Merge commit 'd04de7b4cb79' from llvm.org/release/21.x into stable/21.x

Author: git apple-llvm automerger

mlir/lib/Transforms/Utils/GreedyPatternRewriteDriver.cpp

@@ -871,7 +871,18 @@ LogicalResult RegionPatternRewriteDriver::simplify(bool *changed) && {
 
     ctx->executeAction<GreedyPatternRewriteIteration>(
         [&] {
-          continueRewrites = processWorklist();
+          continueRewrites = false;
+
+          // Erase unreachable blocks
+          // Operations like:
+          //   %add = arith.addi %add, %add : i64
+          // are legal in unreachable code. Unfortunately many patterns would be
+          // unsafe to apply on such IR and can lead to crashes or infinite
+          // loops.
+          continueRewrites |=
+              succeeded(eraseUnreachableBlocks(rewriter, region));
+
+          continueRewrites |= processWorklist();
 
           // After applying patterns, make sure that the CFG of each of the
           // regions is kept up to date.

mlir/test/Dialect/Arith/canonicalize.mlir

@@ -3363,3 +3363,18 @@ func.func @bf16_fma(%arg0: vector<32x32x32xbf16>, %arg1: vector<32x32x32xbf16>,
     }
   }
 #-}
+
+// CHECK-LABEL: func @unreachable()
+// CHECK-NEXT: return
+// CHECK-NOT: arith
+func.func @unreachable() {
+  return
+^unreachable:
+  %c1_i64 = arith.constant 1 : i64
+  // This self referencing operation is legal in an unreachable block.
+  // Many patterns are unsafe with respect to this kind of situation,
+  // check that we don't infinite loop here.
+  %add = arith.addi %add, %c1_i64 : i64
+  cf.br ^unreachable
+}
+

mlir/test/Transforms/test-canonicalize.mlir

@@ -1,4 +1,4 @@
-// RUN: mlir-opt %s -pass-pipeline='builtin.module(func.func(canonicalize))' | FileCheck %s
+// RUN: mlir-opt %s -pass-pipeline='builtin.module(func.func(canonicalize))' | FileCheck %s  --check-prefixes=CHECK,RS
 // RUN: mlir-opt %s -pass-pipeline='builtin.module(func.func(canonicalize{region-simplify=disabled}))' | FileCheck %s --check-prefixes=CHECK,NO-RS
 
 // CHECK-LABEL: func @remove_op_with_inner_ops_pattern
@@ -80,12 +80,10 @@ func.func @test_dialect_canonicalizer() -> (i32) {
 
 // Check that the option to control region simplification actually works
 // CHECK-LABEL: test_region_simplify
-func.func @test_region_simplify() {
-  // CHECK-NEXT:   return
-  // NO-RS-NEXT: ^bb1
-  // NO-RS-NEXT:   return
-  // CHECK-NEXT: }
-  return
-^bb1:
-  return
+func.func @test_region_simplify(%input1 : i32, %cond : i1) -> i32 {
+  // RS-NEXT: "test.br"(%arg0)[^bb1] : (i32) -> ()
+  // NO-RS-NEXT: "test.br"(%arg0, %arg0)[^bb1] : (i32, i32) -> ()
+   "test.br"(%input1, %input1)[^bb1] : (i32, i32) -> ()
+^bb1(%used_arg : i32, %unused_arg : i32):
+  return %used_arg : i32
 }