[CIR] Add bit reverse and byte reverse operations (llvm#147200)

Lancern · web-flow · commit 265fb3605d1d · 2025-07-12T12:15:36.000+08:00
This patch adds support for the following two builtin functions:

- `__builtin_bswap`, represented by the `cir.byte_swap` operation.
- `__builtin_bitreverse`, represented by the `cir.bit.reverse`
operation.
diff --git a/clang/include/clang/CIR/Dialect/IR/CIROps.td b/clang/include/clang/CIR/Dialect/IR/CIROps.td
@@ -2808,6 +2808,45 @@ def BitPopcountOp : CIR_BitOpBase<"bit.popcnt",
   }];
 }
 
+def BitReverseOp : CIR_BitOpBase<"bit.reverse",
+                                 CIR_UIntOfWidths<[8, 16, 32, 64]>> {
+  let summary = "Reverse the bit pattern of the operand integer";
+  let description = [{
+    The `cir.bit.reverse` operation reverses the bits of the operand integer.
+    Its only argument must be of unsigned integer types of width 8, 16, 32, or
+    64.
+
+    This operation covers the C/C++ builtin function `__builtin_bitreverse`.
+
+    Example:
+
+    ```mlir
+    %1 = cir.bit.reverse(%0 : !u32i): !u32i
+    ```
+  }];
+}
+
+def ByteSwapOp : CIR_BitOpBase<"byte_swap", CIR_UIntOfWidths<[16, 32, 64]>> {
+  let summary = "Reverse the bytes in the object representation of the operand";
+  let description = [{
+    The `cir.byte_swap` operation takes an integer as operand, reverse the bytes
+    in the object representation of the operand integer, and returns the result.
+
+    The operand integer must be an unsigned integer. Its widths must be either
+    16, 32, or 64.
+
+    Example:
+
+    ```mlir
+    // %0 = 0x12345678
+    %0 = cir.const #cir.int<305419896> : !u32i
+
+    // %1 should be 0x78563412
+    %1 = cir.byte_swap(%0 : !u32i) : !u32i
+    ```
+  }];
+}
+
 //===----------------------------------------------------------------------===//
 // Assume Operations
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp b/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp
@@ -60,24 +60,23 @@ static RValue emitBuiltinBitOp(CIRGenFunction &cgf, const CallExpr *e,
 RValue CIRGenFunction::emitBuiltinExpr(const GlobalDecl &gd, unsigned builtinID,
                                        const CallExpr *e,
                                        ReturnValueSlot returnValue) {
+  mlir::Location loc = getLoc(e->getSourceRange());
+
   // See if we can constant fold this builtin.  If so, don't emit it at all.
   // TODO: Extend this handling to all builtin calls that we can constant-fold.
   Expr::EvalResult result;
   if (e->isPRValue() && e->EvaluateAsRValue(result, cgm.getASTContext()) &&
       !result.hasSideEffects()) {
-    if (result.Val.isInt()) {
-      return RValue::get(builder.getConstInt(getLoc(e->getSourceRange()),
-                                             result.Val.getInt()));
-    }
+    if (result.Val.isInt())
+      return RValue::get(builder.getConstInt(loc, result.Val.getInt()));
     if (result.Val.isFloat()) {
       // Note: we are using result type of CallExpr to determine the type of
       // the constant. Classic codegen uses the result value to determine the
       // type. We feel it should be Ok to use expression type because it is
       // hard to imagine a builtin function evaluates to a value that
       // over/underflows its own defined type.
       mlir::Type type = convertType(e->getType());
-      return RValue::get(builder.getConstFP(getLoc(e->getExprLoc()), type,
-                                            result.Val.getFloat()));
+      return RValue::get(builder.getConstFP(loc, type, result.Val.getFloat()));
     }
   }
 
@@ -94,8 +93,6 @@ RValue CIRGenFunction::emitBuiltinExpr(const GlobalDecl &gd, unsigned builtinID,
   assert(!cir::MissingFeatures::builtinCallMathErrno());
   assert(!cir::MissingFeatures::builtinCall());
 
-  mlir::Location loc = getLoc(e->getExprLoc());
-
   switch (builtinIDIfNoAsmLabel) {
   default:
     break;
@@ -200,11 +197,28 @@ RValue CIRGenFunction::emitBuiltinExpr(const GlobalDecl &gd, unsigned builtinID,
                                       probability);
     }
 
