[LDist] Match behavior between invoking via optimization pipeline or opt -loop-distribute

In r267672, where the loop distribution pragma was introduced, I tried
it hard to keep the old behavior for opt: when opt is invoked
with -loop-distribute, it should distribute the loop (it's off by
default when ran via the optimization pipeline).

As MichaelZ has discovered this has the unintended consequence of
breaking a very common developer work-flow to reproduce compilations
using opt: First you print the pass pipeline of clang
with -debug-pass=Arguments and then invoking opt with the returned
arguments.

clang -debug-pass will include -loop-distribute but the pass is invoked
with default=off so nothing happens unless the loop carries the pragma.
While through opt (default=on) we will try to distribute all loops.

This changes opt's default to off as well to match clang.  The tests are
modified to explicitly enable the transformation.

llvm-svn: 290235

include/llvm/Transforms/Scalar.h

@@ -500,10 +500,7 @@ FunctionPass *createNaryReassociatePass();
 //
 // LoopDistribute - Distribute loops.
 //
-// ProcessAllLoopsByDefault instructs the pass to look for distribution
+FunctionPass *createLoopDistributePass();
-// opportunities in all loops unless -enable-loop-distribute or the
-// llvm.loop.distribute.enable metadata data override this default.
-FunctionPass *createLoopDistributePass(bool ProcessAllLoopsByDefault);
 
 //===----------------------------------------------------------------------===//
 //

lib/Transforms/IPO/PassManagerBuilder.cpp

@@ -561,7 +561,7 @@ void PassManagerBuilder::populateModulePassManager(
   // into separate loop that would otherwise inhibit vectorization.  This is
   // currently only performed for loops marked with the metadata
   // llvm.loop.distribute=true or when -enable-loop-distribute is specified.
-  MPM.add(createLoopDistributePass(/*ProcessAllLoopsByDefault=*/false));
+  MPM.add(createLoopDistributePass());
 
   MPM.add(createLoopVectorizePass(DisableUnrollLoops, LoopVectorize));
 

lib/Transforms/Scalar/LoopDistribute.cpp

@@ -73,11 +73,10 @@ static cl::opt<unsigned> PragmaDistributeSCEVCheckThreshold(
         "The maximum number of SCEV checks allowed for Loop "
         "Distribution for loop marked with #pragma loop distribute(enable)"));
 
-// Note that the initial value for this depends on whether the pass is invoked
-// directly or from the optimization pipeline.
 static cl::opt<bool> EnableLoopDistribute(
     "enable-loop-distribute", cl::Hidden,
-    cl::desc("Enable the new, experimental LoopDistribution Pass"));
+    cl::desc("Enable the new, experimental LoopDistribution Pass"),
+    cl::init(false));
 
 STATISTIC(NumLoopsDistributed, "Number of loops distributed");
 
@@ -875,8 +874,7 @@ private:
 /// Shared implementation between new and old PMs.
 static bool runImpl(Function &F, LoopInfo *LI, DominatorTree *DT,
                     ScalarEvolution *SE, OptimizationRemarkEmitter *ORE,
-                    std::function<const LoopAccessInfo &(Loop &)> &GetLAA,
+                    std::function<const LoopAccessInfo &(Loop &)> &GetLAA) {
-                    bool ProcessAllLoops) {
   // Build up a worklist of inner-loops to vectorize. This is necessary as the
   // act of distributing a loop creates new loops and can invalidate iterators
   // across the loops.
@@ -895,7 +893,7 @@ static bool runImpl(Function &F, LoopInfo *LI, DominatorTree *DT,
 
     // If distribution was forced for the specific loop to be
     // enabled/disabled, follow that.  Otherwise use the global flag.
-    if (LDL.isForced().getValueOr(ProcessAllLoops))
+    if (LDL.isForced().getValueOr(EnableLoopDistribute))
       Changed |= LDL.processLoop(GetLAA);
   }
 
@@ -906,15 +904,8 @@ static bool runImpl(Function &F, LoopInfo *LI, DominatorTree *DT,
 /// \brief The pass class.
 class LoopDistributeLegacy : public FunctionPass {
 public:
-  /// \p ProcessAllLoopsByDefault specifies whether loop distribution should be
+  LoopDistributeLegacy() : FunctionPass(ID) {
-  /// performed by default.  Pass -enable-loop-distribute={0,1} overrides this
-  /// default.  We use this to keep LoopDistribution off by default when invoked
-  /// from the optimization pipeline but on when invoked explicitly from opt.
-  LoopDistributeLegacy(bool ProcessAllLoopsByDefault = true)
-      : FunctionPass(ID), ProcessAllLoops(ProcessAllLoopsByDefault) {
     // The default is set by the caller.
-    if (EnableLoopDistribute.getNumOccurrences() > 0)
-      ProcessAllLoops = EnableLoopDistribute;
     initializeLoopDistributeLegacyPass(*PassRegistry::getPassRegistry());
   }
 
