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Use MachineBranchProbabilityInfo in If-Conversion instead of its own heuristics.

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llvm-svn: 136826
This commit is contained in:
Jakub Staszak 2011-08-03 22:34:43 +00:00
parent fdea9930ac
commit 9d083611d4
5 changed files with 28 additions and 46 deletions
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37
lib/CodeGen/IfConversion.cpp
View File

@ -16,14 +16,13 @@
#include "llvm/Function.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/Codegen/MachineBranchProbabilityInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/MC/MCInstrItineraries.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
@ -154,7 +153,8 @@ namespace {
const TargetInstrInfo *TII;
const TargetRegisterInfo *TRI;
const InstrItineraryData *InstrItins;
const MachineLoopInfo *MLI;
const MachineBranchProbabilityInfo *MBPI;
bool MadeChange;
int FnNum;
public:
@ -162,9 +162,9 @@ namespace {
IfConverter() : MachineFunctionPass(ID), FnNum(-1) {
initializeIfConverterPass(*PassRegistry::getPassRegistry());
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<MachineLoopInfo>();
AU.addRequired<MachineBranchProbabilityInfo>();
MachineFunctionPass::getAnalysisUsage(AU);
}
@ -252,7 +252,7 @@ namespace {
}
INITIALIZE_PASS_BEGIN(IfConverter, "if-converter", "If Converter", false, false)
INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
INITIALIZE_PASS_END(IfConverter, "if-converter", "If Converter", false, false)
FunctionPass *llvm::createIfConverterPass() { return new IfConverter(); }
@ -261,7 +261,7 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
TLI = MF.getTarget().getTargetLowering();
TII = MF.getTarget().getInstrInfo();
TRI = MF.getTarget().getRegisterInfo();
MLI = &getAnalysis<MachineLoopInfo>();
MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
InstrItins = MF.getTarget().getInstrItineraryData();
if (!TII) return false;
@ -790,28 +790,9 @@ IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
bool TNeedSub = TrueBBI.Predicate.size() > 0;
bool FNeedSub = FalseBBI.Predicate.size() > 0;
bool Enqueued = false;
// Try to predict the branch, using loop info to guide us.
// General heuristics are:
// - backedge -> 90% taken
// - early exit -> 20% taken
// - branch predictor confidence -> 90%
BranchProbability Prediction(5, 10);
MachineLoop *Loop = MLI->getLoopFor(BB);
if (Loop) {
if (TrueBBI.BB == Loop->getHeader())
Prediction = BranchProbability(9, 10);
else if (FalseBBI.BB == Loop->getHeader())
Prediction = BranchProbability(1, 10);
MachineLoop *TrueLoop = MLI->getLoopFor(TrueBBI.BB);
MachineLoop *FalseLoop = MLI->getLoopFor(FalseBBI.BB);
if (!TrueLoop || TrueLoop->getParentLoop() == Loop)
Prediction = BranchProbability(2, 10);
else if (!FalseLoop || FalseLoop->getParentLoop() == Loop)
Prediction = BranchProbability(8, 10);
}
BranchProbability Prediction = MBPI->getEdgeProbability(BB, TrueBBI.BB);
if (CanRevCond && ValidDiamond(TrueBBI, FalseBBI, Dups, Dups2) &&
MeetIfcvtSizeLimit(*TrueBBI.BB, (TrueBBI.NonPredSize - (Dups + Dups2) +
TrueBBI.ExtraCost), TrueBBI.ExtraCost2,

10
test/CodeGen/ARM/ifcvt4.ll
View File

@ -1,8 +1,10 @@
; RUN: llc < %s -march=arm
; RUN: llc < %s -march=arm | grep subgt | count 1
; RUN: llc < %s -march=arm | grep suble | count 1
; FIXME: Check for # of unconditional branch after adding branch folding post ifcvt.
; RUN: llc < %s -march=arm | FileCheck %s
; Do not if-convert when branches go to the different loops.
; CHECK: _t:
; CHECK-NOT: subgt
; CHECK-NOT: suble
; Don't use
define i32 @t(i32 %a, i32 %b) {
entry:
%tmp1434 = icmp eq i32 %a, %b ; <i1> [#uses=1]

1
test/CodeGen/ARM/indirectbr.ll
View File

@ -22,7 +22,6 @@ bb2: ; preds = %entry, %bb3
%gotovar.4.0 = phi i8* [ %gotovar.4.0.pre, %bb3 ], [ %0, %entry ] ; <i8*> [#uses=1]
; ARM: bx
; THUMB: mov pc,
; THUMB2: mov pc,
indirectbr i8* %gotovar.4.0, [label %L5, label %L4, label %L3, label %L2, label %L1]
bb3: ; preds = %entry

18
test/CodeGen/Thumb2/2010-06-21-TailMergeBug.ll
View File

@ -32,15 +32,15 @@
define fastcc i32 @parse_percent_token() nounwind {
entry:
; CHECK: ittt eq
; CHECK: ittt eq
; CHECK: ittt eq
; CHECK: ittt eq
; CHECK: ittt eq
; CHECK: moveq r0
; CHECK-NOT: LBB0_
; CHECK: ldreq
; CHECK: popeq
; CHECK: pop
; CHECK: pop
; CHECK: pop
; CHECK: pop
; CHECK: pop
; CHECK: pop
; CHECK: pop
; Do not convert into single stream code. BranchProbability Analysis assumes
; that branches which goes to "ret" intruction have lower probabilities.
switch i32 undef, label %bb7 [
i32 37, label %bb43
i32 48, label %bb5

8
test/CodeGen/Thumb2/thumb2-ifcvt1.ll
View File

@ -21,13 +21,13 @@ cond_next:
ret i32 %tmp15
}
; FIXME: Check for # of unconditional branch after adding branch folding post ifcvt.
define i32 @t2(i32 %a, i32 %b) nounwind {
entry:
; Do not if-convert when branches go to the different loops.
; CHECK: t2:
; CHECK: ite gt
; CHECK: subgt
; CHECK: suble
; CHECK-NOT: ite gt
; CHECK-NOT: subgt
; CHECK-NOT: suble
%tmp1434 = icmp eq i32 %a, %b ; <i1> [#uses=1]
br i1 %tmp1434, label %bb17, label %bb.outer