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[CIR] Upstream support for coroutine co_yield expression #173162

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@Andres-Salamanca Andres-Salamanca commented Dec 20, 2025

This PR upstreams support for the co_yield expression by emitting a cir.await op with the yield kind.

@llvmbot llvmbot added clang Clang issues not falling into any other category ClangIR Anything related to the ClangIR project labels Dec 20, 2025
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llvmbot commented Dec 20, 2025

@llvm/pr-subscribers-clangir

Author: None (Andres-Salamanca)

Changes

This PR upstreams support for the co_yield expression by emitting a cir.await op with the yield kind.

Full diff: https://github.com/llvm/llvm-project/pull/173162.diff

5 Files Affected:

  • (modified) clang/include/clang/CIR/MissingFeatures.h (-1)
  • (modified) clang/lib/CIR/CodeGen/CIRGenCoroutine.cpp (+8-1)
  • (modified) clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp (+3-2)
  • (modified) clang/lib/CIR/CodeGen/CIRGenFunction.h (+4)
  • (modified) clang/test/CIR/CodeGen/coro-task.cpp (+50)
diff --git a/clang/include/clang/CIR/MissingFeatures.h b/clang/include/clang/CIR/MissingFeatures.h
index acfc937a11993..cc0d2579d176b 100644
--- a/clang/include/clang/CIR/MissingFeatures.h
+++ b/clang/include/clang/CIR/MissingFeatures.h
@@ -153,7 +153,6 @@ struct MissingFeatures {
   static bool emitBodyAndFallthrough() { return false; }
   static bool coroOutsideFrameMD() { return false; }
   static bool coroCoReturn() { return false; }
-  static bool coroCoYield() { return false; }
   static bool coroutineExceptions() { return false; };
 
   // Various handling of deferred processing in CIRGenModule.
diff --git a/clang/lib/CIR/CodeGen/CIRGenCoroutine.cpp b/clang/lib/CIR/CodeGen/CIRGenCoroutine.cpp
index 9251106a641b1..db3bdec436b94 100644
--- a/clang/lib/CIR/CodeGen/CIRGenCoroutine.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenCoroutine.cpp
@@ -418,7 +418,7 @@ emitSuspendExpression(CIRGenFunction &cgf, CGCoroData &coro,
         // FIXME(cir): the alloca for the resume expr should be placed in the
         // enclosing cir.scope instead.
         if (forLValue) {
-          assert(!cir::MissingFeatures::coroCoYield());
+          awaitRes.lv = cgf.emitLValue(s.getResumeExpr());
         } else {
           awaitRes.rv =
               cgf.emitAnyExpr(s.getResumeExpr(), aggSlot, ignoreResult);
@@ -486,6 +486,13 @@ RValue CIRGenFunction::emitCoawaitExpr(const CoawaitExpr &e,
                          ignoreResult);
 }
 
