[CIR] Upstream handling for __builtin_prefetch #164387

kimsh02 · 2025-10-21T10:27:03Z

Fix #163886

llvmbot · 2025-10-21T10:27:47Z

@llvm/pr-subscribers-clangir

Author: Shawn K (kimsh02)

Changes

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 --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

llvmbot · 2025-10-21T10:27:47Z

@llvm/pr-subscribers-clang

Author: Shawn K (kimsh02)

Changes

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 --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

Lancern

Thanks for authoring this, some comments inline.

clang/include/clang/CIR/Dialect/IR/CIROps.td

clang/test/CIR/CodeGen/builtin_prefetech.c

clang/include/clang/CIR/Dialect/IR/CIROps.td

clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp

clang/include/clang/CIR/Dialect/IR/CIROps.td

clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp

clang/test/CIR/CodeGen/builtin_prefetech.c

clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp

clang/include/clang/CIR/Dialect/IR/CIROps.td

kimsh02 · 2025-10-22T01:19:36Z

I'm still new to upstreaming, so thanks for your patience and all the feedback

kimsh02 · 2025-10-22T04:27:53Z

Getting this failed test case, not sure if I broke something.

Command Output (stdout):
--
# RUN: at line 1
/Users/kimsh/Downloads/forked/llvm-project/build-clang-cir/bin/clang -cc1 -internal-isystem /Users/kimsh/Downloads/forked/llvm-project/build-clang-cir/lib/clang/22/include -nostdsysteminc -triple aarch64-unknown-linux-gnu -fclangir -emit-cir -fdump-record-layouts /Users/kimsh/Downloads/forked/llvm-project/clang/test/CIR/CodeGen/aapcs-volatile-bitfields.c -o /Users/kimsh/Downloads/forked/llvm-project/build-clang-cir/tools/clang/test/CIR/CodeGen/Output/aapcs-volatile-bitfields.c.tmp.cir 1> /Users/kimsh/Downloads/forked/llvm-project/build-clang-cir/tools/clang/test/CIR/CodeGen/Output/aapcs-volatile-bitfields.c.tmp.cirlayout
# executed command: /Users/kimsh/Downloads/forked/llvm-project/build-clang-cir/bin/clang -cc1 -internal-isystem /Users/kimsh/Downloads/forked/llvm-project/build-clang-cir/lib/clang/22/include -nostdsysteminc -triple aarch64-unknown-linux-gnu -fclangir -emit-cir -fdump-record-layouts /Users/kimsh/Downloads/forked/llvm-project/clang/test/CIR/CodeGen/aapcs-volatile-bitfields.c -o /Users/kimsh/Downloads/forked/llvm-project/build-clang-cir/tools/clang/test/CIR/CodeGen/Output/aapcs-volatile-bitfields.c.tmp.cir
# .---command stderr------------
# | Unsupported redirect: (('>', 1), '/Users/kimsh/Downloads/forked/llvm-project/build-clang-cir/tools/clang/test/CIR/CodeGen/Output/aapcs-volatile-bitfields.c.tmp.cirlayout')
# `-----------------------------
# error: command failed with exit status: 127

--

********************
********************
Failed Tests (1):
  Clang :: CIR/CodeGen/aapcs-volatile-bitfields.c

andykaylor · 2025-10-22T16:47:50Z

I'm still new to upstreaming, so thanks for your patience and all the feedback

That's totally expected. I appreciate your willingness to help.

BTW, the CI failure was unrelated to your change and is fixed now.

kimsh02 · 2025-10-22T21:11:49Z

@andykaylor I merged again and looking at the build artifact for the build/test on Linux, and I think the failure is unrelated to my PR again?

andykaylor · 2025-10-22T22:00:30Z

@andykaylor I merged again and looking at the build artifact for the build/test on Linux, and I think the failure is unrelated to my PR again?

Yes. This one is because of an MLIR function that has been deprecated. That's fixed by this commit: #164656

I guess the CI runs using the commit that your PR is based on rather than trying to merge your PR onto the top of trunk. I'm rebasing a couple of other commits for this same reason. Normally I wouldn't worry about unrelated failures, but this one stops the build so none of the usual CI testing was done in this case.

andykaylor · 2025-10-22T22:03:09Z

@andykaylor I merged again and looking at the build artifact for the build/test on Linux, and I think the failure is unrelated to my PR again?

Yes. This one is because of an MLIR function that has been deprecated. That's fixed by this commit: #164656

I guess the CI runs using the commit that your PR is based on rather than trying to merge your PR onto the top of trunk. I'm rebasing a couple of other commits for this same reason. Normally I wouldn't worry about unrelated failures, but this one stops the build so none of the usual CI testing was done in this case.

Actually, it looks like we missed some. I'll put up another PR to fix it.

andykaylor · 2025-10-22T22:13:44Z

#164719 should fix the CI issues. And I think I was wrong about CI not merging with top of trunk. The problem was just that we still had deprecated calls in top of trunk.

andykaylor

lgtm

Lancern

LGTM

kimsh02 requested review from andykaylor, bcardosolopes, lanza and xlauko as code owners October 21, 2025 10:27

llvmbot added clang Clang issues not falling into any other category ClangIR Anything related to the ClangIR project labels Oct 21, 2025

[CIR] Upstream handling for __builtin_prefetch

0b07a4a

Lancern requested changes Oct 21, 2025

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andykaylor reviewed Oct 21, 2025

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645ffaa

kimsh02 force-pushed the cir-builtin-prefetch branch from 760e039 to 645ffaa Compare October 22, 2025 01:45

kimsh02 requested a review from andykaylor October 22, 2025 01:46

Merge branch 'main' into cir-builtin-prefetch

778dee7

Merge branch 'main' into cir-builtin-prefetch

5f40d22

andykaylor approved these changes Oct 22, 2025

View reviewed changes

Merge branch 'main' into cir-builtin-prefetch

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kimsh02 requested a review from andykaylor October 23, 2025 02:30

Lancern approved these changes Oct 23, 2025

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Lancern merged commit 3107c2f into llvm:main Oct 23, 2025
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[CIR] Upstream handling for __builtin_prefetch #164387

[CIR] Upstream handling for __builtin_prefetch #164387

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kimsh02 commented Oct 21, 2025

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kimsh02 commented Oct 22, 2025 •

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