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Teach if-converter to be more careful with predicating instructions that would

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take multiple cycles to decode.
For the current if-converter clients (actually only ARM), the instructions that
are predicated on false are not nops. They would still take machine cycles to
decode. Micro-coded instructions such as LDM / STM can potentially take multiple
cycles to decode. If-converter should take treat them as non-micro-coded
simple instructions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113570 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2010-09-10 01:29:16 +00:00
parent 920a2089d9
commit 3ef1c8759a
28 changed files with 160 additions and 80 deletions
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13
lib/CodeGen/IfConversion.cpp
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@ -18,6 +18,7 @@
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetInstrItineraries.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
@ -150,6 +151,7 @@ namespace {
const TargetLowering *TLI;
const TargetInstrInfo *TII;
const TargetRegisterInfo *TRI;
const InstrItineraryData *InstrItins;
bool MadeChange;
int FnNum;
public:
@ -238,6 +240,7 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
TLI = MF.getTarget().getTargetLowering();
TII = MF.getTarget().getInstrInfo();
TRI = MF.getTarget().getRegisterInfo();
InstrItins = MF.getTarget().getInstrItineraryData();
if (!TII) return false;
// Tail merge tend to expose more if-conversion opportunities.
@ -641,9 +644,10 @@ void IfConverter::ScanInstructions(BBInfo &BBI) {
bool isCondBr = BBI.IsBrAnalyzable && TID.isConditionalBranch();
if (!isCondBr) {
if (!isPredicated)
BBI.NonPredSize++;
else if (!AlreadyPredicated) {
if (!isPredicated) {
unsigned NumOps = TII->getNumMicroOps(&*I, InstrItins);
BBI.NonPredSize += NumOps;
} else if (!AlreadyPredicated) {
// FIXME: This instruction is already predicated before the
// if-conversion pass. It's probably something like a conditional move.
// Mark this block unpredicable for now.
@ -1364,7 +1368,8 @@ void IfConverter::CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI,
MachineInstr *MI = MF.CloneMachineInstr(I);
ToBBI.BB->insert(ToBBI.BB->end(), MI);
ToBBI.NonPredSize++;
unsigned NumOps = TII->getNumMicroOps(MI, InstrItins);
ToBBI.NonPredSize += NumOps;
if (!TII->isPredicated(I) && !MI->isDebugValue()) {
if (!TII->PredicateInstruction(MI, Cond)) {