@@ -930,7 +921,7 @@ public:
     std::function<const LoopAccessInfo &(Loop &)> GetLAA =
         [&](Loop &L) -> const LoopAccessInfo & { return LAA->getInfo(&L); };
 
-    return runImpl(F, LI, DT, SE, ORE, GetLAA, ProcessAllLoops);
+    return runImpl(F, LI, DT, SE, ORE, GetLAA);
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {
@@ -945,23 +936,11 @@ public:
   }
 
   static char ID;
-
-private:
-  /// \brief Whether distribution should be on in this function.  The per-loop
-  /// pragma can override this.
-  bool ProcessAllLoops;
 };
 } // anonymous namespace
 
 PreservedAnalyses LoopDistributePass::run(Function &F,
                                           FunctionAnalysisManager &AM) {
-  // FIXME: This does not currently match the behavior from the old PM.
-  // ProcessAllLoops with the old PM defaults to true when invoked from opt and
-  // false when invoked from the optimization pipeline.
-  bool ProcessAllLoops = false;
-  if (EnableLoopDistribute.getNumOccurrences() > 0)
-    ProcessAllLoops = EnableLoopDistribute;
-
   auto &LI = AM.getResult<LoopAnalysis>(F);
   auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
   auto &SE = AM.getResult<ScalarEvolutionAnalysis>(F);
@@ -973,7 +952,7 @@ PreservedAnalyses LoopDistributePass::run(Function &F,
     return LAM.getResult<LoopAccessAnalysis>(L);
   };
 
-  bool Changed = runImpl(F, &LI, &DT, &SE, &ORE, GetLAA, ProcessAllLoops);
+  bool Changed = runImpl(F, &LI, &DT, &SE, &ORE, GetLAA);
   if (!Changed)
     return PreservedAnalyses::all();
   PreservedAnalyses PA;
@@ -996,7 +975,5 @@ INITIALIZE_PASS_DEPENDENCY(OptimizationRemarkEmitterWrapperPass)
 INITIALIZE_PASS_END(LoopDistributeLegacy, LDIST_NAME, ldist_name, false, false)
 
 namespace llvm {
-FunctionPass *createLoopDistributePass(bool ProcessAllLoopsByDefault) {
+FunctionPass *createLoopDistributePass() { return new LoopDistributeLegacy(); }
-  return new LoopDistributeLegacy(ProcessAllLoopsByDefault);
-}
 }

test/Transforms/LoopDistribute/basic-with-memchecks.ll

@@ -1,7 +1,7 @@
-; RUN: opt -basicaa -loop-distribute -verify-loop-info -verify-dom-info -S \
+; RUN: opt -basicaa -loop-distribute -enable-loop-distribute -verify-loop-info -verify-dom-info -S \
 ; RUN:   < %s | FileCheck %s
 
-; RUN: opt -basicaa -loop-distribute -loop-vectorize -force-vector-width=4 \
+; RUN: opt -basicaa -loop-distribute -enable-loop-distribute -loop-vectorize -force-vector-width=4 \
 ; RUN:   -verify-loop-info -verify-dom-info -S < %s | \
 ; RUN:   FileCheck --check-prefix=VECTORIZE %s
 

test/Transforms/LoopDistribute/basic.ll

@@ -1,10 +1,10 @@
-; RUN: opt -basicaa -loop-distribute -verify-loop-info -verify-dom-info -S \
+; RUN: opt -basicaa -loop-distribute -enable-loop-distribute -verify-loop-info -verify-dom-info -S \
 ; RUN:   < %s | FileCheck %s
 
-; RUN: opt -basicaa -loop-distribute -verify-loop-info -verify-dom-info \
+; RUN: opt -basicaa -loop-distribute -enable-loop-distribute -verify-loop-info -verify-dom-info \
 ; RUN:   -loop-accesses -analyze < %s | FileCheck %s --check-prefix=ANALYSIS
 
