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In the new pass manager use PTO.LoopUnrolling to determine when and how

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we will unroll loops. Also comment a few occasions where we need to
know whether or not we're forcing the unwinder or not.

The default before and after this patch is for LoopUnroll to be enabled,
and for it to use a cost model to determine whether to unroll the loop
(`OnlyWhenForced = false`). Before this patch, disabling loop unroll
would not run the LoopUnroll pass. After this patch, the LoopUnroll pass
is being run, but it restricts unrolling to only the loops marked by a
pragma (`OnlyWhenForced = true`).

In addition, this patch disables the UnrollAndJam pass when disabling unrolling.

Testcase is in clang because it's controlling how the loop optimizer
is being set up and there's no other way to trigger the behavior.

llvm-svn: 374838
This commit is contained in:
Eric Christopher 2019-10-14 22:56:07 +00:00
parent 72593d3bdc
commit c3649a0871
2 changed files with 18 additions and 6 deletions
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12
clang/test/Misc/loop-opt-setup.c Normal file
View File

@ -0,0 +1,12 @@
// RUN: %clang -O1 -fexperimental-new-pass-manager -fno-unroll-loops -S -o - %s -emit-llvm | FileCheck %s
// RUN: %clang -O1 -fno-unroll-loops -S -o - %s -emit-llvm | FileCheck %s
extern int a[16];
int b = 0;
int foo(void) {
#pragma unroll
for (int i = 0; i < 16; ++i)
a[i] = b += 2;
return b;
}
// CHECK-NOT: br i1

12
llvm/lib/Passes/PassBuilder.cpp
View File

@ -471,8 +471,8 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
if ((Phase != ThinLTOPhase::PreLink || !PGOOpt ||
PGOOpt->Action != PGOOptions::SampleUse) &&
PTO.LoopUnrolling)
LPM2.addPass(
LoopFullUnrollPass(Level, false, PTO.ForgetAllSCEVInLoopUnroll));
LPM2.addPass(LoopFullUnrollPass(Level, /*OnlyWhenForced=*/false,
PTO.ForgetAllSCEVInLoopUnroll));
for (auto &C : LoopOptimizerEndEPCallbacks)
C(LPM2, Level);
@ -953,13 +953,13 @@ ModulePassManager PassBuilder::buildModuleOptimizationPipeline(
// combiner for cleanup here so that the unrolling and LICM can be pipelined
// across the loop nests.
// We do UnrollAndJam in a separate LPM to ensure it happens before unroll
if (EnableUnrollAndJam) {
if (EnableUnrollAndJam && PTO.LoopUnrolling) {
OptimizePM.addPass(
createFunctionToLoopPassAdaptor(LoopUnrollAndJamPass(Level)));
}
if (PTO.LoopUnrolling)
OptimizePM.addPass(LoopUnrollPass(
LoopUnrollOptions(Level, false, PTO.ForgetAllSCEVInLoopUnroll)));
OptimizePM.addPass(LoopUnrollPass(
LoopUnrollOptions(Level, /*OnlyWhenForced=*/!PTO.LoopUnrolling,
PTO.ForgetAllSCEVInLoopUnroll)));
OptimizePM.addPass(WarnMissedTransformationsPass());
OptimizePM.addPass(InstCombinePass());
OptimizePM.addPass(RequireAnalysisPass<OptimizationRemarkEmitterAnalysis, Function>());