[CIR][Transforms] Simplify redundant bitcasts

Author: seven-mile

clang/lib/CIR/Dialect/Transforms/MergeCleanups.cpp

@@ -34,7 +34,7 @@ namespace {
 /// To:
 ///   ^bb0:
 ///     cir.return
-struct RemoveRedudantBranches : public OpRewritePattern<BrOp> {
+struct RemoveRedundantBranches : public OpRewritePattern<BrOp> {
   using OpRewritePattern<BrOp>::OpRewritePattern;
 
   LogicalResult matchAndRewrite(BrOp op,
@@ -80,6 +80,22 @@ struct RemoveEmptySwitch : public OpRewritePattern<SwitchOp> {
   }
 };
 
+struct RemoveRedundantBitcast : OpRewritePattern<CastOp> {
+  using OpRewritePattern<CastOp>::OpRewritePattern;
+
+  LogicalResult matchAndRewrite(CastOp op,
+                                PatternRewriter &rewriter) const final {
+    if (op.getKind() != mlir::cir::CastKind::bitcast) {
+      return failure();
+    }
+    if (op.getSrc().getType() != op.getResult().getType()) {
+      return failure();
+    }
+    rewriter.replaceOp(op, op.getSrc());
+    return success();
+  }
+};
+
 //===----------------------------------------------------------------------===//
 // MergeCleanupsPass
 //===----------------------------------------------------------------------===//
@@ -101,9 +117,10 @@ struct MergeCleanupsPass : public MergeCleanupsBase<MergeCleanupsPass> {
 void populateMergeCleanupPatterns(RewritePatternSet &patterns) {
   // clang-format off
   patterns.add<
-    RemoveRedudantBranches,
+    RemoveRedundantBranches,
     RemoveEmptyScope,
-    RemoveEmptySwitch
+    RemoveEmptySwitch,
+    RemoveRedundantBitcast
   >(patterns.getContext());
   // clang-format on
 }
@@ -116,7 +133,7 @@ void MergeCleanupsPass::runOnOperation() {
   // Collect operations to apply patterns.
   SmallVector<Operation *, 16> ops;
   getOperation()->walk([&](Operation *op) {
-    if (isa<BrOp, BrCondOp, ScopeOp, SwitchOp>(op))
+    if (isa<BrOp, BrCondOp, ScopeOp, SwitchOp, CastOp>(op))
       ops.push_back(op);
   });
 

clang/test/CIR/CodeGen/no-prototype.c

@@ -36,8 +36,7 @@ int noProto2();
 int test2(int x) {
   return noProto2(x);
   // CHECK:  [[GGO:%.*]] = cir.get_global @noProto2 : !cir.ptr<!cir.func<!s32i (!s32i)>>
-  // CHECK:  [[CAST:%.*]] = cir.cast(bitcast, %3 : !cir.ptr<!cir.func<!s32i (!s32i)>>), !cir.ptr<!cir.func<!s32i (!s32i)>>
-  // CHECK:  {{.*}} = cir.call [[CAST]](%{{[0-9]+}}) : (!cir.ptr<!cir.func<!s32i (!s32i)>>, !s32i) -> !s32i
+  // CHECK:  {{.*}} = cir.call [[GGO]](%{{[0-9]+}}) : (!cir.ptr<!cir.func<!s32i (!s32i)>>, !s32i) -> !s32i
 }
 int noProto2(int x) { return x; }
 // CHECK: cir.func no_proto @noProto2(%arg0: !s32i {{.+}}) -> !s32i