[PATCH] D136781: ensure loop-simplifed form when running loop-fusion pass with new-PM

[MengXuan Cai via Phabricator via llvm-commits]

Narutoworld updated this revision to Diff 471390.
Narutoworld marked an inline comment as done.
Narutoworld added a comment.

Recalculating post dominator tree for the whole function if any loops are transformed by `simplifyLoop()`.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D136781/new/

https://reviews.llvm.org/D136781

Files:
  llvm/lib/Transforms/Scalar/LoopFuse.cpp
  llvm/test/Transforms/LoopFusion/ensure_loop_simplify_form.ll


Index: llvm/test/Transforms/LoopFusion/ensure_loop_simplify_form.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LoopFusion/ensure_loop_simplify_form.ll
@@ -0,0 +1,35 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes=loop-fusion -S | FileCheck %s
+
+define void @v_5_0(i32* %dummy) {
+; CHECK-LABEL: @v_5_0(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    br i1 true, label [[FOR_BODY6_PREHEADER:%.*]], label [[FOR_COND_CLEANUP5:%.*]]
+; CHECK:       for.body6.preheader:
+; CHECK-NEXT:    br label [[FOR_BODY6:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    br i1 false, label [[FOR_COND_CLEANUP:%.*]], label [[FOR_BODY]]
+; CHECK:       for.cond.cleanup5:
+; CHECK-NEXT:    ret void
+; CHECK:       for.body6:
+; CHECK-NEXT:    [[V_LOOP_2_0_V_LOOP_2_0_V_LOOP_2_0_18:%.*]] = load volatile i32, i32* [[DUMMY:%.*]], align 1
+; CHECK-NEXT:    br label [[FOR_BODY6]]
+;
+entry:
+  br label %for.body
+
+for.cond.cleanup:                                 ; preds = %for.body
+  br i1 true, label %for.body6, label %for.cond.cleanup5
+
+for.body:                                         ; preds = %for.body, %entry
+  br i1 false, label %for.cond.cleanup, label %for.body
+
+for.cond.cleanup5:                                ; preds = %for.cond.cleanup
+  ret void
+
+for.body6:                                        ; preds = %for.body6, %for.cond.cleanup
+  %v_loop_2.0.v_loop_2.0.v_loop_2.0.18 = load volatile i32, i32* %dummy, align 1
+  br label %for.body6
+}
Index: llvm/lib/Transforms/Scalar/LoopFuse.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopFuse.cpp
+++ llvm/lib/Transforms/Scalar/LoopFuse.cpp
@@ -67,6 +67,7 @@
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/CodeMoverUtils.h"
 #include "llvm/Transforms/Utils/LoopPeel.h"
+#include "llvm/Transforms/Utils/LoopSimplify.h"
 
 using namespace llvm;
 
@@ -2085,8 +2086,20 @@
   const TargetTransformInfo &TTI = AM.getResult<TargetIRAnalysis>(F);
   const DataLayout &DL = F.getParent()->getDataLayout();
 
+  // Ensure loops are in simplifed form which is a pre-requisite for loop fusion
+  // pass. Added only for new PM since the legacy PM has already added
+  // LoopSimplify pass as a dependency.
+  bool Changed = false;
+  for (auto &L : LI) {
+    if (!L->isLoopSimplifyForm())
+      Changed |= simplifyLoop(L, &DT, &LI, &SE, &AC, nullptr,
+                              false /* PreserveLCSSA */);
+  }
+  if (Changed)
+    PDT.recalculate(F);
+
   LoopFuser LF(LI, DT, DI, SE, PDT, ORE, DL, AC, TTI);
-  bool Changed = LF.fuseLoops(F);
+  Changed |= LF.fuseLoops(F);
   if (!Changed)
     return PreservedAnalyses::all();
 


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