[PATCH] D90402: [LoopFlatten] Run it earlier, just before IndVarSimplify

[Sjoerd Meijer via Phabricator via llvm-commits]

SjoerdMeijer created this revision.
SjoerdMeijer added reviewers: ostannard, dmgreen, sanwou01.
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Herald added a project: LLVM.
SjoerdMeijer requested review of this revision.

This is a prep step for widening induction variables of a nested loop in LoopFlatten if this is posssible, to avoid having to perform certain overflow checks. Since IndVarSimplify may already widen induction variables, we want to run LoopFlatten just before IndVarSimplify. This is a minor reshuffle as both passes were already close after each other.

This is separated out from D88880 <https://reviews.llvm.org/D88880>, which is about making LoopFlatten triggeron 64-bit targets too and is the motivation of this work.

PS. No pipeline pass manager test were changed, because LoopFlatten isn't enabled by default yet.


https://reviews.llvm.org/D90402

Files:
  llvm/lib/Passes/PassBuilder.cpp
  llvm/lib/Transforms/IPO/PassManagerBuilder.cpp


Index: llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
===================================================================
--- llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -441,6 +441,10 @@
   MPM.add(createCFGSimplificationPass());
   MPM.add(createInstructionCombiningPass());
   // We resume loop passes creating a second loop pipeline here.
+  if (EnableLoopFlatten) {
+    MPM.add(createLoopFlattenPass()); // Flatten loops
+    MPM.add(createLoopSimplifyCFGPass());
+  }
   MPM.add(createIndVarSimplifyPass());        // Canonicalize indvars
   MPM.add(createLoopIdiomPass());             // Recognize idioms like memset.
   addExtensionsToPM(EP_LateLoopOptimizations, MPM);
@@ -448,10 +452,6 @@
 
   if (EnableLoopInterchange)
     MPM.add(createLoopInterchangePass()); // Interchange loops
-  if (EnableLoopFlatten) {
-    MPM.add(createLoopFlattenPass()); // Flatten loops
-    MPM.add(createLoopSimplifyCFGPass());
-  }
 
   // Unroll small loops
   MPM.add(createSimpleLoopUnrollPass(OptLevel, DisableUnrollLoops,
@@ -1045,12 +1045,12 @@
   PM.add(createMergedLoadStoreMotionPass()); // Merge ld/st in diamonds.
 
   // More loops are countable; try to optimize them.
+  if (EnableLoopFlatten)
+    PM.add(createLoopFlattenPass());
   PM.add(createIndVarSimplifyPass());
   PM.add(createLoopDeletionPass());
   if (EnableLoopInterchange)
     PM.add(createLoopInterchangePass());
-  if (EnableLoopFlatten)
-    PM.add(createLoopFlattenPass());
 
   // Unroll small loops
   PM.add(createSimpleLoopUnrollPass(OptLevel, DisableUnrollLoops,
Index: llvm/lib/Passes/PassBuilder.cpp
===================================================================
--- llvm/lib/Passes/PassBuilder.cpp
+++ llvm/lib/Passes/PassBuilder.cpp
@@ -522,6 +522,10 @@
   // TODO: Investigate promotion cap for O1.
   LPM1.addPass(LICMPass(PTO.LicmMssaOptCap, PTO.LicmMssaNoAccForPromotionCap));
   LPM1.addPass(SimpleLoopUnswitchPass());
+
+  if (EnableLoopFlatten)
+    LPM2.addPass(LoopFlattenPass());
+
   LPM2.addPass(IndVarSimplifyPass());
   LPM2.addPass(LoopIdiomRecognizePass());
 
@@ -529,8 +533,6 @@
     C(LPM2, Level);
 
   LPM2.addPass(LoopDeletionPass());
-  if (EnableLoopFlatten)
-    LPM2.addPass(LoopFlattenPass());
   // Do not enable unrolling in PreLinkThinLTO phase during sample PGO
   // because it changes IR to makes profile annotation in back compile
   // inaccurate. The normal unroller doesn't pay attention to forced full unroll


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