[CIR][CIRGen] Create a new block after break and continue

Without this patch, CIR CodeGen continue to generate in the same block
after cir.break and cir.continue, which would cause verification error
because cir.break and cir.continue should appear at the end of blocks.

This patch creates a new dangling block after generating cir.break and
cir.continue to fix the issue.

Author: piggynl

clang/lib/CIR/CodeGen/CIRGenStmt.cpp

@@ -551,20 +551,11 @@ mlir::LogicalResult CIRGenFunction::buildGotoStmt(const GotoStmt &S) {
   // info support just yet, look at this again once we have it.
   assert(builder.getInsertionBlock() && "not yet implemented");
 
-  mlir::Block *currBlock = builder.getBlock();
-  mlir::Block *gotoBlock = currBlock;
-  if (!currBlock->empty() &&
-      currBlock->back().hasTrait<mlir::OpTrait::IsTerminator>()) {
-    gotoBlock = builder.createBlock(builder.getBlock()->getParent());
-    builder.setInsertionPointToEnd(gotoBlock);
-  }
-
-  // A goto marks the end of a block, create a new one for codegen after
-  // buildGotoStmt can resume building in that block.
-
   builder.create<mlir::cir::GotoOp>(getLoc(S.getSourceRange()),
                                     S.getLabel()->getName());
 
+  // A goto marks the end of a block, create a new one for codegen after
+  // buildGotoStmt can resume building in that block.
   // Insert the new block to continue codegen after goto.
   builder.createBlock(builder.getBlock()->getParent());
 
@@ -597,11 +588,19 @@ mlir::LogicalResult CIRGenFunction::buildLabel(const LabelDecl *D) {
 mlir::LogicalResult
 CIRGenFunction::buildContinueStmt(const clang::ContinueStmt &S) {
   builder.createContinue(getLoc(S.getContinueLoc()));
+
+  // Insert the new block to continue codegen after the continue statement.
+  builder.createBlock(builder.getBlock()->getParent());
+
   return mlir::success();
 }
 
 mlir::LogicalResult CIRGenFunction::buildBreakStmt(const clang::BreakStmt &S) {
   builder.createBreak(getLoc(S.getBreakLoc()));
+
+  // Insert the new block to continue codegen after the break statement.
+  builder.createBlock(builder.getBlock()->getParent());
+
   return mlir::success();
 }
 

clang/test/CIR/CodeGen/goto.cpp

@@ -101,26 +101,6 @@ int shouldGenBranch(int x) {
 // NOFLAT:  ^bb1:  
 // NOFLAT:    cir.label "err"
 
-int shouldCreateBlkForGoto(int a) {
-  switch (a) {
-    case(42):
-      break;
-      goto exit;
-    default:
-      return 0;
-  };
-
-exit:
-  return -1;
-
-}
-// NOFLAT: cir.func @_Z22shouldCreateBlkForGotoi
-// NOFLAT:   case (equal, 42) {
-// NOFLAT:     cir.break
-// NOFLAT:   ^bb1:  // no predecessors
-// NOFLAT:     cir.goto "exit"
-// NOFLAT:   }
-
 void severalLabelsInARow(int a) {
   int b = a;
   goto end1;