-    auto result = builder.create<cir::ExpectOp>(getLoc(e->getSourceRange()),
-                                                argValue.getType(), argValue,
-                                                expectedValue, probAttr);
+    auto result = builder.create<cir::ExpectOp>(
+        loc, argValue.getType(), argValue, expectedValue, probAttr);
     return RValue::get(result);
   }
+
+  case Builtin::BI__builtin_bswap16:
+  case Builtin::BI__builtin_bswap32:
+  case Builtin::BI__builtin_bswap64:
+  case Builtin::BI_byteswap_ushort:
+  case Builtin::BI_byteswap_ulong:
+  case Builtin::BI_byteswap_uint64: {
+    mlir::Value arg = emitScalarExpr(e->getArg(0));
+    return RValue::get(builder.create<cir::ByteSwapOp>(loc, arg));
+  }
+
+  case Builtin::BI__builtin_bitreverse8:
+  case Builtin::BI__builtin_bitreverse16:
+  case Builtin::BI__builtin_bitreverse32:
+  case Builtin::BI__builtin_bitreverse64: {
+    mlir::Value arg = emitScalarExpr(e->getArg(0));
+    return RValue::get(builder.create<cir::BitReverseOp>(loc, arg));
+  }
   }
 
   // If this is an alias for a lib function (e.g. __builtin_sin), emit
diff --git a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
@@ -535,6 +535,13 @@ mlir::LogicalResult CIRToLLVMBitPopcountOpLowering::matchAndRewrite(
   return mlir::LogicalResult::success();
 }
 
+mlir::LogicalResult CIRToLLVMBitReverseOpLowering::matchAndRewrite(
+    cir::BitReverseOp op, OpAdaptor adaptor,
+    mlir::ConversionPatternRewriter &rewriter) const {
+  rewriter.replaceOpWithNewOp<mlir::LLVM::BitReverseOp>(op, adaptor.getInput());
+  return mlir::success();
+}
+
 mlir::LogicalResult CIRToLLVMBrCondOpLowering::matchAndRewrite(
     cir::BrCondOp brOp, OpAdaptor adaptor,
     mlir::ConversionPatternRewriter &rewriter) const {
@@ -551,6 +558,13 @@ mlir::LogicalResult CIRToLLVMBrCondOpLowering::matchAndRewrite(
   return mlir::success();
 }
 
+mlir::LogicalResult CIRToLLVMByteSwapOpLowering::matchAndRewrite(
+    cir::ByteSwapOp op, OpAdaptor adaptor,
+    mlir::ConversionPatternRewriter &rewriter) const {
+  rewriter.replaceOpWithNewOp<mlir::LLVM::ByteSwapOp>(op, adaptor.getInput());
+  return mlir::LogicalResult::success();
+}
+
 mlir::Type CIRToLLVMCastOpLowering::convertTy(mlir::Type ty) const {
   return getTypeConverter()->convertType(ty);
 }
@@ -2044,8 +2058,10 @@ void ConvertCIRToLLVMPass::runOnOperation() {
                CIRToLLVMBitCtzOpLowering,
                CIRToLLVMBitParityOpLowering,
                CIRToLLVMBitPopcountOpLowering,
+               CIRToLLVMBitReverseOpLowering,
                CIRToLLVMBrCondOpLowering,
                CIRToLLVMBrOpLowering,
+               CIRToLLVMByteSwapOpLowering,
                CIRToLLVMCallOpLowering,
                CIRToLLVMCmpOpLowering,
                CIRToLLVMComplexAddOpLowering,
diff --git a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.h b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.h
@@ -94,6 +94,16 @@ class CIRToLLVMBitPopcountOpLowering
                   mlir::ConversionPatternRewriter &) const override;
 };
 
+class CIRToLLVMBitReverseOpLowering
+    : public mlir::OpConversionPattern<cir::BitReverseOp> {
+public:
+  using mlir::OpConversionPattern<cir::BitReverseOp>::OpConversionPattern;
+
+  mlir::LogicalResult
+  matchAndRewrite(cir::BitReverseOp op, OpAdaptor,
+                  mlir::ConversionPatternRewriter &) const override;
+};
+
 class CIRToLLVMBrCondOpLowering
     : public mlir::OpConversionPattern<cir::BrCondOp> {
 public:
@@ -104,6 +114,16 @@ class CIRToLLVMBrCondOpLowering
                   mlir::ConversionPatternRewriter &) const override;
 };
 
+class CIRToLLVMByteSwapOpLowering
+    : public mlir::OpConversionPattern<cir::ByteSwapOp> {
+public:
+  using mlir::OpConversionPattern<cir::ByteSwapOp>::OpConversionPattern;
+
+  mlir::LogicalResult
+  matchAndRewrite(cir::ByteSwapOp op, OpAdaptor,
+                  mlir::ConversionPatternRewriter &) const override;
+};
+
 class CIRToLLVMCastOpLowering : public mlir::OpConversionPattern<cir::CastOp> {
   mlir::DataLayout const &dataLayout;
 
diff --git a/clang/test/CIR/CodeGen/builtin_bit.cpp b/clang/test/CIR/CodeGen/builtin_bit.cpp
@@ -325,3 +325,94 @@ int test_builtin_popcountg(unsigned x) {
 
