[clang] [CIR] Upstream handling for __builtin_prefetch (PR #164387)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Shawn K (kimsh02)

<details>
<summary>Changes</summary>

Fix #<!-- -->163886

---
Full diff: https://github.com/llvm/llvm-project/pull/164387.diff


4 Files Affected:

- (modified) clang/include/clang/CIR/Dialect/IR/CIROps.td (+33) 
- (modified) clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp (+21) 
- (modified) clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp (+9) 
- (added) clang/test/CIR/CodeGen/builtin_prefetech.c (+20) 


``````````diff
diff --git a/clang/include/clang/CIR/Dialect/IR/CIROps.td b/clang/include/clang/CIR/Dialect/IR/CIROps.td
index e0163a4fecd5f..43abdc8f7bc0b 100644
--- a/clang/include/clang/CIR/Dialect/IR/CIROps.td
+++ b/clang/include/clang/CIR/Dialect/IR/CIROps.td
@@ -4049,6 +4049,39 @@ def CIR_ExpectOp : CIR_Op<"expect", [
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// PrefetchOp
+//===----------------------------------------------------------------------===//
+
+def CIR_PrefetchOp : CIR_Op<"prefetch"> {
+  let summary = "prefetch operation";
+  let description = [{
+    The `cir.prefetch` op prefetches data from the memmory address.
+
+    ```mlir
+    cir.prefetch(%0 : !cir.ptr<!void>) locality(1) write
+    ```
+
+    This opcode has the three attributes:
+    1. The $locality is a temporal locality specifier
+    ranging from (0) - no locality, to (3) - extremely local keep in cache.
+    2. The $isWrite is the specifier determining if the prefetch is prepaired
+    for a 'read' or 'write'.
+    If $isWrite doesn't specified it means that prefetch is prepared for 'read'.
+  }];
+
+  let arguments = (ins CIR_VoidPtrType:$addr,
+      ConfinedAttr<I32Attr, [IntMinValue<0>, IntMaxValue<3>]>:$locality,
+      UnitAttr:$isWrite);
+
+  let assemblyFormat = [{
+    `(` $addr `:` qualified(type($addr)) `)`
+        `locality``(` $locality `)`
+        (`write` $isWrite^) : (`read`)?
+        attr-dict
+  }];
+}
+
 //===----------------------------------------------------------------------===//
 // PtrDiffOp
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp b/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp
index ea31871806bd7..2571a402f9676 100644
--- a/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp
@@ -454,6 +454,27 @@ RValue CIRGenFunction::emitBuiltinExpr(const GlobalDecl &gd, unsigned builtinID,
     assert(!cir::MissingFeatures::coroSizeBuiltinCall());
     return getUndefRValue(e->getType());
   }
+  case Builtin::BI__builtin_prefetch: {
+    auto evaluateOperandAsInt = [&](const Expr *arg) {
+      Expr::EvalResult res;
+      [[maybe_unused]] bool evalSucceed =
+          arg->EvaluateAsInt(res, cgm.getASTContext());
+      assert(evalSucceed && "expression should be able to evaluate as int");
+      return res.Val.getInt().getZExtValue();
+    };
+
+    bool isWrite = false;
+    if (e->getNumArgs() > 1)
+      isWrite = evaluateOperandAsInt(e->getArg(1));
+
+    int locality = 0;
+    if (e->getNumArgs() > 2)
+      locality = evaluateOperandAsInt(e->getArg(2));
+
+    mlir::Value address = emitScalarExpr(e->getArg(0));
+    cir::PrefetchOp::create(builder, loc, address, locality, isWrite);
+    return RValue::get(nullptr);
+  }
   }
 
   // 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
index 0243bf120f396..47f9d79b30655 100644
--- a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
+++ b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
@@ -1507,6 +1507,15 @@ static uint64_t getTypeSize(mlir::Type type, mlir::Operation &op) {
   return llvm::divideCeil(layout.getTypeSizeInBits(type), 8);
 }
 
+mlir::LogicalResult CIRToLLVMPrefetchOpLowering::matchAndRewrite(
+    cir::PrefetchOp op, OpAdaptor adaptor,
+    mlir::ConversionPatternRewriter &rewriter) const {
+  rewriter.replaceOpWithNewOp<mlir::LLVM::Prefetch>(
+      op, adaptor.getAddr(), adaptor.getIsWrite(), adaptor.getLocality(),
+      /*DataCache*/ 1);
+  return mlir::success();
+}
+
 mlir::LogicalResult CIRToLLVMPtrDiffOpLowering::matchAndRewrite(
     cir::PtrDiffOp op, OpAdaptor adaptor,
     mlir::ConversionPatternRewriter &rewriter) const {
diff --git a/clang/test/CIR/CodeGen/builtin_prefetech.c b/clang/test/CIR/CodeGen/builtin_prefetech.c
new file mode 100644
index 0000000000000..343d9a808ad68
--- /dev/null
+++ b/clang/test/CIR/CodeGen/builtin_prefetech.c
@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-cir %s -o - | FileCheck %s -check-prefix=CIR
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-llvm %s -o - | FileCheck %s -check-prefix=LLVM
+
+void foo(void *a) {
+  __builtin_prefetch(a, 1, 1);
+}
+
+// CIR:  cir.func dso_local @foo(%arg0: !cir.ptr<!void> loc({{.*}}))
+// CIR:    [[PTR_ALLOC:%.*]] = cir.alloca !cir.ptr<!void>, !cir.ptr<!cir.ptr<!void>>, ["a", init] {alignment = 8 : i64}
+// CIR:    cir.store %arg0, [[PTR_ALLOC]] : !cir.ptr<!void>, !cir.ptr<!cir.ptr<!void>>
+// CIR:    [[PTR:%.*]] = cir.load{{.*}} [[PTR_ALLOC]] : !cir.ptr<!cir.ptr<!void>>, !cir.ptr<!void>
+// CIR:    cir.prefetch([[PTR]] : !cir.ptr<!void>) locality(1) write
+// CIR:    cir.return
+
+// LLVM:  define dso_local void @foo(ptr [[ARG0:%.*]])
+// LLVM:    [[PTR_ALLOC:%.*]] = alloca ptr, i64 1
+// LLVM:    store ptr [[ARG0]], ptr [[PTR_ALLOC]]
+// LLVM:    [[PTR:%.*]] = load ptr, ptr [[PTR_ALLOC]]
+// LLVM:    call void @llvm.prefetch.p0(ptr [[PTR]], i32 1, i32 1, i32 1)
+// LLVM:    ret void

``````````

</details>


https://github.com/llvm/llvm-project/pull/164387