clang/test/CIR/CodeGen/loop.cpp

@@ -205,3 +205,55 @@ void l6() {
 // CHECK-NEXT:   }
 // CHECK-NEXT:   cir.return
 // CHECK-NEXT: }
+
+void unreachable_after_break() {
+  for (;;) {
+    break;
+    int x = 1;
+  }
+}
+
+// CHECK-NEXT: cir.func @_Z23unreachable_after_breakv()
+// CHECK-NEXT:   cir.scope {
+// CHECK-NEXT:     %0 = cir.alloca !s32i, !cir.ptr<!s32i>, ["x", init] {alignment = 4 : i64}
+// CHECK-NEXT:     cir.for : cond {
+// CHECK-NEXT:       %1 = cir.const #true
+// CHECK-NEXT:       cir.condition(%1)
+// CHECK-NEXT:     } body {
+// CHECK-NEXT:       cir.break
+// CHECK-NEXT:     ^bb1:  // no predecessors
+// CHECK-NEXT:       %1 = cir.const #cir.int<1> : !s32i
+// CHECK-NEXT:       cir.store %1, %0 : !s32i, !cir.ptr<!s32i>
+// CHECK-NEXT:       cir.yield
+// CHECK-NEXT:     } step {
+// CHECK-NEXT:       cir.yield
+// CHECK-NEXT:     }
+// CHECK-NEXT:   }
+// CHECK-NEXT:   cir.return
+// CHECK-NEXT: }
+
+void unreachable_after_continue() {
+  for (;;) {
+    continue;
+    int x = 1;
+  }
+}
+
+// CHECK-NEXT: cir.func @_Z26unreachable_after_continuev()
+// CHECK-NEXT:   cir.scope {
+// CHECK-NEXT:     %0 = cir.alloca !s32i, !cir.ptr<!s32i>, ["x", init] {alignment = 4 : i64}
+// CHECK-NEXT:     cir.for : cond {
+// CHECK-NEXT:       %1 = cir.const #true
+// CHECK-NEXT:       cir.condition(%1)
+// CHECK-NEXT:     } body {
+// CHECK-NEXT:       cir.continue
+// CHECK-NEXT:     ^bb1:  // no predecessors
+// CHECK-NEXT:       %1 = cir.const #cir.int<1> : !s32i
+// CHECK-NEXT:       cir.store %1, %0 : !s32i, !cir.ptr<!s32i>
+// CHECK-NEXT:       cir.yield
+// CHECK-NEXT:     } step {
+// CHECK-NEXT:       cir.yield
+// CHECK-NEXT:     }
+// CHECK-NEXT:   }
+// CHECK-NEXT:   cir.return
+// CHECK-NEXT: }

clang/test/CIR/CodeGen/return.cpp

@@ -12,3 +12,22 @@ int &ret0(int &x) {
 // CHECK:   cir.store %2, %1 : !cir.ptr<!s32i>, !cir.ptr<!cir.ptr<!s32i>>
 // CHECK:   %3 = cir.load %1 : !cir.ptr<!cir.ptr<!s32i>>, !cir.ptr<!s32i>
 // CHECK:   cir.return %3 : !cir.ptr<!s32i>
+
+int unreachable_after_return() {
+  return 0;
+  return 1;
+}
+
+// CHECK: cir.func @_Z24unreachable_after_returnv
+// CHECK-NEXT:   %0 = cir.alloca !s32i, !cir.ptr<!s32i>, ["__retval"] {alignment = 4 : i64}
+// CHECK-NEXT:   %1 = cir.const #cir.int<0> : !s32i
+// CHECK-NEXT:   cir.store %1, %0 : !s32i, !cir.ptr<!s32i>
+// CHECK-NEXT:   cir.br ^bb1
+// CHECK-NEXT: ^bb1:  // 2 preds: ^bb0, ^bb2
+// CHECK-NEXT:   %2 = cir.load %0 : !cir.ptr<!s32i>, !s32i
+// CHECK-NEXT:   cir.return %2 : !s32i
+// CHECK-NEXT: ^bb2:  // no predecessors
+// CHECK-NEXT:   %3 = cir.const #cir.int<1> : !s32i
+// CHECK-NEXT:   cir.store %3, %0 : !s32i, !cir.ptr<!s32i>
+// CHECK-NEXT:   cir.br ^bb1
+// CHECK-NEXT: }

clang/test/CIR/CodeGen/switch-unreachable-after-break.cpp

@@ -0,0 +1,22 @@
+// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck --input-file=%t.cir %s
+// XFAIL: *
+
+void unreachable_after_break(int a) {
+  switch(a) {
+  case 0:
+    break;
+    break;
+    int x = 1;
+  }
+}
+
+int unreachable_after_return(int a) {
+  switch (a) {
+  case 0:
+    return 0;
+    return 1;
+    int x = 1;
+  }
+  return 2;
+}

clang/test/CIR/CodeGen/switch.cpp

@@ -327,3 +327,23 @@ void fallthrough(int x) {
 // CHECK-NEXT:      }
 // CHECK-NEXT:      ]
 // CHECK-NEXT:    }
+
+int unreachable_after_break_1(int a) {
+  switch (a) {
+    case(42):
+      break;
+      goto exit;
+    default:
+      return 0;
+  };
+
+exit:
+  return -1;
+
+}
+// CHECK: cir.func @_Z25unreachable_after_break_1i
+// CHECK:   case (equal, 42) {
+// CHECK:     cir.break
+// CHECK:   ^bb1:  // no predecessors
+// CHECK:     cir.goto "exit"
+// CHECK:   }