 // OGCG-LABEL: _Z22test_builtin_popcountgj
 // OGCG:         %{{.+}} = call i32 @llvm.ctpop.i32(i32 %{{.+}})
+
+unsigned char test_builtin_bitreverse8(unsigned char x) {
+  return __builtin_bitreverse8(x);
+}
+
+// CIR-LABEL: @_Z24test_builtin_bitreverse8h
+// CIR:         %{{.+}} = cir.bit.reverse(%{{.+}} : !u8i) : !u8i
+
+// LLVM-LABEL: @_Z24test_builtin_bitreverse8h
+// LLVM:         %{{.+}} = call i8 @llvm.bitreverse.i8(i8 %{{.+}})
+
+// OGCG-LABEL: @_Z24test_builtin_bitreverse8h
+// OGCG:         %{{.+}} = call i8 @llvm.bitreverse.i8(i8 %{{.+}})
+
+unsigned short test_builtin_bitreverse16(unsigned short x) {
+  return __builtin_bitreverse16(x);
+}
+
+// CIR-LABEL: @_Z25test_builtin_bitreverse16t
+// CIR:         %{{.+}} = cir.bit.reverse(%{{.+}} : !u16i) : !u16i
+
+// LLVM-LABEL: @_Z25test_builtin_bitreverse16t
+// LLVM:         %{{.+}} = call i16 @llvm.bitreverse.i16(i16 %{{.+}})
+
+// OGCG-LABEL: @_Z25test_builtin_bitreverse16t
+// OGCG:         %{{.+}} = call i16 @llvm.bitreverse.i16(i16 %{{.+}})
+
+unsigned test_builtin_bitreverse32(unsigned x) {
+  return __builtin_bitreverse32(x);
+}
+
+// CIR-LABEL: @_Z25test_builtin_bitreverse32j
+// CIR:         %{{.+}} = cir.bit.reverse(%{{.+}} : !u32i) : !u32i
+
+// LLVM-LABEL: @_Z25test_builtin_bitreverse32j
+// LLVM:         %{{.+}} = call i32 @llvm.bitreverse.i32(i32 %{{.+}})
+
+// OGCG-LABEL: @_Z25test_builtin_bitreverse32j
+// OGCG:         %{{.+}} = call i32 @llvm.bitreverse.i32(i32 %{{.+}})
+
+unsigned long long test_builtin_bitreverse64(unsigned long long x) {
+  return __builtin_bitreverse64(x);
+}
+
+// CIR-LABEL: @_Z25test_builtin_bitreverse64y
+// CIR:         %{{.+}} = cir.bit.reverse(%{{.+}} : !u64i) : !u64i
+
+// LLVM-LABEL: @_Z25test_builtin_bitreverse64y
+// LLVM:         %{{.+}} = call i64 @llvm.bitreverse.i64(i64 %{{.+}})
+
+// OGCG-LABEL: @_Z25test_builtin_bitreverse64y
+// OGCG:         %{{.+}} = call i64 @llvm.bitreverse.i64(i64 %{{.+}})
+
+unsigned short test_builtin_bswap16(unsigned short x) {
+  return __builtin_bswap16(x);
+}
+
+// CIR-LABEL: @_Z20test_builtin_bswap16t
+// CIR:         %{{.+}} = cir.byte_swap(%{{.+}} : !u16i) : !u16i
+
+// LLVM-LABEL: @_Z20test_builtin_bswap16t
+// LLVM:         %{{.+}} = call i16 @llvm.bswap.i16(i16 %{{.+}})
+
+// OGCG-LABEL: @_Z20test_builtin_bswap16t
+// OGCG:         %{{.+}} = call i16 @llvm.bswap.i16(i16 %{{.+}})
+
+unsigned test_builtin_bswap32(unsigned x) {
+  return __builtin_bswap32(x);
+}
+
+// CIR-LABEL: @_Z20test_builtin_bswap32j
+// CIR:         %{{.+}} = cir.byte_swap(%{{.+}} : !u32i) : !u32i
+
+// LLVM-LABEL: @_Z20test_builtin_bswap32j
+// LLVM:         %{{.+}} = call i32 @llvm.bswap.i32(i32 %{{.+}})
+
+// OGCG-LABEL: @_Z20test_builtin_bswap32j
+// OGCG:         %{{.+}} = call i32 @llvm.bswap.i32(i32 %{{.+}})
+
+unsigned long long test_builtin_bswap64(unsigned long long x) {
+  return __builtin_bswap64(x);
+}
+
+// CIR-LABEL: @_Z20test_builtin_bswap64y
+// CIR:         %{{.+}} = cir.byte_swap(%{{.+}} : !u64i) : !u64i
+
+// LLVM-LABEL: @_Z20test_builtin_bswap64y
+// LLVM:         %{{.+}} = call i64 @llvm.bswap.i64(i64 %{{.+}})
+
+// OGCG-LABEL: @_Z20test_builtin_bswap64y
+// OGCG:         %{{.+}} = call i64 @llvm.bswap.i64(i64 %{{.+}})
