[PATCH] D68535: Fix loop unrolling initialization in the new pass manager

[Eric Christopher via Phabricator via llvm-commits]

echristo created this revision.
echristo added reviewers: chandlerc, hfinkel.
Herald added subscribers: llvm-commits, cfe-commits, hiraditya, mcrosier.
Herald added projects: clang, LLVM.

In the new pass manager use PTO.LoopUnrolling to determine when and how
we will unroll loops. Also comment a few occasions where we need to
know whether or not we're forcing the unwinder or not.

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.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D68535

Files:
  clang/test/Misc/loop-opt-setup.c
  llvm/lib/Passes/PassBuilder.cpp


Index: llvm/lib/Passes/PassBuilder.cpp
===================================================================
--- llvm/lib/Passes/PassBuilder.cpp
+++ llvm/lib/Passes/PassBuilder.cpp
@@ -470,8 +470,8 @@
   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);
@@ -950,13 +950,13 @@
   // 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>());
Index: clang/test/Misc/loop-opt-setup.c
===================================================================
--- /dev/null
+++ clang/test/Misc/loop-opt-setup.c
@@ -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
+


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