+RValue CIRGenFunction::emitCoyieldExpr(const CoyieldExpr &e,
+                                       AggValueSlot aggSlot,
+                                       bool ignoreResult) {
+  return emitSuspendExpr(*this, e, cir::AwaitKind::Yield, aggSlot,
+                         ignoreResult);
+}
+
 mlir::LogicalResult CIRGenFunction::emitCoreturnStmt(CoreturnStmt const &s) {
   ++curCoro.data->coreturnCount;
   curLexScope->setCoreturn();
diff --git a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
index 60884aefbfb1f..210e13af7eb35 100644
--- a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
@@ -165,10 +165,11 @@ class ScalarExprEmitter : public StmtVisitor<ScalarExprEmitter, mlir::Value> {
   mlir::Value VisitCoawaitExpr(CoawaitExpr *s) {
     return cgf.emitCoawaitExpr(*s).getValue();
   }
+
   mlir::Value VisitCoyieldExpr(CoyieldExpr *e) {
-    cgf.cgm.errorNYI(e->getSourceRange(), "ScalarExprEmitter: coyield");
-    return {};
+    return cgf.emitCoyieldExpr(*e).getValue();
   }
+
   mlir::Value VisitUnaryCoawait(const UnaryOperator *e) {
     cgf.cgm.errorNYI(e->getSourceRange(), "ScalarExprEmitter: unary coawait");
     return {};
diff --git a/clang/lib/CIR/CodeGen/CIRGenFunction.h b/clang/lib/CIR/CodeGen/CIRGenFunction.h
index 254a8c5883d48..5c178c9265bb2 100644
--- a/clang/lib/CIR/CodeGen/CIRGenFunction.h
+++ b/clang/lib/CIR/CodeGen/CIRGenFunction.h
@@ -1656,6 +1656,10 @@ class CIRGenFunction : public CIRGenTypeCache {
   RValue emitCoawaitExpr(const CoawaitExpr &e,
                          AggValueSlot aggSlot = AggValueSlot::ignored(),
                          bool ignoreResult = false);
+
+  RValue emitCoyieldExpr(const CoyieldExpr &e,
+                         AggValueSlot aggSlot = AggValueSlot::ignored(),
+                         bool ignoreResult = false);
   /// Emit the computation of the specified expression of complex type,
   /// returning the result.
   mlir::Value emitComplexExpr(const Expr *e);
diff --git a/clang/test/CIR/CodeGen/coro-task.cpp b/clang/test/CIR/CodeGen/coro-task.cpp
index 6cd494317f2d8..d7b06e1f61aa7 100644
--- a/clang/test/CIR/CodeGen/coro-task.cpp
+++ b/clang/test/CIR/CodeGen/coro-task.cpp
@@ -322,3 +322,53 @@ folly::coro::Task<void> silly_coro() {
 // CIR: cir.call @_ZN5folly4coro4TaskIvE12promise_type11return_voidEv
 // CIR-NOT: cir.call @_ZN5folly4coro4TaskIvE12promise_type11return_voidEv
 // CIR: cir.await(final, ready : {
+
+
+folly::coro::Task<void> yield();
+folly::coro::Task<void> yield1() {
+  auto t = yield();
+  co_yield t;
+}
+
+// CHECK: cir.func coroutine {{.*}} @_Z6yield1v() -> !rec_folly3A3Acoro3A3ATask3Cvoid3E
+
+// CIR: cir.await(init, ready : {
+// CIR: }, suspend : {
+// CIR: }, resume : {
+// CIR: },)
+
+//      CIR:  cir.scope {
+// CIR-NEXT:   %[[SUSPEND_PTR:.*]] = cir.alloca ![[SuspendAlways]], !cir.ptr<![[SuspendAlways]]>
+// CIR-NEXT:   %[[AWAITER_PTR:.*]] = cir.alloca ![[VoidTask]], !cir.ptr<![[VoidTask]]>
+// CIR-NEXT:   %[[CORO_PTR:.*]] = cir.alloca ![[CoroHandleVoid]], !cir.ptr<![[CoroHandleVoid]]>
+// CIR-NEXT:   %[[CORO2_PTR:.*]] = cir.alloca ![[CoroHandlePromiseVoid]], !cir.ptr<![[CoroHandlePromiseVoid]]>
+// CIR-NEXT:   cir.copy {{.*}} to %[[AWAITER_PTR]] : !cir.ptr<![[VoidTask]]>
+// CIR-NEXT:   %[[AWAITER:.*]] = cir.load{{.*}} %[[AWAITER_PTR]] : !cir.ptr<![[VoidTask]]>, ![[VoidTask]]
+// CIR-NEXT:   %[[SUSPEND:.*]] = cir.call @_ZN5folly4coro4TaskIvE12promise_type11yield_valueES2_(%{{.+}}, %[[AWAITER]]) nothrow : (!cir.ptr<![[VoidPromisse]]>, ![[VoidTask]]) -> ![[SuspendAlways]]
+// CIR-NEXT:   cir.store{{.*}} %[[SUSPEND]], %[[SUSPEND_PTR]] : ![[SuspendAlways]], !cir.ptr<![[SuspendAlways]]>
+// CIR-NEXT:   cir.await(yield, ready : {
+// CIR-NEXT:     %[[READY:.*]] = cir.scope {
+// CIR-NEXT:       %[[A:.*]] = cir.call @_ZNSt14suspend_always11await_readyEv(%[[SUSPEND_PTR]]) nothrow : (!cir.ptr<![[SuspendAlways]]>) -> !cir.bool
+// CIR-NEXT:       cir.yield %[[A]] : !cir.bool
+// CIR-NEXT:     } : !cir.bool
+// CIR-NEXT:     cir.condition(%[[READY]])
+// CIR-NEXT:   }, suspend : {
+// CIR-NEXT:     %[[CORO2:.*]] = cir.call @_ZNSt16coroutine_handleIN5folly4coro4TaskIvE12promise_typeEE12from_addressEPv(%9) nothrow : (!cir.ptr<!void>) -> ![[CoroHandlePromiseVoid]]
+// CIR-NEXT:     cir.store{{.*}} %[[CORO2]], %[[CORO2_PTR]] : ![[CoroHandlePromiseVoid]], !cir.ptr<![[CoroHandlePromiseVoid]]>
+// CIR-NEXT:     %[[B:.*]] = cir.load{{.*}} %[[CORO2_PTR]] : !cir.ptr<![[CoroHandlePromiseVoid]]>, ![[CoroHandlePromiseVoid]]
+// CIR-NEXT:     cir.call @_ZNSt16coroutine_handleIvEC1IN5folly4coro4TaskIvE12promise_typeEEES_IT_E(%[[CORO_PTR]], %[[B]]) nothrow : (!cir.ptr<![[CoroHandleVoid]]>, ![[CoroHandlePromiseVoid]]) -> ()
+// CIR-NEXT:     %[[C:.*]] = cir.load{{.*}} %[[CORO_PTR]] : !cir.ptr<![[CoroHandleVoid]]>, ![[CoroHandleVoid]]
+// CIR-NEXT:     cir.call @_ZNSt14suspend_always13await_suspendESt16coroutine_handleIvE(%[[SUSPEND_PTR]], %[[C]]) nothrow : (!cir.ptr<![[SuspendAlways]]>, ![[CoroHandleVoid]]) -> ()
+// CIR-NEXT:     cir.yield
+// CIR-NEXT:   }, resume : {
+// CIR-NEXT:     cir.call @_ZNSt14suspend_always12await_resumeEv(%[[SUSPEND_PTR]]) nothrow : (!cir.ptr<![[SuspendAlways]]>) -> ()
+// CIR-NEXT:     cir.yield
+// CIR-NEXT:   },)
+// CIR-NEXT: }
+
+// CIR: cir.await(final, ready : {
+// CIR: }, suspend : {
+// CIR: }, resume : {
+// CIR: },)
+
+// CHECK: }

