[clang] [CIR][X86] Add support for `cpuid`/`cpuidex` (PR #173197)
Roberto Turrado Camblor via cfe-commits
cfe-commits at lists.llvm.org
Sun Dec 21 13:20:09 PST 2025
https://github.com/rturrado updated https://github.com/llvm/llvm-project/pull/173197
>From 412f88f726643427c3be6137028d4938878d3ef3 Mon Sep 17 00:00:00 2001
From: rturrado <rturrado at gmail.com>
Date: Fri, 19 Dec 2025 21:02:27 +0100
Subject: [PATCH] [CIR][X86] Add support for cpuid/cpuidex
---
clang/include/clang/CIR/Dialect/IR/CIROps.td | 27 +++++++
clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp | 12 +++-
.../CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp | 70 +++++++++++++++++++
3 files changed, 108 insertions(+), 1 deletion(-)
diff --git a/clang/include/clang/CIR/Dialect/IR/CIROps.td b/clang/include/clang/CIR/Dialect/IR/CIROps.td
index 7e7424fd71878..7d05fce0fdf09 100644
--- a/clang/include/clang/CIR/Dialect/IR/CIROps.td
+++ b/clang/include/clang/CIR/Dialect/IR/CIROps.td
@@ -5762,4 +5762,31 @@ def CIR_BlockAddressOp : CIR_Op<"block_address", [Pure]> {
}];
}
+//===----------------------------------------------------------------------===//
+// CpuIdOp
+//===----------------------------------------------------------------------===//
+
+def CIR_CpuIdOp : CIR_Op<"cpuid"> {
+ let summary = "Get information about the CPU";
+ let description = [{
+ The `cir.cpuid` operation takes a base pointer to an array of 4 integers, a
+ function ID and a sub-function ID. The array of 4 integers is filled with
+ different information about the processor.
+
+ Example:
+
+ ```mlir
+ cir.cpuid %basePtr, %funcId, %subFuncId
+ : (!cir.ptr<!cir.array<4 x !s32i>>, !s32i, !s32i)
+ ```
+ }];
+
+ let arguments =
+ (ins Arg<CIR_PtrToArray, "array address", [MemWrite]>:$basePtr,
+ CIR_SInt32:$funcId, CIR_SInt32:$subFuncId);
+ // TODO: remove once we can return an optional mlir::Value from
+ // emitX86BuiltinExpr
+ let results = (outs CIR_VectorType:$result);
+}
+
#endif // CLANG_CIR_DIALECT_IR_CIROPS_TD
diff --git a/clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp b/clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp
index 1c87e945de846..bf9810eff498d 100644
--- a/clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp
@@ -25,6 +25,7 @@
#include "clang/CIR/Dialect/IR/CIRTypes.h"
#include "clang/CIR/MissingFeatures.h"
#include "llvm/ADT/Sequence.h"
+#include "llvm/IR/InlineAsm.h"
#include "llvm/Support/ErrorHandling.h"
#include <string>
@@ -1835,7 +1836,16 @@ CIRGenFunction::emitX86BuiltinExpr(unsigned builtinID, const CallExpr *expr) {
case X86::BI__builtin_ia32_cvtneps2bf16_256_mask:
case X86::BI__builtin_ia32_cvtneps2bf16_512_mask:
case X86::BI__cpuid:
- case X86::BI__cpuidex:
+ case X86::BI__cpuidex: {
+ mlir::Location loc = getLoc(expr->getExprLoc());
+ mlir::Type i32Ty = builder.getSInt32Ty();
+ mlir::Value subFuncId = builtinID == X86::BI__cpuidex
+ ? ops[2]
+ : builder.getConstInt(loc, sInt32Ty, 0);
+ cir::CpuIdOp::create(builder, loc, i32Ty, /*basePtr=*/ops[0],
+ /*funcId=*/ops[1], /*subFuncId=*/subFuncId);
+ return mlir::Value{};
+ }
case X86::BI__emul:
case X86::BI__emulu:
case X86::BI__mulh:
