[flang] Runs FIR SimplifyRegionLitePass pass after calling the inliner

In flang pipeline, the inliner calls createCanonicalizerPass with the region
simplification disabled. The inliner pass does canonicalization even if
no inlining happens. After canonicalization, FIR lite region simplification
must be called to get rid of unreachable regions.
This code exposes the need to run SimplifyRegionLitePass after the inliner is
called with FIR pipeline.

Differential Revision: https://reviews.llvm.org/D130484

5 files changed, 40 insertions, 0 deletions

diff --git a/flang/include/flang/Tools/CLOptions.inc b/flang/include/flang/Tools/CLOptions.inc
index 6d5ed9cbee87..5cf89d79ffc8 100644
--- a/flang/include/flang/Tools/CLOptions.inc
+++ b/flang/include/flang/Tools/CLOptions.inc
@@ -176,6 +176,7 @@ inline void createDefaultFIROptimizerPassPipeline(
   llvm::StringMap<mlir::OpPassManager> pipelines;
   pm.addPass(
       mlir::createInlinerPass(pipelines, defaultFlangInlinerOptPipeline));
+  pm.addPass(fir::createSimplifyRegionLitePass());
   pm.addPass(mlir::createCSEPass());
 
   // convert control flow to CFG form
diff --git a/flang/test/Driver/bbc-mlir-pass-pipeline.f90 b/flang/test/Driver/bbc-mlir-pass-pipeline.f90
index 45ff3ebfbc22..388cc0574145 100644
--- a/flang/test/Driver/bbc-mlir-pass-pipeline.f90
+++ b/flang/test/Driver/bbc-mlir-pass-pipeline.f90
@@ -32,6 +32,7 @@ end program
 ! CHECK-NEXT:   MemoryAllocationOpt
 
 ! CHECK-NEXT: Inliner
+! CHECK-NEXT: SimplifyRegionLite
 ! CHECK-NEXT: CSE
 ! CHECK-NEXT:   (S) 0 num-cse'd - Number of operations CSE'd
 ! CHECK-NEXT:   (S) 0 num-dce'd - Number of operations DCE'd
diff --git a/flang/test/Driver/mlir-pass-pipeline.f90 b/flang/test/Driver/mlir-pass-pipeline.f90
index 78104285db57..5d9f0ce32b79 100644
--- a/flang/test/Driver/mlir-pass-pipeline.f90
+++ b/flang/test/Driver/mlir-pass-pipeline.f90
@@ -35,6 +35,7 @@ end program
 ! ALL-NEXT:   MemoryAllocationOpt
 
 ! ALL-NEXT: Inliner
+! ALL-NEXT: SimplifyRegionLite
 ! ALL-NEXT: CSE
 ! ALL-NEXT:   (S) 0 num-cse'd - Number of operations CSE'd
 ! ALL-NEXT:   (S) 0 num-dce'd - Number of operations DCE'd
diff --git a/flang/test/Fir/basic-program.fir b/flang/test/Fir/basic-program.fir
index 8d1aab12c9a0..29efa845fafa 100644
--- a/flang/test/Fir/basic-program.fir
+++ b/flang/test/Fir/basic-program.fir
@@ -35,6 +35,7 @@ func.func @_QQmain() {
 // PASSES-NEXT:   MemoryAllocationOpt
 
 // PASSES-NEXT: Inliner
+// PASSES-NEXT: SimplifyRegionLite
 // PASSES-NEXT: CSE
 // PASSES-NEXT:   (S) 0 num-cse'd - Number of operations CSE'd
 // PASSES-NEXT:   (S) 0 num-dce'd - Number of operations DCE'd
diff --git a/flang/test/Fir/simplify-region-lite-after-inliner.fir b/flang/test/Fir/simplify-region-lite-after-inliner.fir
new file mode 100644
index 000000000000..c09612b5dabe
--- /dev/null
+++ b/flang/test/Fir/simplify-region-lite-after-inliner.fir
@@ -0,0 +1,36 @@
+// RUN: tco %s | FileCheck %s
+
+
+// In flang pipeline, the inliner calls createCanonicalizerPass with the region
+// simplification disabled. The inliner pass does canonicalization even if
+// no inlining happens. After canonicalization, FIR lite region simplification
+// must be called to get rid of unreachable regions.
+// This code exposes the need to run SimplifyRegionLitePass after the inliner is
+// called with FIR pipeline.
+
+
+func.func @repro(%arg0: i8, %arg1: i8) {
+  %c34_i8 = arith.constant 34 : i8
+  %c-1_i8 = arith.constant -1 : i8
+  %2 = arith.xori %c34_i8, %c-1_i8 : i8
+  %3 = arith.andi %arg0, %c34_i8 : i8
+  %4 = arith.andi %arg1, %2 : i8
+  %5 = arith.ori %3, %4 : i8
+  %c34_i8_0 = arith.constant 34 : i8
+  %7 = arith.andi %arg0, %c34_i8_0 : i8
+  %c-35_i8 = arith.constant -35 : i8
+  %9 = arith.andi %arg1, %c-35_i8 : i8
+  %10 = arith.ori %7, %9 : i8
+  %11 = arith.cmpi ne, %5, %10 : i8
+  cf.cond_br %11, ^bb1, ^bb2
+^bb1:  // pred: ^bb0
+  %13 = func.call @foo() : () -> none
+  cf.br ^bb2
+^bb2:  // pred: ^bb0, ^bb2
+  return
+}
+func.func private @foo() -> none
+
+
+// CHECK: define void @repro(i8 %0, i8 %1)
+//   CHECK-NEXT  ret void