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[CIR][CIRGen][Builtin][X86] Lower __rdtscp #1686

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Merged
merged 1 commit into from
Jun 23, 2025
Merged

[CIR][CIRGen][Builtin][X86] Lower __rdtscp #1686

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19 changes: 18 additions & 1 deletion clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -145,7 +145,24 @@ mlir::Value CIRGenFunction::emitX86BuiltinExpr(unsigned BuiltinID,
.getResult();
}
case X86::BI__builtin_ia32_rdtscp: {
llvm_unreachable("__rdtscp NYI");
// For rdtscp, we need to create a proper struct type to hold {i64, i32}
cir::RecordType resTy = builder.getAnonRecordTy(
{builder.getUInt64Ty(), builder.getUInt32Ty()}, false, false);

auto call = builder
.create<cir::LLVMIntrinsicCallOp>(
getLoc(E->getExprLoc()),
builder.getStringAttr("x86.rdtscp"), resTy)
.getResult();

// Store processor ID in address param
mlir::Value pID = builder.create<cir::ExtractMemberOp>(
getLoc(E->getExprLoc()), builder.getUInt32Ty(), call, 1);
builder.create<cir::StoreOp>(getLoc(E->getExprLoc()), pID, Ops[0]);

// Return the timestamp at index 0
return builder.create<cir::ExtractMemberOp>(getLoc(E->getExprLoc()),
builder.getUInt64Ty(), call, 0);
}
case X86::BI__builtin_ia32_lzcnt_u16:
case X86::BI__builtin_ia32_lzcnt_u32:
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9 changes: 0 additions & 9 deletions clang/test/CIR/CodeGen/X86/builtins-x86.c
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Expand Up @@ -45,12 +45,3 @@ void test_mm_sfence() {
// CIR: {{%.*}} = cir.llvm.intrinsic "x86.sse.sfence" : () -> !void
// LLVM: call void @llvm.x86.sse.sfence()
}

unsigned long long test_rdtsc() {
// CIR-LABEL: @test_rdtsc
// LLVM-LABEL: @test_rdtsc
return __rdtsc();
// CIR: {{%.*}} = cir.llvm.intrinsic "x86.rdtsc" : () -> !u64i
// LLVM: call i64 @llvm.x86.rdtsc
}

35 changes: 35 additions & 0 deletions clang/test/CIR/CodeGen/X86/rd-builtins.c
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@@ -0,0 +1,35 @@
// RUN: %clang_cc1 -ffreestanding -triple x86_64-unknown-linux -Wno-implicit-function-declaration -fclangir -emit-cir -o %t.cir %s
// RUN: FileCheck --check-prefix=CIR --input-file=%t.cir %s
// RUN: %clang_cc1 -ffreestanding -triple x86_64-unknown-linux -Wno-implicit-function-declaration -fclangir -emit-llvm -o %t.ll %s
// RUN: FileCheck --check-prefix=LLVM --input-file=%t.ll %s

// This test mimics clang/test/CodeGen/X86/rd-builtins.c, which eventually
// CIR shall be able to support fully.

#include <x86intrin.h>

unsigned long long test_rdtsc() {
// CIR-LABEL: @test_rdtsc
// LLVM-LABEL: @test_rdtsc
return __rdtsc();
// CIR: {{%.*}} = cir.llvm.intrinsic "x86.rdtsc" : () -> !u64i
// LLVM: call i64 @llvm.x86.rdtsc
}

unsigned long long test_rdtscp(unsigned int *a) {

return __rdtscp(a);

// CIR-LABEL: @__rdtscp
// CIR: [[RDTSCP:%.*]] = cir.llvm.intrinsic "x86.rdtscp" : () -> !rec_anon_struct
// CIR: [[TSC_AUX:%.*]] = cir.extract_member [[RDTSCP]][1] : !rec_anon_struct -> !u32i
// CIR: cir.store [[TSC_AUX]], %{{.*}} : !u32i, !cir.ptr<!u32i>
// CIR: {{%.*}} = cir.extract_member [[RDTSCP]][0] : !rec_anon_struct -> !u64i

// LLVM: @test_rdtscp
// LLVM: [[RDTSCP:%.*]] = call { i64, i32 } @llvm.x86.rdtscp
// LLVM: [[TSC_AUX:%.*]] = extractvalue { i64, i32 } [[RDTSCP]], 1
// LLVM: store i32 [[TSC_AUX]], ptr %{{.*}}
// LLVM: [[TSC:%.*]] = extractvalue { i64, i32 } [[RDTSCP]], 0
}

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