[mlir:DataFlowAnalysis] Reprocess the arguments of already executable edges

This fixes a bug where we discover new information about the arguments of an
already executable edge, but don't visit the arguments. We only visit the arguments, and not the block itself, so this commit shouldn't really affect performance at all.

Fixes PR#51871

Differential Revision: https://reviews.llvm.org/D110197

diff --git a/mlir/lib/Analysis/DataFlowAnalysis.cpp b/mlir/lib/Analysis/DataFlowAnalysis.cpp
index b5a5e17..b91d2de 100644 (file)
--- a/mlir/lib/Analysis/DataFlowAnalysis.cpp
+++ b/mlir/lib/Analysis/DataFlowAnalysis.cpp
@@ -722,8 +722,7 @@ bool ForwardDataFlowSolver::isBlockExecutable(Block *block) const {
 }
 
 void ForwardDataFlowSolver::markEdgeExecutable(Block *from, Block *to) {
-  if (!executableEdges.insert(std::make_pair(from, to)).second)
-    return;
+  executableEdges.insert(std::make_pair(from, to));
 
   // Mark the destination as executable, and reprocess its arguments if it was
   // already executable.

diff --git a/mlir/test/Transforms/sccp.mlir b/mlir/test/Transforms/sccp.mlir
index 39d9acd..29499f3 100644 (file)
--- a/mlir/test/Transforms/sccp.mlir
+++ b/mlir/test/Transforms/sccp.mlir
@@ -178,3 +178,23 @@ func @simple_loop_overdefined(%arg0 : i32, %cond1 : i1) -> i32 {
 
   return %arg : i32
 }
+
+// Check that we reprocess executable edges when information changes.
+
+// CHECK-LABEL: func @recheck_executable_edge
+func @recheck_executable_edge(%cond0: i1) -> (i1, i1) {
+  %true = constant true
+  %false = constant false
+  cond_br %cond0, ^bb_1a, ^bb2(%false : i1)
+^bb_1a:
+  br ^bb2(%true : i1)
+
+^bb2(%x: i1):
+  // CHECK: ^bb2(%[[X:.*]]: i1):
+  br ^bb3(%x : i1)
+
+^bb3(%y: i1):
+  // CHECK: ^bb3(%[[Y:.*]]: i1):
+  // CHECK: return %[[X]], %[[Y]]
+  return %x, %y : i1, i1
+}