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factor some logic out into a helper function, allow remat of loads from constant

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globals.  This implements remat-constant.ll even without aggressive-remat.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@74373 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-06-27 04:38:55 +00:00
parent 18c5987fa3
commit 74d3f50a80
2 changed files with 26 additions and 6 deletions
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29
lib/Target/X86/X86InstrInfo.cpp
View File

@ -18,6 +18,7 @@
#include "X86MachineFunctionInfo.h"
#include "X86Subtarget.h"
#include "X86TargetMachine.h"
#include "llvm/GlobalVariable.h"
#include "llvm/DerivedTypes.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/CodeGen/MachineConstantPool.h"
@ -28,7 +29,6 @@
#include "llvm/Support/CommandLine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetAsmInfo.h"
using namespace llvm;
namespace {
@ -782,6 +782,29 @@ static inline bool isGVStub(GlobalValue *GV, X86TargetMachine &TM) {
return TM.getSubtarget<X86Subtarget>().GVRequiresExtraLoad(GV, TM, false);
}
/// CanRematLoadWithDispOperand - Return true if a load with the specified
/// operand is a candidate for remat: for this to be true we need to know that
/// the load will always return the same value, even if moved.
static bool CanRematLoadWithDispOperand(const MachineOperand &MO,
X86TargetMachine &TM) {
// Loads from constant pool entries can be remat'd.
if (MO.isCPI()) return true;
// We can remat globals in some cases.
if (MO.isGlobal()) {
// If this is a load of a stub, not of the global, we can remat it. This
// access will always return the address of the global.
if (isGVStub(MO.getGlobal(), TM))
return true;
// If the global itself is constant, we can remat the load.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(MO.getGlobal()))
if (GV->isConstant())
return true;
}
return false;
}
bool
X86InstrInfo::isReallyTriviallyReMaterializable(const MachineInstr *MI) const {
switch (MI->getOpcode()) {
@ -802,9 +825,7 @@ X86InstrInfo::isReallyTriviallyReMaterializable(const MachineInstr *MI) const {
if (MI->getOperand(1).isReg() &&
MI->getOperand(2).isImm() &&
MI->getOperand(3).isReg() && MI->getOperand(3).getReg() == 0 &&
(MI->getOperand(4).isCPI() ||
(MI->getOperand(4).isGlobal() &&
isGVStub(MI->getOperand(4).getGlobal(), TM)))) {
CanRematLoadWithDispOperand(MI->getOperand(4), TM)) {
unsigned BaseReg = MI->getOperand(1).getReg();
if (BaseReg == 0 || BaseReg == X86::RIP)
return true;

3
test/CodeGen/X86/remat-constant.ll
View File

@ -1,5 +1,4 @@
; RUN: llvm-as < %s | llc -mtriple=x86_64-linux -relocation-model=static -aggressive-remat | grep xmm | count 2
; XFAIL: *
; RUN: llvm-as < %s | llc -mtriple=x86_64-linux -relocation-model=static | grep xmm | count 2
declare void @bar() nounwind