmp ult i64 %ror, 109
+ br i1 %cmp, label %t, label %f
+
+t:
+ call void @f()
+ ret void
+
+f:
+ ret void
+}
+
+!0 = !{i64 0, i64 256}
--- /dev/null
+; RUN: opt -S -functionattrs %s | FileCheck %s
+
+@a = external global i8, !absolute_symbol !0
+
+; CHECK-NOT: define nonnull
+define i8* @foo() {
+ ret i8* @a
+}
+
+!0 = !{i64 0, i64 256}