-; RUN: opt -basicaa -loop-distribute -loop-vectorize -force-vector-width=4 -S \
+; RUN: opt -basicaa -loop-distribute -enable-loop-distribute -loop-vectorize -force-vector-width=4 -S \
 ; RUN:   < %s | FileCheck %s --check-prefix=VECTORIZE
 
 ; We should distribute this loop into a safe (2nd statement) and unsafe loop

test/Transforms/LoopDistribute/bounds-expansion-bug.ll

@@ -1,4 +1,4 @@
-; RUN: opt -basicaa -loop-distribute -S < %s | FileCheck %s
+; RUN: opt -basicaa -loop-distribute -enable-loop-distribute -S < %s | FileCheck %s
 
 ; When emitting the memchecks for:
 ;

test/Transforms/LoopDistribute/crash-in-memcheck-generation.ll

@@ -1,4 +1,4 @@
-; RUN: opt -basicaa -loop-distribute -loop-vectorize -force-vector-width=4 \
+; RUN: opt -basicaa -loop-distribute -enable-loop-distribute -loop-vectorize -force-vector-width=4 \
 ; RUN:   -verify-loop-info -verify-dom-info -S < %s | FileCheck %s
 
 ; If only A and B can alias here, we don't need memchecks to distribute since

test/Transforms/LoopDistribute/diagnostics-with-hotness-lazy-BFI.ll

@@ -1,9 +1,9 @@
 ; Check that BFI is not computed when -pass-remarks-with-hotness is off
 
-; RUN: opt -loop-distribute -S -pass-remarks-missed=loop-distribute \
+; RUN: opt -loop-distribute -enable-loop-distribute -S -pass-remarks-missed=loop-distribute \
 ; RUN:     -debug-only=block-freq,branch-prob -pass-remarks-with-hotness \
 ; RUN:     < %s 2>&1 | FileCheck %s --check-prefix=HOTNESS
-; RUN: opt -loop-distribute -S -pass-remarks-missed=loop-distribute \
+; RUN: opt -loop-distribute -enable-loop-distribute -S -pass-remarks-missed=loop-distribute \
 ; RUN:     -debug-only=block-freq,branch-prob \
 ; RUN:     < %s 2>&1 | FileCheck %s --check-prefix=NO_HOTNESS
 

test/Transforms/LoopDistribute/diagnostics-with-hotness.ll

@@ -1,7 +1,7 @@
-; RUN: opt -loop-simplify -loop-distribute -S -pass-remarks-missed=loop-distribute \
+; RUN: opt -loop-simplify -loop-distribute -enable-loop-distribute -S -pass-remarks-missed=loop-distribute \
 ; RUN:     -pass-remarks-analysis=loop-distribute \
 ; RUN:     -pass-remarks-with-hotness < %s 2>&1 | FileCheck %s --check-prefix=HOTNESS
-; RUN: opt -loop-simplify -loop-distribute -S -pass-remarks-missed=loop-distribute \
+; RUN: opt -loop-simplify -loop-distribute -enable-loop-distribute -S -pass-remarks-missed=loop-distribute \
 ; RUN:     -pass-remarks-analysis=loop-distribute \
 ; RUN:                                < %s 2>&1 | FileCheck %s --check-prefix=NO_HOTNESS
 

test/Transforms/LoopDistribute/diagnostics.ll

@@ -1,12 +1,12 @@
-; RUN: opt -loop-simplify -loop-distribute -S < %s 2>&1 \
+; RUN: opt -loop-simplify -loop-distribute -enable-loop-distribute -S < %s 2>&1 \
 ; RUN:     | FileCheck %s --check-prefix=ALWAYS --check-prefix=NO_REMARKS
-; RUN: opt -loop-simplify -loop-distribute -S \
+; RUN: opt -loop-simplify -loop-distribute -enable-loop-distribute -S \
 ; RUN:     -pass-remarks-missed=loop-distribute < %s 2>&1 \
 ; RUN:     | FileCheck %s --check-prefix=ALWAYS --check-prefix=MISSED_REMARKS
-; RUN: opt -loop-simplify -loop-distribute -S \
+; RUN: opt -loop-simplify -loop-distribute -enable-loop-distribute -S \
 ; RUN:     -pass-remarks-analysis=loop-distribute < %s 2>&1 \
 ; RUN:     | FileCheck %s --check-prefix=ALWAYS --check-prefix=ANALYSIS_REMARKS
-; RUN: opt -loop-simplify -loop-distribute -S \
+; RUN: opt -loop-simplify -loop-distribute -enable-loop-distribute -S \
 ; RUN:     -pass-remarks=loop-distribute < %s 2>&1 \
 ; RUN:     | FileCheck %s --check-prefix=ALWAYS --check-prefix=REMARKS
 

test/Transforms/LoopDistribute/no-if-convert.ll

@@ -1,4 +1,4 @@
-; RUN: opt -basicaa -loop-distribute -verify-loop-info -verify-dom-info -S < %s \
+; RUN: opt -basicaa -loop-distribute -enable-loop-distribute -verify-loop-info -verify-dom-info -S < %s \
 ; RUN:   | FileCheck %s
 
