[LoopUnrollAndJam] Allow unroll and jam loops forced by user.

Summary: Allow unroll and jam loops forced by user.
LoopUnrollAndJamPass is still disabled by default in the NPM pipeline,
and can be controlled by -enable-npm-unroll-and-jam.

Reviewed By: Meinersbur, dmgreen

Differential Revision: https://reviews.llvm.org/D87786

Author: Whitney Tsang

llvm/lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp

@@ -288,6 +288,13 @@ tryToUnrollAndJamLoop(Loop *L, DominatorTree &DT, LoopInfo *LI,
                                  None, None, None, None, None);
   TargetTransformInfo::PeelingPreferences PP =
       gatherPeelingPreferences(L, SE, TTI, None, None);
+
+  TransformationMode EnableMode = hasUnrollAndJamTransformation(L);
+  if (EnableMode & TM_Disable)
+    return LoopUnrollResult::Unmodified;
+  if (EnableMode & TM_ForcedByUser)
+    UP.UnrollAndJam = true;
+
   if (AllowUnrollAndJam.getNumOccurrences() > 0)
     UP.UnrollAndJam = AllowUnrollAndJam;
   if (UnrollAndJamThreshold.getNumOccurrences() > 0)
@@ -300,10 +307,6 @@ tryToUnrollAndJamLoop(Loop *L, DominatorTree &DT, LoopInfo *LI,
                     << L->getHeader()->getParent()->getName() << "] Loop %"
                     << L->getHeader()->getName() << "\n");
 
-  TransformationMode EnableMode = hasUnrollAndJamTransformation(L);
-  if (EnableMode & TM_Disable)
-    return LoopUnrollResult::Unmodified;
-
   // A loop with any unroll pragma (enabling/disabling/count/etc) is left for
   // the unroller, so long as it does not explicitly have unroll_and_jam
   // metadata. This means #pragma nounroll will disable unroll and jam as well

llvm/test/Transforms/LoopUnrollAndJam/pragma-explicit.ll

@@ -1,5 +1,5 @@
-; RUN: opt -loop-unroll-and-jam -allow-unroll-and-jam -unroll-runtime -unroll-partial-threshold=60 < %s -S | FileCheck %s
-; RUN: opt -aa-pipeline=tbaa,basic-aa -passes='loop-unroll-and-jam' -allow-unroll-and-jam -unroll-runtime -unroll-partial-threshold=60 < %s -S | FileCheck %s
+; RUN: opt -loop-unroll-and-jam -unroll-runtime -unroll-partial-threshold=60 < %s -S | FileCheck %s
+; RUN: opt -aa-pipeline=tbaa,basic-aa -passes='loop-unroll-and-jam' -unroll-runtime -unroll-partial-threshold=60 < %s -S | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"