[PATCH] D78012: [MLIR] Fix dominance info method - properlyDominates

[Uday Bondhugula via Phabricator via llvm-commits]

bondhugula updated this revision to Diff 256955.
bondhugula added a comment.

Update comments.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D78012/new/

https://reviews.llvm.org/D78012

Files:
  mlir/lib/Analysis/Dominance.cpp
  mlir/test/IR/dominance.mlir


Index: mlir/test/IR/dominance.mlir
===================================================================
--- /dev/null
+++ mlir/test/IR/dominance.mlir
@@ -0,0 +1,38 @@
+// RUN: mlir-opt %s | FileCheck %s
+
+// Verify dominance related functions in "cyclic" cases.
+// CHECK-LABEL: func @dominance
+func @dominance(%n: i32, %p : i1) -> i32 {
+  %x = addi %n, %n : i32
+  return %x : i32
+
+  // Self loop.
+^bar:
+  %y = addi %z, %x : i32
+  // muli does dominate addi.
+  %z = muli %y, %y : i32
+  br ^bar
+
+  // abc and xyz cycle.
+^abc:
+  %a = addi %b, %x : i32
+  // muli does dominate addi.
+  %b = muli %a, %a : i32
+  br ^xyz
+
+^xyz:
+  br ^abc
+
+  // c1, c2, c3 are an SCC.
+^c1:
+  %u = addi %v, %x : i32
+  // muli does dominate addi.
+  %v = muli %u, %u : i32
+  cond_br %p, ^c2, ^c3
+
+^c2:
+  br ^c1
+
+^c3:
+  br ^c1
+}
Index: mlir/lib/Analysis/Dominance.cpp
===================================================================
--- mlir/lib/Analysis/Dominance.cpp
+++ mlir/lib/Analysis/Dominance.cpp
@@ -183,17 +183,29 @@
 // DominanceInfo
 //===----------------------------------------------------------------------===//
 
-/// Return true if operation A properly dominates operation B.
+/// Returns true if operation A properly dominates operation B.
 bool DominanceInfo::properlyDominates(Operation *a, Operation *b) {
   auto *aBlock = a->getBlock(), *bBlock = b->getBlock();
 
-  // If a or b are not within a block, then a does not dominate b.
+  // If a or b are not within a block, then a does not properly dominate b.
   if (!aBlock || !bBlock)
     return false;
 
   // If the blocks are the same, then check if b is before a in the block.
-  if (aBlock == bBlock)
-    return a->isBeforeInBlock(b);
+  if (aBlock == bBlock) {
+    if (a->isBeforeInBlock(b))
+      return true;
+
+    // Even if b is before a in their block, if aBlock dominates all
+    // predecessors of aBlock, a dominates b.
+
+    // Can't be equal for proper dominance.
+    if (a == b || aBlock->hasNoPredecessors())
+      return false;
+
+    return llvm::all_of(aBlock->getPredecessors(),
+                        [&](Block *p) { return dominates(aBlock, p); });
+  }
 
   // Traverse up b's hierarchy to check if b's block is contained in a's.
   if (auto *bAncestor = aBlock->findAncestorOpInBlock(*b)) {


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