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llvmbot commented Dec 20, 2025

@llvm/pr-subscribers-clang

Author: None (Andres-Salamanca)

Changes

This PR upstreams support for the co_yield expression by emitting a cir.await op with the yield kind.

Full diff: https://github.com/llvm/llvm-project/pull/173162.diff

5 Files Affected:

  • (modified) clang/include/clang/CIR/MissingFeatures.h (-1)
  • (modified) clang/lib/CIR/CodeGen/CIRGenCoroutine.cpp (+8-1)
  • (modified) clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp (+3-2)
  • (modified) clang/lib/CIR/CodeGen/CIRGenFunction.h (+4)
  • (modified) clang/test/CIR/CodeGen/coro-task.cpp (+50)
diff --git a/clang/include/clang/CIR/MissingFeatures.h b/clang/include/clang/CIR/MissingFeatures.h
index acfc937a11993..cc0d2579d176b 100644
--- a/clang/include/clang/CIR/MissingFeatures.h
+++ b/clang/include/clang/CIR/MissingFeatures.h
@@ -153,7 +153,6 @@ struct MissingFeatures {
   static bool emitBodyAndFallthrough() { return false; }
   static bool coroOutsideFrameMD() { return false; }
   static bool coroCoReturn() { return false; }
-  static bool coroCoYield() { return false; }
   static bool coroutineExceptions() { return false; };
 
   // Various handling of deferred processing in CIRGenModule.
diff --git a/clang/lib/CIR/CodeGen/CIRGenCoroutine.cpp b/clang/lib/CIR/CodeGen/CIRGenCoroutine.cpp
index 9251106a641b1..db3bdec436b94 100644
--- a/clang/lib/CIR/CodeGen/CIRGenCoroutine.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenCoroutine.cpp
@@ -418,7 +418,7 @@ emitSuspendExpression(CIRGenFunction &cgf, CGCoroData &coro,
         // FIXME(cir): the alloca for the resume expr should be placed in the
         // enclosing cir.scope instead.
         if (forLValue) {
-          assert(!cir::MissingFeatures::coroCoYield());
+          awaitRes.lv = cgf.emitLValue(s.getResumeExpr());
         } else {
           awaitRes.rv =
               cgf.emitAnyExpr(s.getResumeExpr(), aggSlot, ignoreResult);
@@ -486,6 +486,13 @@ RValue CIRGenFunction::emitCoawaitExpr(const CoawaitExpr &e,
                          ignoreResult);
 }
 
