[PATCH] D71687: Fix full loop unrolling initialization in new pass manager

[Eric Christopher via Phabricator via llvm-commits]

echristo updated this revision to Diff 250232.
echristo added a comment.

Fix comments around full unroller.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71687/new/

https://reviews.llvm.org/D71687

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
@@ -496,12 +496,13 @@
   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)
Index: clang/test/Misc/loop-opt-setup.c
===================================================================
--- clang/test/Misc/loop-opt-setup.c
+++ clang/test/Misc/loop-opt-setup.c
@@ -1,5 +1,5 @@
-// RUN: %clang -O1 -fexperimental-new-pass-manager -fno-unroll-loops -S -o - %s -emit-llvm | FileCheck %s
-// RUN: %clang -O1 -fno-experimental-new-pass-manager -fno-unroll-loops -S -o - %s -emit-llvm | FileCheck %s
+// RUN: %clang -O1 -fexperimental-new-pass-manager -fno-unroll-loops -S -o - %s -emit-llvm | FileCheck %s -check-prefix=CHECK-NEWPM
+// RUN: %clang -O1 -fno-experimental-new-pass-manager -fno-unroll-loops -S -o - %s -emit-llvm | FileCheck %s -check-prefix=CHECK-OLDPM
 extern int a[16];
 int b = 0;
 int foo(void) {
@@ -8,5 +8,34 @@
     a[i] = b += 2;
   return b;
 }
+// Check br i1 to make sure that the loop is fully unrolled
 // CHECK-NOT: br i1
 
+inline void Helper() {
+  const int* nodes[5];
+  int num_active = 5;
+
+  while (num_active) {
+#pragma clang loop unroll(full)
+    for (int i = 0; i < 5; ++i) {
+      if (nodes[i]) {
+        --num_active;
+      }
+    }
+  }
+}
+
+void Run() {
+  Helper();
+}
+
+// Check br i1 to make sure the loop is gone, there will still be a label branch for the infinite loop.
+// CHECK-NEWPM-NOT: br i1
+
+// The old pass manager doesn't remove the loop so check for 5 load i32*.
+// CHECK-OLDPM: Helper
+// CHECK-OLDPM: load i32*
+// CHECK-OLDPM: load i32*
+// CHECK-OLDPM: load i32*
+// CHECK-OLDPM: load i32*
+// CHECK-OLDPM: load i32*


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