[clang] [CIR] Add support for binary operations on bitfield members (PR #149676)

[via cfe-commits]

https://github.com/Andres-Salamanca created https://github.com/llvm/llvm-project/pull/149676

This PR introduces support for binary operations on bitfield members.

>From c5da343296558a3a418c6282b104196d20f88a60 Mon Sep 17 00:00:00 2001
From: Andres Salamanca <andrealebarbaritos at gmail.com>
Date: Sat, 19 Jul 2025 15:54:56 -0500
Subject: [PATCH] [CIR] Add support for binary operations on bitfield members

---
 clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp |  2 +-
 clang/test/CIR/CodeGen/bitfields.c         | 48 ++++++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
index eba6bffbf2927..cf82d1d283058 100644
--- a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
@@ -1125,7 +1125,7 @@ LValue ScalarExprEmitter::emitCompoundAssignLValue(
   // 'An assignment expression has the value of the left operand after the
   // assignment...'.
   if (lhsLV.isBitField())
-    cgf.cgm.errorNYI(e->getSourceRange(), "store through bitfield lvalue");
+    cgf.emitStoreThroughBitfieldLValue(RValue::get(result), lhsLV);
   else
     cgf.emitStoreThroughLValue(RValue::get(result), lhsLV);
 
diff --git a/clang/test/CIR/CodeGen/bitfields.c b/clang/test/CIR/CodeGen/bitfields.c
index a73c076ea81ab..869a7c98e2569 100644
--- a/clang/test/CIR/CodeGen/bitfields.c
+++ b/clang/test/CIR/CodeGen/bitfields.c
@@ -315,3 +315,51 @@ void unOp(S* s) {
 // OGCG:   [[TMP12:%.*]] = shl i64 [[TMP8]], 62
 // OGCG:   [[TMP13:%.*]] = ashr i64 [[TMP12]], 62
 // OGCG:   [[TMP14:%.*]] = trunc i64 [[TMP13]] to i32
+
+void binOp(S* s) {
+   s->d |= 42;
+}
+
+// CIR: cir.func {{.*@binOp}}
+// CIR:   [[TMP0:%.*]] = cir.const #cir.int<42> : !s32i
+// CIR:   [[TMP1:%.*]] = cir.get_member {{.*}}[0] {name = "d"} : !cir.ptr<!rec_S> -> !cir.ptr<!u64i>
+// CIR:   [[TMP2:%.*]] = cir.get_bitfield align(4) (#bfi_d, [[TMP1]] : !cir.ptr<!u64i>) -> !s32i
+// CIR:   [[TMP3:%.*]] = cir.binop(or, [[TMP2]], [[TMP0]]) : !s32i
+// CIR:   cir.set_bitfield align(4) (#bfi_d, [[TMP1]] : !cir.ptr<!u64i>, [[TMP3]] : !s32i)
+
+// LLVM: define {{.*@binOp}}
+// LLVM:   [[TMP0:%.*]] = load ptr, ptr {{.*}}, align 8
+// LLVM:   [[TMP1:%.*]] = getelementptr %struct.S, ptr [[TMP0]], i32 0, i32 0
+// LLVM:   [[TMP2:%.*]] = load i64, ptr [[TMP1]], align 4
+// LLVM:   [[TMP3:%.*]] = shl i64 [[TMP2]], 13
+// LLVM:   [[TMP4:%.*]] = ashr i64 [[TMP3]], 62
+// LLVM:   [[TMP5:%.*]] = trunc i64 [[TMP4]] to i32
+// LLVM:   [[TMP6:%.*]] = or i32 [[TMP5]], 42
+// LLVM:   [[TMP7:%.*]] = zext i32 [[TMP6]] to i64
+// LLVM:   [[TMP8:%.*]] = load i64, ptr [[TMP1]], align 4
+// LLVM:   [[TMP9:%.*]] = and i64 [[TMP7]], 3
+// LLVM:   [[TMP10:%.*]] = shl i64 [[TMP9]], 49
+// LLVM:   [[TMP11:%.*]] = and i64 [[TMP8]], -1688849860263937
+// LLVM:   [[TMP12:%.*]] = or i64 [[TMP11]], [[TMP10]]
+// LLVM:   store i64 [[TMP12]], ptr [[TMP1]], align 4
+// LLVM:   [[TMP13:%.*]] = shl i64 [[TMP9]], 62
+// LLVM:   [[TMP14:%.*]] = ashr i64 [[TMP13]], 62
+// LLVM:   [[TMP15:%.*]] = trunc i64 [[TMP14]] to i32
+
+// OGCG: define {{.*@binOp}}
+// OGCG:   [[TMP0:%.*]] = load ptr, ptr %s.addr, align 8
+// OGCG:   [[TMP1:%.*]] = load i64, ptr [[TMP0]], align 4
+// OGCG:   [[TMP2:%.*]] = shl i64 [[TMP1]], 13
+// OGCG:   [[TMP3:%.*]] = ashr i64 [[TMP2]], 62
+// OGCG:   [[TMP4:%.*]] = trunc i64 [[TMP3]] to i32
+// OGCG:   [[TMP5:%.*]] = or i32 [[TMP4]], 42
+// OGCG:   [[TMP6:%.*]] = zext i32 [[TMP5]] to i64
+// OGCG:   [[TMP7:%.*]] = load i64, ptr [[TMP0]], align 4
+// OGCG:   [[TMP8:%.*]] = and i64 [[TMP6]], 3
+// OGCG:   [[TMP9:%.*]] = shl i64 [[TMP8]], 49
+// OGCG:   [[TMP10:%.*]] = and i64 [[TMP7]], -1688849860263937
+// OGCG:   [[TMP11:%.*]] = or i64 [[TMP10]], [[TMP9]]
+// OGCG:   store i64 [[TMP11]], ptr [[TMP0]], align 4
+// OGCG:   [[TMP12:%.*]] = shl i64 [[TMP8]], 62
+// OGCG:   [[TMP13:%.*]] = ashr i64 [[TMP12]], 62
+// OGCG:   [[TMP14:%.*]] = trunc i64 [[TMP13]] to i32