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[MemorySSA] Pass (for update) MSSAU when hoisting instructions. 

Summary: Pass MSSAU to makeLoopInvariant in order to properly update MSSA.

Reviewers: george.burgess.iv

Subscribers: Prazek, sanjoy.google, uabelho, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67470

llvm-svn: 371748
This commit is contained in:
Alina Sbirlea 2019-09-12 17:12:51 +00:00
parent e0cab70718
commit 6943472d45
2 changed files with 54 additions and 19 deletions
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47
llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
View File

@ -420,7 +420,8 @@ enum OperatorChain {
/// cost of creating an entirely new loop.
static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed,
OperatorChain &ParentChain,
DenseMap<Value *, Value *> &Cache) {
DenseMap<Value *, Value *> &Cache,
MemorySSAUpdater *MSSAU) {
auto CacheIt = Cache.find(Cond);
if (CacheIt != Cache.end())
return CacheIt->second;
@ -438,7 +439,7 @@ static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed,
// TODO: Handle: br (VARIANT|INVARIANT).
// Hoist simple values out.
if (L->makeLoopInvariant(Cond, Changed)) {
if (L->makeLoopInvariant(Cond, Changed, nullptr, MSSAU)) {
Cache[Cond] = Cond;
return Cond;
}
@ -478,7 +479,7 @@ static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed,
// which will cause the branch to go away in one loop and the condition to
// simplify in the other one.
if (Value *LHS = FindLIVLoopCondition(BO->getOperand(0), L, Changed,
ParentChain, Cache)) {
ParentChain, Cache, MSSAU)) {
Cache[Cond] = LHS;
return LHS;
}
@ -486,7 +487,7 @@ static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed,
// operand(1).
ParentChain = NewChain;
if (Value *RHS = FindLIVLoopCondition(BO->getOperand(1), L, Changed,
ParentChain, Cache)) {
ParentChain, Cache, MSSAU)) {
Cache[Cond] = RHS;
return RHS;
}
@ -500,12 +501,12 @@ static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed,
/// Cond is a condition that occurs in L. If it is invariant in the loop, or has
/// an invariant piece, return the invariant along with the operator chain type.
/// Otherwise, return null.
static std::pair<Value *, OperatorChain> FindLIVLoopCondition(Value *Cond,
Loop *L,
bool &Changed) {
static std::pair<Value *, OperatorChain>
FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed,
MemorySSAUpdater *MSSAU) {
DenseMap<Value *, Value *> Cache;
OperatorChain OpChain = OC_OpChainNone;
Value *FCond = FindLIVLoopCondition(Cond, L, Changed, OpChain, Cache);
Value *FCond = FindLIVLoopCondition(Cond, L, Changed, OpChain, Cache, MSSAU);
// In case we do find a LIV, it can not be obtained by walking up a mixed
// operator chain.
@ -694,8 +695,9 @@ bool LoopUnswitch::processCurrentLoop() {
}
for (IntrinsicInst *Guard : Guards) {
Value *LoopCond =
FindLIVLoopCondition(Guard->getOperand(0), currentLoop, Changed).first;
Value *LoopCond = FindLIVLoopCondition(Guard->getOperand(0), currentLoop,
Changed, MSSAU.get())
.first;
if (LoopCond &&
UnswitchIfProfitable(LoopCond, ConstantInt::getTrue(Context))) {
// NB! Unswitching (if successful) could have erased some of the
@ -735,8 +737,9 @@ bool LoopUnswitch::processCurrentLoop() {
if (BI->isConditional()) {
// See if this, or some part of it, is loop invariant. If so, we can
// unswitch on it if we desire.
Value *LoopCond = FindLIVLoopCondition(BI->getCondition(),
currentLoop, Changed).first;
Value *LoopCond = FindLIVLoopCondition(BI->getCondition(), currentLoop,
Changed, MSSAU.get())
.first;
if (LoopCond && !EqualityPropUnSafe(*LoopCond) &&
UnswitchIfProfitable(LoopCond, ConstantInt::getTrue(Context), TI)) {
++NumBranches;
@ -748,7 +751,7 @@ bool LoopUnswitch::processCurrentLoop() {
Value *LoopCond;
OperatorChain OpChain;
std::tie(LoopCond, OpChain) =
FindLIVLoopCondition(SC, currentLoop, Changed);
FindLIVLoopCondition(SC, currentLoop, Changed, MSSAU.get());
unsigned NumCases = SI->getNumCases();
if (LoopCond && NumCases) {
@ -808,8 +811,9 @@ bool LoopUnswitch::processCurrentLoop() {
for (BasicBlock::iterator BBI = (*I)->begin(), E = (*I)->end();
BBI != E; ++BBI)
if (SelectInst *SI = dyn_cast<SelectInst>(BBI)) {
Value *LoopCond = FindLIVLoopCondition(SI->getCondition(),
currentLoop, Changed).first;
Value *LoopCond = FindLIVLoopCondition(SI->getCondition(), currentLoop,
Changed, MSSAU.get())
.first;
if (LoopCond && UnswitchIfProfitable(LoopCond,
ConstantInt::getTrue(Context))) {
++NumSelects;
@ -1123,8 +1127,9 @@ bool LoopUnswitch::TryTrivialLoopUnswitch(bool &Changed) {
if (!BI->isConditional())
return false;
Value *LoopCond = FindLIVLoopCondition(BI->getCondition(),
currentLoop, Changed).first;
Value *LoopCond = FindLIVLoopCondition(BI->getCondition(), currentLoop,
Changed, MSSAU.get())
.first;
// Unswitch only if the trivial condition itself is an LIV (not
// partial LIV which could occur in and/or)
@ -1157,8 +1162,9 @@ bool LoopUnswitch::TryTrivialLoopUnswitch(bool &Changed) {
return true;
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurrentTerm)) {
// If this isn't switching on an invariant condition, we can't unswitch it.
Value *LoopCond = FindLIVLoopCondition(SI->getCondition(),
currentLoop, Changed).first;
Value *LoopCond = FindLIVLoopCondition(SI->getCondition(), currentLoop,
Changed, MSSAU.get())
.first;
// Unswitch only if the trivial condition itself is an LIV (not
// partial LIV which could occur in and/or)
@ -1240,6 +1246,9 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
LoopBlocks.clear();
NewBlocks.clear();
if (MSSAU && VerifyMemorySSA)
MSSA->verifyMemorySSA();
// First step, split the preheader and exit blocks, and add these blocks to
// the LoopBlocks list.
BasicBlock *NewPreheader =

26
llvm/test/Analysis/MemorySSA/loop-unswitch.ll Normal file
View File

@ -0,0 +1,26 @@
; RUN: opt -S -loop-unswitch -disable-basicaa -enable-mssa-loop-dependency -verify-memoryssa < %s | FileCheck %s
; REQUIRES: asserts
target triple = "x86_64-unknown-linux-gnu"
; CHECK-LABEL: @foo()
; Function Attrs: readnone speculatable
declare i32 @foo() #0
define void @main() {
entry:
br label %for.cond2682
for.cond2682: ; preds = %if.then2712, %entry
%mul2708 = call i32 @foo()
%tobool2709 = icmp ne i32 %mul2708, 0
br i1 %tobool2709, label %if.then2712, label %lor.lhs.false2710
lor.lhs.false2710: ; preds = %for.cond2682
unreachable
if.then2712: ; preds = %for.cond2682
br label %for.cond2682
}
attributes #0 = { readnone speculatable }