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

[MengXuan Cai via Phabricator via llvm-commits]

Narutoworld created this revision.
Narutoworld added reviewers: bjope, aeubanks.
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Narutoworld requested review of this revision.

This patch tries to fix this issue <https://github.com/llvm/llvm-project/issues/50379>.

Loop Fusion (Function Pass) requires loops in simplified form. With legacy-pm, **loop-simplify** pass is added as a dependency for **loop-fusion**. But the new pass manager does not always ensure this format. This patch tries to invoke simplifyLoop() on loops that are not in simplified form.


Repository:
  rG LLVM Github Monorepo

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 +1,19 @@
+; RUN: opt -enable-new-pm=1 -loop-fusion  < %s
+
+define dso_local void @v_5_0() {
+entry:
+  br label %for.body
+
+for.cond.cleanup:                                 ; preds = %for.body
+  br i1 undef, label %for.body6, label %for.cond.cleanup5
+
+for.body:                                         ; preds = %for.body, %entry
+  br i1 undef, 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* undef, 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;
 
@@ -593,6 +594,13 @@
           });
         }
 #endif
+        for (Loop *L : LV) {
+          if (!L->isLoopSimplifyForm())
+            Changed |= simplifyLoop(L, &DT, &LT, &SE, &AC, nullptr,
+                                    /*PreserveLCSSA=*/false);
+        }
+        if (Changed)
+          PDT.recalculate(F);
 
         collectFusionCandidates(LV);
         Changed |= fuseCandidates();


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