diff --git a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
index eb0a219f18618..24924085ea9ea 100644
--- a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
+++ b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
@@ -4193,6 +4193,76 @@ mlir::LogicalResult CIRToLLVMAwaitOpLowering::matchAndRewrite(
return mlir::failure();
}
+mlir::LogicalResult CIRToLLVMCpuIdOpLowering::matchAndRewrite(
+ cir::CpuIdOp op, OpAdaptor adaptor,
+ mlir::ConversionPatternRewriter &rewriter) const {
+ mlir::Type i32Ty = rewriter.getI32Type();
+ mlir::Type i64Ty = rewriter.getI64Type();
+ mlir::Type i32PtrTy = mlir::LLVM::LLVMPointerType::get(i32Ty.getContext(), 0);
+
+ mlir::Type cpuidRetTy = mlir::LLVM::LLVMStructType::getLiteral(
+ rewriter.getContext(), {i32Ty, i32Ty, i32Ty, i32Ty});
+
+ mlir::Value funcId = adaptor.getFuncId();
+ mlir::Value subFuncId = adaptor.getSubFuncId();
+ mlir::StringAttr opNameAttr = op->getAttrOfType<mlir::StringAttr>("name");
+ if (!opNameAttr)
+ return mlir::failure();
+ if (opNameAttr.getValue() == "cpuid")
+ subFuncId = mlir::LLVM::ConstantOp::create(rewriter, op.getLoc(), i32Ty, 0);
+ std::vector operands{funcId, subFuncId};
+
+ StringRef asmString, constraints;
+ mlir::ModuleOp moduleOp = op->getParentOfType<mlir::ModuleOp>();
+ mlir::StringAttr tripleAttr =
+ moduleOp->getAttrOfType<mlir::StringAttr>("llvm.target_triple");
+ if (!tripleAttr)
+ return mlir::failure();
+ llvm::Triple triple(tripleAttr.getValue().str());
+ if (triple.getArch() == llvm::Triple::x86) {
+ asmString = "cpuid";
+ constraints = "={ax},={bx},={cx},={dx},{ax},{cx}";
+ } else {
+ // x86-64 uses %rbx as the base register, so preserve it.
+ asmString = "xchgq %rbx, ${1:q}\n"
+ "cpuid\n"
+ "xchgq %rbx, ${1:q}";
+ constraints = "={ax},=r,={cx},={dx},0,2";
+ }
+
+ mlir::Value inlineAsm =
+ mlir::LLVM::InlineAsmOp::create(
+ rewriter, op.getLoc(), cpuidRetTy, mlir::ValueRange(operands),
+ rewriter.getStringAttr(asmString),
+ rewriter.getStringAttr(constraints),
+ /*has_side_effects=*/mlir::UnitAttr{},
+ /*is_align_stack=*/mlir::UnitAttr{},
+ /*tail_call_kind=*/mlir::LLVM::TailCallKindAttr{},
+ /*asm_dialect=*/mlir::LLVM::AsmDialectAttr{},
+ /*operand_attrs=*/mlir::ArrayAttr{})
+ .getResult(0);
+
+ mlir::Value basePtr = adaptor.getBasePtr();
+
+ mlir::DataLayout layout(op->getParentOfType<mlir::ModuleOp>());
+ unsigned alignment = layout.getTypeABIAlignment(i32Ty);
+ for (unsigned i = 0; i < 4; i++) {
+ mlir::Value extracted =
+ mlir::LLVM::ExtractValueOp::create(rewriter, op.getLoc(), inlineAsm, i)
+ .getResult();
+ mlir::Value index = mlir::LLVM::ConstantOp::create(
+ rewriter, op.getLoc(), i64Ty, rewriter.getI64IntegerAttr(i));
+ llvm::SmallVector<mlir::Value, 1> gepIndices = {index};
+ mlir::Value storePtr = mlir::LLVM::GEPOp::create(
+ rewriter, op.getLoc(), i32PtrTy, i32Ty, basePtr,
+ gepIndices, mlir::LLVM::GEPNoWrapFlags::none)
+ .getResult();
+ mlir::LLVM::StoreOp::create(rewriter, op.getLoc(), extracted, storePtr,
+ alignment);
+ }
+ return mlir::success();
+}
+
std::unique_ptr<mlir::Pass> createConvertCIRToLLVMPass() {
return std::make_unique<ConvertCIRToLLVMPass>();
}
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