[llvm-branch-commits] [flang] release/20.x: [flang] Build fix (#125087) (PR #125213)

[via llvm-branch-commits]

https://github.com/llvmbot updated https://github.com/llvm/llvm-project/pull/125213

>From d5333f265bb7d8a9ba3c51cb7266385827ba7c69 Mon Sep 17 00:00:00 2001
From: vdonaldson <37090318+vdonaldson at users.noreply.github.com>
Date: Thu, 30 Jan 2025 15:15:52 -0500
Subject: [PATCH] [flang] Build fix (#125087)

Reinstate a preprocessor define for a nonstandard exception.

[124978](https://github.com/llvm/llvm-project/issues/124978#event-16113621403)

(cherry picked from commit 7fa1257c35581268deb5f0fc2faa3ae46358f958)
---
 flang/runtime/exceptions.cpp | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/flang/runtime/exceptions.cpp b/flang/runtime/exceptions.cpp
index b41c7cf438f569e..257c71b51edb3d3 100644
--- a/flang/runtime/exceptions.cpp
+++ b/flang/runtime/exceptions.cpp
@@ -13,11 +13,14 @@
 #include <cfenv>
 #if defined(__aarch64__) && !defined(_WIN32)
 #include <fpu_control.h>
-#elif defined(__x86_64__)
+#elif defined(__x86_64__) && !defined(_WIN32)
 #include <xmmintrin.h>
 #endif
 
-// fenv.h may not define exception macros.
+// File fenv.h usually, but not always, defines standard exceptions as both
+// enumerator values and preprocessor #defines. Some x86 environments also
+// define a nonstandard __FE_DENORM enumerator, but without a corresponding
+// #define, which makes it more difficult to determine if it is present or not.
 #ifndef FE_INVALID
 #define FE_INVALID 0
 #endif
@@ -33,6 +36,12 @@
 #ifndef FE_INEXACT
 #define FE_INEXACT 0
 #endif
+#if FE_INVALID == 1 && FE_DIVBYZERO == 4 && FE_OVERFLOW == 8 && \
+    FE_UNDERFLOW == 16 && FE_INEXACT == 32
+#define __FE_DENORM 2
+#else
+#define __FE_DENORM 0
+#endif
 
 namespace Fortran::runtime {
 
@@ -44,11 +53,7 @@ uint32_t RTNAME(MapException)(uint32_t excepts) {
   Terminator terminator{__FILE__, __LINE__};
 
   static constexpr uint32_t v{FE_INVALID};
-#if __x86_64__
-  static constexpr uint32_t s{__FE_DENORM}; // nonstandard, not a #define
-#else
-  static constexpr uint32_t s{0};
-#endif
+  static constexpr uint32_t s{__FE_DENORM};
   static constexpr uint32_t z{FE_DIVBYZERO};
   static constexpr uint32_t o{FE_OVERFLOW};
   static constexpr uint32_t u{FE_UNDERFLOW};