 ; We should distribute this loop along === but not along ---.  The last

test/Transforms/LoopDistribute/outside-use.ll

@@ -1,4 +1,4 @@
-; RUN: opt -loop-distribute -verify-loop-info -verify-dom-info -S < %s \
+; RUN: opt -loop-distribute -enable-loop-distribute -verify-loop-info -verify-dom-info -S < %s \
 ; RUN:   | FileCheck %s
 
 ; Check that definitions used outside the loop are handled correctly: (1) they

test/Transforms/LoopDistribute/pr28443.ll

@@ -1,4 +1,4 @@
-; RUN: opt -basicaa -loop-distribute -verify-loop-info -verify-dom-info -S \
+; RUN: opt -basicaa -loop-distribute -enable-loop-distribute -verify-loop-info -verify-dom-info -S \
 ; RUN:   < %s | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"

test/Transforms/LoopDistribute/program-order.ll

@@ -1,4 +1,4 @@
-; RUN: opt -loop-distribute -S -verify-loop-info -verify-dom-info < %s \
+; RUN: opt -loop-distribute -enable-loop-distribute -S -verify-loop-info -verify-dom-info < %s \
 ; RUN:   | FileCheck %s
 
 ; Distributing this loop to avoid the dependence cycle would require to

test/Transforms/LoopDistribute/symbolic-stride.ll

@@ -1,7 +1,7 @@
-; RUN: opt -basicaa -loop-distribute -S < %s | \
+; RUN: opt -basicaa -loop-distribute -enable-loop-distribute -S < %s | \
 ; RUN:     FileCheck %s --check-prefix=ALL --check-prefix=STRIDE_SPEC
 
-; RUN: opt -basicaa -loop-distribute -S -enable-mem-access-versioning=0 < %s | \
+; RUN: opt -basicaa -loop-distribute -enable-loop-distribute -S -enable-mem-access-versioning=0 < %s | \
 ; RUN:     FileCheck %s --check-prefix=ALL --check-prefix=NO_STRIDE_SPEC
 
 ; If we don't speculate stride for 1 we can't distribute along the line

test/Transforms/LoopDistribute/unknown-bounds-for-memchecks.ll

@@ -1,4 +1,4 @@
-; RUN: opt -basicaa -loop-distribute -S < %s | FileCheck %s
+; RUN: opt -basicaa -loop-distribute -enable-loop-distribute -S < %s | FileCheck %s
 
 ; If we can't find the bounds for one of the arrays in order to generate the
 ; memchecks (e.g., C[i * i] below), loop shold not get distributed.

test/Transforms/LoopVersioning/exit-block-dominates-rt-check-block.ll

@@ -2,8 +2,8 @@
 ; if the exit block of the loop (bb0) dominates the runtime check block
 ; (bb1 will become the runtime check block).
 
-; RUN: opt -loop-distribute -verify-dom-info -S -o - %s > %t
+; RUN: opt -loop-distribute -enable-loop-distribute -verify-dom-info -S -o - %s > %t
-; RUN: opt -loop-simplify -loop-distribute -verify-dom-info -S -o - %s > %t
+; RUN: opt -loop-simplify -loop-distribute -enable-loop-distribute -verify-dom-info -S -o - %s > %t
 ; RUN: FileCheck --check-prefix CHECK-VERSIONING -input-file %t %s
 
 ; RUN: opt -loop-versioning -verify-dom-info -S -o - %s > %t

test/Transforms/LoopVersioning/noalias-version-twice.ll

@@ -1,4 +1,4 @@
-; RUN: opt -basicaa -loop-distribute -loop-simplify -scoped-noalias \
+; RUN: opt -basicaa -loop-distribute -enable-loop-distribute -loop-simplify -scoped-noalias \
 ; RUN:     -loop-versioning -S < %s | FileCheck %s
 
 ; Test the metadata generated when versioning an already versioned loop.  Here