[SCEV] Add option to forget everything in SCEV.
Summary:
Create a method to forget everything in SCEV.
Add a cl::opt and PassManagerBuilder option to use this in LoopUnroll.
Motivation: Certain Halide applications spend a very long time compiling in forgetLoop, and prefer to forget everything and rebuild SCEV from scratch.
Sample difference in compile time reduction: 21.04 to 14.78 using current ToT release build.
Testcase showcasing this cannot be opensourced and is fairly large.
The option disabled by default, but it may be desirable to enable by
default. Evidence in favor (two difference runs on different days/ToT state):
File Before (s) After (s)
clang-9.bc 7267.91 6639.14
llvm-as.bc 194.12 194.12
llvm-dis.bc 62.50 62.50
opt.bc 1855.85 1857.53
File Before (s) After (s)
clang-9.bc 8588.70 7812.83
llvm-as.bc 196.20 194.78
llvm-dis.bc 61.55 61.97
opt.bc 1739.78 1886.26
Reviewers: sanjoy
Subscribers: mehdi_amini, jlebar, zzheng, javed.absar, dmgreen, jdoerfert, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60144
llvm-svn: 358304
diff --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index 0d62a81..fa8a0ab 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -335,8 +335,9 @@
Loop *L, unsigned Count, unsigned TripCount, bool Force, bool AllowRuntime,
bool AllowExpensiveTripCount, bool PreserveCondBr, bool PreserveOnlyFirst,
unsigned TripMultiple, unsigned PeelCount, bool UnrollRemainder,
- LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT, AssumptionCache *AC,
- OptimizationRemarkEmitter *ORE, bool PreserveLCSSA, Loop **RemainderLoop) {
+ bool ForgetAllSCEV, LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT,
+ AssumptionCache *AC, OptimizationRemarkEmitter *ORE, bool PreserveLCSSA,
+ Loop **RemainderLoop) {
BasicBlock *Preheader = L->getLoopPreheader();
if (!Preheader) {
@@ -469,8 +470,9 @@
if (RuntimeTripCount && TripMultiple % Count != 0 &&
!UnrollRuntimeLoopRemainder(L, Count, AllowExpensiveTripCount,
- EpilogProfitability, UnrollRemainder, LI, SE,
- DT, AC, PreserveLCSSA, RemainderLoop)) {
+ EpilogProfitability, UnrollRemainder,
+ ForgetAllSCEV, LI, SE, DT, AC, PreserveLCSSA,
+ RemainderLoop)) {
if (Force)
RuntimeTripCount = false;
else {
@@ -554,8 +556,12 @@
// and if something changes inside them then any of outer loops may also
// change. When we forget outermost loop, we also forget all contained loops
// and this is what we need here.
- if (SE)
- SE->forgetTopmostLoop(L);
+ if (SE) {
+ if (ForgetAllSCEV)
+ SE->forgetAllLoops();
+ else
+ SE->forgetTopmostLoop(L);
+ }
bool ContinueOnTrue = L->contains(BI->getSuccessor(0));
BasicBlock *LoopExit = BI->getSuccessor(ContinueOnTrue);
diff --git a/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp b/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp
index d5ccadd..a53ee9d 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp
@@ -197,8 +197,8 @@
if (TripMultiple == 1 || TripMultiple % Count != 0) {
if (!UnrollRuntimeLoopRemainder(L, Count, /*AllowExpensiveTripCount*/ false,
/*UseEpilogRemainder*/ true,
- UnrollRemainder, LI, SE, DT, AC, true,
- EpilogueLoop)) {
+ UnrollRemainder, /*ForgetAllSCEV*/ false,
+ LI, SE, DT, AC, true, EpilogueLoop)) {
LLVM_DEBUG(dbgs() << "Won't unroll-and-jam; remainder loop could not be "
"generated when assuming runtime trip count\n");
return LoopUnrollResult::Unmodified;
diff --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index 2f1a759..20d687f 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -553,10 +553,10 @@
bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
bool AllowExpensiveTripCount,
bool UseEpilogRemainder,
- bool UnrollRemainder, LoopInfo *LI,
- ScalarEvolution *SE, DominatorTree *DT,
- AssumptionCache *AC, bool PreserveLCSSA,
- Loop **ResultLoop) {
+ bool UnrollRemainder, bool ForgetAllSCEV,
+ LoopInfo *LI, ScalarEvolution *SE,
+ DominatorTree *DT, AssumptionCache *AC,
+ bool PreserveLCSSA, Loop **ResultLoop) {
LLVM_DEBUG(dbgs() << "Trying runtime unrolling on Loop: \n");
LLVM_DEBUG(L->dump());
LLVM_DEBUG(UseEpilogRemainder ? dbgs() << "Using epilog remainder.\n"
@@ -953,8 +953,8 @@
/*Force*/ false, /*AllowRuntime*/ false,
/*AllowExpensiveTripCount*/ false, /*PreserveCondBr*/ true,
/*PreserveOnlyFirst*/ false, /*TripMultiple*/ 1,
- /*PeelCount*/ 0, /*UnrollRemainder*/ false, LI, SE, DT, AC,
- /*ORE*/ nullptr, PreserveLCSSA);
+ /*PeelCount*/ 0, /*UnrollRemainder*/ false, ForgetAllSCEV,
+ LI, SE, DT, AC, /*ORE*/ nullptr, PreserveLCSSA);
}
if (ResultLoop && UnrollResult != LoopUnrollResult::FullyUnrolled)