+RValue CIRGenFunction::emitCoyieldExpr(const CoyieldExpr &e,
+                                       AggValueSlot aggSlot,
+                                       bool ignoreResult) {
+  return emitSuspendExpr(*this, e, cir::AwaitKind::Yield, aggSlot,
+                         ignoreResult);
+}
+
 mlir::LogicalResult CIRGenFunction::emitCoreturnStmt(CoreturnStmt const &s) {
   ++curCoro.data->coreturnCount;
   curLexScope->setCoreturn();
diff --git a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
index 60884aefbfb1f..210e13af7eb35 100644
--- a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
@@ -165,10 +165,11 @@ class ScalarExprEmitter : public StmtVisitor<ScalarExprEmitter, mlir::Value> {
   mlir::Value VisitCoawaitExpr(CoawaitExpr *s) {
     return cgf.emitCoawaitExpr(*s).getValue();
   }
+
   mlir::Value VisitCoyieldExpr(CoyieldExpr *e) {
-    cgf.cgm.errorNYI(e->getSourceRange(), "ScalarExprEmitter: coyield");
-    return {};
+    return cgf.emitCoyieldExpr(*e).getValue();
   }
+
   mlir::Value VisitUnaryCoawait(const UnaryOperator *e) {
     cgf.cgm.errorNYI(e->getSourceRange(), "ScalarExprEmitter: unary coawait");
     return {};
diff --git a/clang/lib/CIR/CodeGen/CIRGenFunction.h b/clang/lib/CIR/CodeGen/CIRGenFunction.h
index 254a8c5883d48..5c178c9265bb2 100644
--- a/clang/lib/CIR/CodeGen/CIRGenFunction.h
+++ b/clang/lib/CIR/CodeGen/CIRGenFunction.h
@@ -1656,6 +1656,10 @@ class CIRGenFunction : public CIRGenTypeCache {
   RValue emitCoawaitExpr(const CoawaitExpr &e,
                          AggValueSlot aggSlot = AggValueSlot::ignored(),
                          bool ignoreResult = false);
+
+  RValue emitCoyieldExpr(const CoyieldExpr &e,
+                         AggValueSlot aggSlot = AggValueSlot::ignored(),
+                         bool ignoreResult = false);
   /// Emit the computation of the specified expression of complex type,
   /// returning the result.
   mlir::Value emitComplexExpr(const Expr *e);
diff --git a/clang/test/CIR/CodeGen/coro-task.cpp b/clang/test/CIR/CodeGen/coro-task.cpp
index 6cd494317f2d8..d7b06e1f61aa7 100644
--- a/clang/test/CIR/CodeGen/coro-task.cpp
+++ b/clang/test/CIR/CodeGen/coro-task.cpp
@@ -322,3 +322,53 @@ folly::coro::Task<void> silly_coro() {
 // CIR: cir.call @_ZN5folly4coro4TaskIvE12promise_type11return_voidEv
 // CIR-NOT: cir.call @_ZN5folly4coro4TaskIvE12promise_type11return_voidEv
 // CIR: cir.await(final, ready : {
+
+
+folly::coro::Task<void> yield();
+folly::coro::Task<void> yield1() {
+  auto t = yield();
+  co_yield t;
+}
+
+// CHECK: cir.func coroutine {{.*}} @_Z6yield1v() -> !rec_folly3A3Acoro3A3ATask3Cvoid3E
+
+// CIR: cir.await(init, ready : {
+// CIR: }, suspend : {
+// CIR: }, resume : {
+// CIR: },)
+
+//      CIR:  cir.scope {
+// CIR-NEXT:   %[[SUSPEND_PTR:.*]] = cir.alloca ![[SuspendAlways]], !cir.ptr<![[SuspendAlways]]>
+// CIR-NEXT:   %[[AWAITER_PTR:.*]] = cir.alloca ![[VoidTask]], !cir.ptr<![[VoidTask]]>
+// CIR-NEXT:   %[[CORO_PTR:.*]] = cir.alloca ![[CoroHandleVoid]], !cir.ptr<![[CoroHandleVoid]]>
+// CIR-NEXT:   %[[CORO2_PTR:.*]] = cir.alloca ![[CoroHandlePromiseVoid]], !cir.ptr<![[CoroHandlePromiseVoid]]>
+// CIR-NEXT:   cir.copy {{.*}} to %[[AWAITER_PTR]] : !cir.ptr<![[VoidTask]]>
