[llvm] [Exegesis] CPU selection, when native arch and target mismatch (PR #131014)

[via llvm-commits]

https://github.com/AnastasiyaChernikova updated https://github.com/llvm/llvm-project/pull/131014

>From 3d311f4cd32e7fe016b3f83ef780d25ca589e172 Mon Sep 17 00:00:00 2001
From: Anastasiya Chernikova <anastasiya.chernikova at syntacore.com>
Date: Wed, 19 Mar 2025 16:17:36 +0300
Subject: [PATCH] [Exegesis] Output error if mcpu flag is missing or incorrect
 when cross compiling

---
 .../X86/mcpu_not_set_during_cross_compilation.s       |  3 +++
 llvm/tools/llvm-exegesis/lib/LlvmState.cpp            | 11 ++++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/tools/llvm-exegesis/X86/mcpu_not_set_during_cross_compilation.s

diff --git a/llvm/test/tools/llvm-exegesis/X86/mcpu_not_set_during_cross_compilation.s b/llvm/test/tools/llvm-exegesis/X86/mcpu_not_set_during_cross_compilation.s
new file mode 100644
index 0000000000000..f2a4e51552eb1
--- /dev/null
+++ b/llvm/test/tools/llvm-exegesis/X86/mcpu_not_set_during_cross_compilation.s
@@ -0,0 +1,3 @@
+# RUN: not llvm-exegesis -mtriple=riscv64-unknown-linux-gnu -mode=latency --benchmark-phase=assemble-measured-code -opcode-name=ADD 2>&1 | FileCheck %s
+
+# CHECK: llvm-exegesis error: A CPU must be explicitly specified when cross compiling. To see all possible options for riscv64-unknown-linux-gnu triple use -mcpu=help
diff --git a/llvm/tools/llvm-exegesis/lib/LlvmState.cpp b/llvm/tools/llvm-exegesis/lib/LlvmState.cpp
index 9502cae993f67..88c0d67694afb 100644
--- a/llvm/tools/llvm-exegesis/lib/LlvmState.cpp
+++ b/llvm/tools/llvm-exegesis/lib/LlvmState.cpp
@@ -42,8 +42,17 @@ Expected<LLVMState> LLVMState::Create(std::string TripleName,
   // Update Triple with the updated triple from the target lookup.
   TripleName = TheTriple.str();
 
-  if (CpuName == "native")
+  if (CpuName == "native") {
+    // case for cross generating, when native arch and target mismatch
+    if ((Triple(sys::getProcessTriple()).getArch() !=
+         Triple(TripleName).getArch()))
+      return make_error<StringError>(
+          "A CPU must be explicitly specified when cross compiling. To see all "
+          "possible options for " +
+              TripleName + " triple use -mcpu=help",
+          inconvertibleErrorCode());
     CpuName = std::string(sys::getHostCPUName());
+  }
 
   std::unique_ptr<MCSubtargetInfo> STI(
       TheTarget->createMCSubtargetInfo(TripleName, CpuName, ""));