[llvm] 2ef4791 - [LoopFlatten] Run it earlier, just before IndVarSimplify

[Sjoerd Meijer via llvm-commits]

Author: Sjoerd Meijer
Date: 2020-11-10T20:22:41Z
New Revision: 2ef47910d5a14307e48419b02a67c453c179032f

URL: https://github.com/llvm/llvm-project/commit/2ef47910d5a14307e48419b02a67c453c179032f
DIFF: https://github.com/llvm/llvm-project/commit/2ef47910d5a14307e48419b02a67c453c179032f.diff

LOG: [LoopFlatten] Run it earlier, just before IndVarSimplify

This is a prep step for widening induction variables in LoopFlatten if this is
posssible (D90640), 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.

Differential Revision: https://reviews.llvm.org/D90402

Added: 
    

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

Removed: 
    


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diff  --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
index ffaec542b981..a42c8d32379e 100644
--- a/llvm/lib/Passes/PassBuilder.cpp
+++ b/llvm/lib/Passes/PassBuilder.cpp
@@ -535,6 +535,9 @@ PassBuilder::buildO1FunctionSimplificationPipeline(OptimizationLevel Level,
   // TODO: Investigate promotion cap for O1.
   LPM1.addPass(LICMPass(PTO.LicmMssaOptCap, PTO.LicmMssaNoAccForPromotionCap));
   LPM1.addPass(SimpleLoopUnswitchPass());
+
+  if (EnableLoopFlatten)
+    FPM.addPass(LoopFlattenPass());
   LPM2.addPass(IndVarSimplifyPass());
   LPM2.addPass(LoopIdiomRecognizePass());
 
@@ -542,8 +545,6 @@ PassBuilder::buildO1FunctionSimplificationPipeline(OptimizationLevel Level,
     C(LPM2, Level);
 
   LPM2.addPass(LoopDeletionPass());
-  if (EnableLoopFlatten)
-    FPM.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

diff  --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
index b38d51a8d94b..826ca7be88e5 100644
--- a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -441,6 +441,10 @@ void PassManagerBuilder::addFunctionSimplificationPasses(
   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 @@ void PassManagerBuilder::addFunctionSimplificationPasses(
 
   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 @@ void PassManagerBuilder::addLTOOptimizationPasses(legacy::PassManagerBase &PM) {
   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,