[clang] [MSVC, ARM64] Add __prefetch intrinsic (PR #67174)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-codegen

<details>
<summary>Changes</summary>

Implement __prefetch intrinsic. 

MSVC docs: https://learn.microsoft.com/en-us/cpp/intrinsics/arm64-intrinsics?view=msvc-170

Bug: https://github.com/llvm/llvm-project/issues/65405

---
Full diff: https://github.com/llvm/llvm-project/pull/67174.diff


4 Files Affected:

- (modified) clang/include/clang/Basic/BuiltinsAArch64.def (+2) 
- (modified) clang/lib/CodeGen/CGBuiltin.cpp (+9) 
- (modified) clang/lib/Headers/intrin.h (+2) 
- (modified) clang/test/CodeGen/arm64-microsoft-intrinsics.c (+10) 


``````````diff
diff --git a/clang/include/clang/Basic/BuiltinsAArch64.def b/clang/include/clang/Basic/BuiltinsAArch64.def
index 12c7a371e0fbdb9..82a1ba3c82ad358 100644
--- a/clang/include/clang/Basic/BuiltinsAArch64.def
+++ b/clang/include/clang/Basic/BuiltinsAArch64.def
@@ -283,6 +283,8 @@ TARGET_HEADER_BUILTIN(_CountLeadingZeros64, "UiULLi", "nh", INTRIN_H, ALL_MS_LAN
 TARGET_HEADER_BUILTIN(_CountOneBits, "UiUNi", "nh", INTRIN_H, ALL_MS_LANGUAGES, "")
 TARGET_HEADER_BUILTIN(_CountOneBits64, "UiULLi", "nh", INTRIN_H, ALL_MS_LANGUAGES, "")
 
+TARGET_HEADER_BUILTIN(__prefetch, "vv*", "nh", INTRIN_H, ALL_MS_LANGUAGES, "")
+
 #undef BUILTIN
 #undef LANGBUILTIN
 #undef TARGET_BUILTIN
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 4a73403cb3b9a72..6944ff8f6ca745e 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -10834,6 +10834,15 @@ Value *CodeGenFunction::EmitAArch64BuiltinExpr(unsigned BuiltinID,
     return Result;
   }
 
+  if (BuiltinID == AArch64::BI__prefetch) {
+    Value *Address = EmitScalarExpr(E->getArg(0));
+    Value *RW = llvm::ConstantInt::get(Int32Ty, 0);
+    Value *Locality = ConstantInt::get(Int32Ty, 3);
+    Value *Data = llvm::ConstantInt::get(Int32Ty, 1);
+    Function *F = CGM.getIntrinsic(Intrinsic::prefetch, Address->getType());
+    return Builder.CreateCall(F, {Address, RW, Locality, Data});
+  }
+
   // Handle MSVC intrinsics before argument evaluation to prevent double
   // evaluation.
   if (std::optional<MSVCIntrin> MsvcIntId =
diff --git a/clang/lib/Headers/intrin.h b/clang/lib/Headers/intrin.h
index 4678c527bfaab5a..9ebaea9fee94214 100644
--- a/clang/lib/Headers/intrin.h
+++ b/clang/lib/Headers/intrin.h
@@ -586,6 +586,8 @@ unsigned int _CountLeadingZeros(unsigned long);
 unsigned int _CountLeadingZeros64(unsigned _int64);
 unsigned int _CountOneBits(unsigned long);
 unsigned int _CountOneBits64(unsigned __int64);
+
+void __cdecl __prefetch(void *);
 #endif
 
 /*----------------------------------------------------------------------------*\
diff --git a/clang/test/CodeGen/arm64-microsoft-intrinsics.c b/clang/test/CodeGen/arm64-microsoft-intrinsics.c
index b15defb0894e92e..44b2ee28fe56814 100644
--- a/clang/test/CodeGen/arm64-microsoft-intrinsics.c
+++ b/clang/test/CodeGen/arm64-microsoft-intrinsics.c
@@ -402,6 +402,16 @@ unsigned int check_CountOneBits64(unsigned __int64 arg1) {
 // CHECK-MSCOMPAT: ret i32 %[[VAR2]]
 // CHECK-LINUX: error: call to undeclared function '_CountOneBits64'
 
+void check__prefetch(void *arg1) {
+  return __prefetch(arg1);
+}
+
+// CHECK-MSCOMPAT: %[[ARG1:.*]].addr = alloca ptr, align 8
+// CHECK-MSCOMPAT: store ptr %[[ARG1]], ptr %[[ARG1]].addr, align 8
+// CHECK-MSCOMPAT: %[[VAR0:.*]] = load ptr, ptr %[[ARG1]].addr, align 8
+// CHECK-MSCOMPAT: call void @llvm.prefetch.p0(ptr %[[VAR0]], i32 0, i32 3, i32 1)
+// CHECK-MSCOMPAT: ret void
+
 
 // CHECK-MSCOMPAT: ![[MD2]] = !{!"x18"}
 // CHECK-MSCOMPAT: ![[MD3]] = !{!"sp"}

``````````

</details>


https://github.com/llvm/llvm-project/pull/67174