[flang] [llvm] [flang-rt][device] Enable MapException on the device with error message (PR #171705)

[Valentin Clement バレンタイン クレメン via llvm-commits]

https://github.com/clementval created https://github.com/llvm/llvm-project/pull/171705

As it is done in `flang-rt/lib/runtime/edit-input.cpp`, emit a runtime error message when trying to raise IEEE expiation on the device. `MapException` and `feraiseexcept` are used in the lowering of the nearest intrinsic even on the device. 

>From d94ed440892fdbfecf161060ae46053009c07f67 Mon Sep 17 00:00:00 2001
From: Valentin Clement <clementval at gmail.com>
Date: Wed, 10 Dec 2025 13:11:04 -0800
Subject: [PATCH] [flang-rt][device] Enable MapException on the device with
 error message

---
 flang-rt/lib/runtime/CMakeLists.txt      |  1 +
 flang-rt/lib/runtime/exceptions.cpp      | 12 ++++++++++--
 flang/include/flang/Runtime/exceptions.h |  4 ++--
 3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/flang-rt/lib/runtime/CMakeLists.txt b/flang-rt/lib/runtime/CMakeLists.txt
index 4be679d1ca8ac..0cea6c2d52652 100644
--- a/flang-rt/lib/runtime/CMakeLists.txt
+++ b/flang-rt/lib/runtime/CMakeLists.txt
@@ -57,6 +57,7 @@ set(supported_sources
   edit-input.cpp
   edit-output.cpp
   environment.cpp
+  exceptions.cpp
   external-unit.cpp
   extrema.cpp
   file.cpp
diff --git a/flang-rt/lib/runtime/exceptions.cpp b/flang-rt/lib/runtime/exceptions.cpp
index e5ba06c92ca90..fc5021fdb9036 100644
--- a/flang-rt/lib/runtime/exceptions.cpp
+++ b/flang-rt/lib/runtime/exceptions.cpp
@@ -49,9 +49,14 @@ extern "C" {
 
 // Map a set of Fortran ieee_arithmetic module exceptions to a libm fenv.h
 // excepts value.
-uint32_t RTNAME(MapException)(uint32_t excepts) {
+uint32_t RTDEF(MapException)(uint32_t excepts) {
   Terminator terminator{__FILE__, __LINE__};
 
+#if defined(RT_DEVICE_COMPILATION)
+  terminator.Crash(
+      "not implemented yet: raising IEEE FP exception in device code: %d",
+      excepts);
+#else
   static constexpr uint32_t v{FE_INVALID};
   static constexpr uint32_t s{__FE_DENORM};
   static constexpr uint32_t z{FE_DIVBYZERO};
@@ -74,6 +79,7 @@ uint32_t RTNAME(MapException)(uint32_t excepts) {
   }
   uint32_t except_value = map[excepts];
   return except_value;
+#endif
 }
 
 // The following exception processing routines have a libm call component,
@@ -87,11 +93,13 @@ void RTNAME(feclearexcept)(uint32_t excepts) {
   _mm_setcsr(_mm_getcsr() & ~(excepts & _MM_EXCEPT_MASK));
 #endif
 }
-void RTNAME(feraiseexcept)(uint32_t excepts) {
+void RTDEF(feraiseexcept)(uint32_t excepts) {
+#if !defined(RT_DEVICE_COMPILATION)
   feraiseexcept(excepts);
 #if defined(_MM_EXCEPT_DENORM)
   _mm_setcsr(_mm_getcsr() | (excepts & _MM_EXCEPT_MASK));
 #endif
+#endif
 }
 uint32_t RTNAME(fetestexcept)(uint32_t excepts) {
 #if defined(_MM_EXCEPT_DENORM)
diff --git a/flang/include/flang/Runtime/exceptions.h b/flang/include/flang/Runtime/exceptions.h
index c76376e36ed6d..2497a48402233 100644
--- a/flang/include/flang/Runtime/exceptions.h
+++ b/flang/include/flang/Runtime/exceptions.h
@@ -24,12 +24,12 @@ extern "C" {
 
 // Map a set of IEEE_FLAG_TYPE exception values to a libm fenv.h excepts value.
 // This mapping is done at runtime to support cross compilation.
-std::uint32_t RTNAME(MapException)(std::uint32_t excepts);
+std::uint32_t RTDECL(MapException)(std::uint32_t excepts);
 
 // Exception processing functions that call the corresponding libm functions,
 // and also include support for denormal exceptions where available.
 void RTNAME(feclearexcept)(std::uint32_t excepts);
-void RTNAME(feraiseexcept)(std::uint32_t excepts);
+void RTDECL(feraiseexcept)(std::uint32_t excepts);
 std::uint32_t RTNAME(fetestexcept)(std::uint32_t excepts);
 void RTNAME(fedisableexcept)(std::uint32_t excepts);
 void RTNAME(feenableexcept)(std::uint32_t excepts);