+// CIR-NEXT:   %[[AWAITER:.*]] = cir.load{{.*}} %[[AWAITER_PTR]] : !cir.ptr<![[VoidTask]]>, ![[VoidTask]]
+// CIR-NEXT:   %[[SUSPEND:.*]] = cir.call @_ZN5folly4coro4TaskIvE12promise_type11yield_valueES2_(%{{.+}}, %[[AWAITER]]) nothrow : (!cir.ptr<![[VoidPromisse]]>, ![[VoidTask]]) -> ![[SuspendAlways]]
+// CIR-NEXT:   cir.store{{.*}} %[[SUSPEND]], %[[SUSPEND_PTR]] : ![[SuspendAlways]], !cir.ptr<![[SuspendAlways]]>
+// CIR-NEXT:   cir.await(yield, ready : {
+// CIR-NEXT:     %[[READY:.*]] = cir.scope {
+// CIR-NEXT:       %[[A:.*]] = cir.call @_ZNSt14suspend_always11await_readyEv(%[[SUSPEND_PTR]]) nothrow : (!cir.ptr<![[SuspendAlways]]>) -> !cir.bool
+// CIR-NEXT:       cir.yield %[[A]] : !cir.bool
+// CIR-NEXT:     } : !cir.bool
+// CIR-NEXT:     cir.condition(%[[READY]])
+// CIR-NEXT:   }, suspend : {
+// CIR-NEXT:     %[[CORO2:.*]] = cir.call @_ZNSt16coroutine_handleIN5folly4coro4TaskIvE12promise_typeEE12from_addressEPv(%9) nothrow : (!cir.ptr<!void>) -> ![[CoroHandlePromiseVoid]]
+// CIR-NEXT:     cir.store{{.*}} %[[CORO2]], %[[CORO2_PTR]] : ![[CoroHandlePromiseVoid]], !cir.ptr<![[CoroHandlePromiseVoid]]>
+// CIR-NEXT:     %[[B:.*]] = cir.load{{.*}} %[[CORO2_PTR]] : !cir.ptr<![[CoroHandlePromiseVoid]]>, ![[CoroHandlePromiseVoid]]
+// CIR-NEXT:     cir.call @_ZNSt16coroutine_handleIvEC1IN5folly4coro4TaskIvE12promise_typeEEES_IT_E(%[[CORO_PTR]], %[[B]]) nothrow : (!cir.ptr<![[CoroHandleVoid]]>, ![[CoroHandlePromiseVoid]]) -> ()
+// CIR-NEXT:     %[[C:.*]] = cir.load{{.*}} %[[CORO_PTR]] : !cir.ptr<![[CoroHandleVoid]]>, ![[CoroHandleVoid]]
+// CIR-NEXT:     cir.call @_ZNSt14suspend_always13await_suspendESt16coroutine_handleIvE(%[[SUSPEND_PTR]], %[[C]]) nothrow : (!cir.ptr<![[SuspendAlways]]>, ![[CoroHandleVoid]]) -> ()
+// CIR-NEXT:     cir.yield
+// CIR-NEXT:   }, resume : {
+// CIR-NEXT:     cir.call @_ZNSt14suspend_always12await_resumeEv(%[[SUSPEND_PTR]]) nothrow : (!cir.ptr<![[SuspendAlways]]>) -> ()
+// CIR-NEXT:     cir.yield
+// CIR-NEXT:   },)
+// CIR-NEXT: }
+
+// CIR: cir.await(final, ready : {
+// CIR: }, suspend : {
+// CIR: }, resume : {
+// CIR: },)
+
+// CHECK: }

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github-actions bot commented Dec 20, 2025

🪟 Windows x64 Test Results

  • 53117 tests passed
  • 2526 tests skipped
  • 1 test failed

Failed Tests

(click on a test name to see its output)

AddressSanitizer-Unit

AddressSanitizer-Unit._/Asan-x86_64-calls-Test_exe/AddressSanitizerInterface/GetHeapSizeTest 
Script:
--
C:\_work\llvm-project\llvm-project\build\runtimes\runtimes-bins\compiler-rt\lib\asan\tests\X86_64WindowsConfig\.\Asan-x86_64-calls-Test.exe --gtest_filter=AddressSanitizerInterface.GetHeapSizeTest
--
C:/_work/llvm-project/llvm-project/compiler-rt/lib/asan/tests/asan_interface_test.cpp:100
Expected equality of these values:
  old_heap_size
    Which is: 12066816
  __sanitizer_get_heap_size()
    Which is: 12591104

C:/_work/llvm-project/llvm-project/compiler-rt/lib/asan/tests/asan_interface_test.cpp:100
Expected equality of these values:
  old_heap_size
    Which is: 12066816
  __sanitizer_get_heap_size()
    Which is: 12591104

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the infrastructure label.

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