From aceb767487527b16c868229d26a86b01af9a0d36 Mon Sep 17 00:00:00 2001 From: Eric Christopher Date: Mon, 4 May 2020 13:48:56 -0700 Subject: [PATCH] Fix full unrolling with new pass manager. Last we looked at this and couldn't come up with a reason to change it, but with a pragma for full loop unrolling we bypass every other loop unroll and then fail to fully unroll a loop when the pragma is set. Move the OnlyWhenForced out of the check and into the initialization of the full unroll pass in the new pass manager. This doesn't show up with the old pass manager. Add a new option to opt so that we can turn off loop unrolling manually since this is a difference between clang and opt. Tested with check-clang and check-llvm. --- lib/Passes/PassBuilder.cpp | 11 ++-- test/Transforms/LoopUnroll/FullUnroll.ll | 77 ++++++++++++++++++++++++ tools/opt/NewPMDriver.cpp | 9 +++ 3 files changed, 92 insertions(+), 5 deletions(-) create mode 100644 test/Transforms/LoopUnroll/FullUnroll.ll diff --git a/lib/Passes/PassBuilder.cpp b/lib/Passes/PassBuilder.cpp index 1b1701cbe26..fda2af7e80b 100644 --- a/lib/Passes/PassBuilder.cpp +++ b/lib/Passes/PassBuilder.cpp @@ -519,12 +519,13 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level, LPM2.addPass(LoopDeletionPass()); // Do not enable unrolling in PreLinkThinLTO phase during sample PGO // because it changes IR to makes profile annotation in back compile - // inaccurate. - if ((Phase != ThinLTOPhase::PreLink || !PGOOpt || - PGOOpt->Action != PGOOptions::SampleUse) && - PTO.LoopUnrolling) + // inaccurate. The normal unroller doesn't pay attention to forced full unroll + // attributes so we need to make sure and allow the full unroll pass to pay + // attention to it. + if (Phase != ThinLTOPhase::PreLink || !PGOOpt || + PGOOpt->Action != PGOOptions::SampleUse) LPM2.addPass(LoopFullUnrollPass(Level.getSpeedupLevel(), - /*OnlyWhenForced=*/false, + /* OnlyWhenForced= */ !PTO.LoopUnrolling, PTO.ForgetAllSCEVInLoopUnroll)); for (auto &C : LoopOptimizerEndEPCallbacks) diff --git a/test/Transforms/LoopUnroll/FullUnroll.ll b/test/Transforms/LoopUnroll/FullUnroll.ll new file mode 100644 index 00000000000..01936e48768 --- /dev/null +++ b/test/Transforms/LoopUnroll/FullUnroll.ll @@ -0,0 +1,77 @@ +; RUN: opt -passes='default' -disable-verify --mtriple x86_64-pc-linux-gnu -new-pm-disable-loop-unrolling=true \ +; RUN: -S -o - %s | FileCheck %s + +; This checks that the loop full unroller will fire in the new pass manager +; when forced via #pragma in the source (or annotation in the code). +target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-unknown-linux-gnu" + +; We don't end up deleting the loop, merely turning it infinite, but we remove +; everything inside of it so check for the loop structure and absence of +; conditional branches. +; CHECK-LABEL: bb +; CHECK: br label +; CHECK-NOT: br i1 +; CHECK: br label +; CHECK-NOT: br i1 + +; Function Attrs: noinline nounwind optnone uwtable +define void @foo() #0 { +bb: + %tmp = alloca [5 x i32*], align 16 + %tmp1 = alloca i32, align 4 + %tmp2 = alloca i32, align 4 + store i32 5, i32* %tmp1, align 4 + br label %bb3 + +bb3: ; preds = %bb23, %bb + %tmp4 = load i32, i32* %tmp1, align 4 + %tmp5 = icmp ne i32 %tmp4, 0 + br i1 %tmp5, label %bb6, label %bb24 + +bb6: ; preds = %bb3 + store i32 0, i32* %tmp2, align 4 + br label %bb7 + +bb7: ; preds = %bb20, %bb6 + %tmp8 = load i32, i32* %tmp2, align 4 + %tmp9 = icmp slt i32 %tmp8, 5 + br i1 %tmp9, label %bb10, label %bb23 + +bb10: ; preds = %bb7 + %tmp11 = load i32, i32* %tmp2, align 4 + %tmp12 = sext i32 %tmp11 to i64 + %tmp13 = getelementptr inbounds [5 x i32*], [5 x i32*]* %tmp, i64 0, i64 %tmp12 + %tmp14 = load i32*, i32** %tmp13, align 8 + %tmp15 = icmp ne i32* %tmp14, null + br i1 %tmp15, label %bb16, label %bb19 + +bb16: ; preds = %bb10 + %tmp17 = load i32, i32* %tmp1, align 4 + %tmp18 = add nsw i32 %tmp17, -1 + store i32 %tmp18, i32* %tmp1, align 4 + br label %bb19 + +bb19: ; preds = %bb16, %bb10 + br label %bb20 + +bb20: ; preds = %bb19 + %tmp21 = load i32, i32* %tmp2, align 4 + %tmp22 = add nsw i32 %tmp21, 1 + store i32 %tmp22, i32* %tmp2, align 4 + br label %bb7, !llvm.loop !1 + +bb23: ; preds = %bb7 + br label %bb3 + +bb24: ; preds = %bb3 + ret void +} + +attributes #0 = { noinline nounwind optnone uwtable } + +!llvm.module.flags = !{!0} + +!0 = !{i32 1, !"wchar_size", i32 4} +!1 = distinct !{!1, !2} +!2 = !{!"llvm.loop.unroll.full"} diff --git a/tools/opt/NewPMDriver.cpp b/tools/opt/NewPMDriver.cpp index c99ad2f7b4d..ce86c3d6158 100644 --- a/tools/opt/NewPMDriver.cpp +++ b/tools/opt/NewPMDriver.cpp @@ -100,6 +100,11 @@ static cl::opt OptimizerLastEPPipeline( "the OptimizerLast extension point into default pipelines"), cl::Hidden); +// Individual pipeline tuning options. +static cl::opt DisableLoopUnrolling( + "new-pm-disable-loop-unrolling", + cl::desc("Disable loop unrolling in all relevant passes"), cl::init(false)); + extern cl::opt PGOKindFlag; extern cl::opt ProfileFile; extern cl::opt CSPGOKindFlag; @@ -260,6 +265,10 @@ bool llvm::runPassPipeline(StringRef Arg0, Module &M, TargetMachine *TM, SI.registerCallbacks(PIC); PipelineTuningOptions PTO; + // LoopUnrolling defaults on to true and DisableLoopUnrolling is initialized + // to false above so we shouldn't necessarily need to check whether or not the + // option has been enabled. + PTO.LoopUnrolling = !DisableLoopUnrolling; PTO.Coroutines = Coroutines; PassBuilder PB(TM, PTO, P, &PIC); registerEPCallbacks(PB, VerifyEachPass, DebugPM);