From b93ee30ab53b7b73f79ddf21626777219efa4664 Mon Sep 17 00:00:00 2001
From: Kenneth Moreland <morelandkd@ornl.gov>
Date: Wed, 24 Apr 2024 13:29:26 -0400
Subject: [PATCH] Enable non-finite values with Intel compiler

The Intel compiler by default turns on an optimization that assumes that
all floating point values are finite. This breaks any ligitimate uses of
non-finite values including checking values with functions like `isnan`
and `isinf`. Turn off this feature for the intel compiler.
---
 CMake/VTKmCompilerFlags.cmake   | 13 +++++++++++++
 docs/changelog/intel-finites.md |  6 ++++++
 2 files changed, 19 insertions(+)
 create mode 100644 docs/changelog/intel-finites.md

diff --git a/CMake/VTKmCompilerFlags.cmake b/CMake/VTKmCompilerFlags.cmake
index 2a7f4841f..b9be52053 100644
--- a/CMake/VTKmCompilerFlags.cmake
+++ b/CMake/VTKmCompilerFlags.cmake
@@ -90,6 +90,19 @@ set_target_properties(
   EXPORT_NAME developer_flags
   )
 
+# Intel OneAPI compilers >= 2021.2.0 turn on "fast math" at any non-zero
+# optimization level. Suppress this non-standard behavior using the
+# `-fp-model=precise` flag.
+set(intel_oneapi_compiler_version_min "2021.2.0")
+set(is_lang "$<COMPILE_LANGUAGE:CXX>")
+set(is_intelllvm "$<CXX_COMPILER_ID:IntelLLVM>")
+set(is_intelllvm_fastmath_assuming_version "$<VERSION_GREATER_EQUAL:$<CXX_COMPILER_VERSION>,${intel_oneapi_compiler_version_min}>")
+set(intel_oneapi_compiler_detections
+  "$<AND:${is_lang},${is_intelllvm},${is_intelllvm_fastmath_assuming_version}>")
+target_compile_options(vtkm_developer_flags
+  INTERFACE
+    "$<BUILD_INTERFACE:$<${intel_oneapi_compiler_detections}:-fp-model=precise>>")
+
 # Additional warnings just for Clang 3.5+, and AppleClang 7+
 # about failures to vectorize.
 if (VTKM_COMPILER_IS_CLANG AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 3.4)
diff --git a/docs/changelog/intel-finites.md b/docs/changelog/intel-finites.md
new file mode 100644
index 000000000..0b2128839
--- /dev/null
+++ b/docs/changelog/intel-finites.md
@@ -0,0 +1,6 @@
+# Enable non-finite values with Intel compiler
+
+The Intel compiler by default turns on an optimization that assumes that
+all floating point values are finite. This breaks any ligitimate uses of
+non-finite values including checking values with functions like `isnan`
+and `isinf`. Turn off this feature for the intel compiler.