Revert long double checks (#3133)

* Revert "Remove long double conversion work-arounds (#3097)"

This reverts commit 1e1dac1dac58fa18f6b7788346d1ba7d3315b0f9.

* Update comments to reflect newer systems

1 files changed, 93 insertions, 0 deletions

diff --git a/config/cmake/ConfigureChecks.cmake b/config/cmake/ConfigureChecks.cmake
index 32faed4..8c401d9 100644
--- a/config/cmake/ConfigureChecks.cmake
+++ b/config/cmake/ConfigureChecks.cmake
@@ -560,6 +560,19 @@ endif ()
 MARK_AS_ADVANCED (HDF5_STRICT_FORMAT_CHECKS)
 
 # ----------------------------------------------------------------------
+# Decide whether the data accuracy has higher priority during data
+# conversions.  If not, some hard conversions will still be preferred even
+# though the data may be wrong (for example, some compilers don't
+# support denormalized floating values) to maximize speed.
+#-----------------------------------------------------------------------------
+option (HDF5_WANT_DATA_ACCURACY "IF data accuracy is guaranteed during data conversions" ON)
+mark_as_advanced (HDF5_WANT_DATA_ACCURACY)
+if (HDF5_WANT_DATA_ACCURACY)
+  set (${HDF_PREFIX}_WANT_DATA_ACCURACY 1)
+endif ()
+MARK_AS_ADVANCED (HDF5_WANT_DATA_ACCURACY)
+
+# ----------------------------------------------------------------------
 # Decide whether the presence of user's exception handling functions is
 # checked and data conversion exceptions are returned.  This is mainly
 # for the speed optimization of hard conversions.  Soft conversions can
@@ -847,3 +860,83 @@ if (HDF5_BUILD_FORTRAN)
   message (STATUS "maximum decimal precision for C var - ${${HDF_PREFIX}_PAC_C_MAX_REAL_PRECISION}")
 
 endif()
+
+#-----------------------------------------------------------------------------
+# Macro to determine the various conversion capabilities
+#-----------------------------------------------------------------------------
+macro (H5ConversionTests TEST msg)
+  if (NOT DEFINED ${TEST})
+    TRY_RUN (${TEST}_RUN   ${TEST}_COMPILE
+        ${CMAKE_BINARY_DIR}
+        ${HDF_RESOURCES_DIR}/ConversionTests.c
+        CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=-D${TEST}_TEST
+        OUTPUT_VARIABLE OUTPUT
+    )
+    if (${TEST}_COMPILE)
+      if (${TEST}_RUN EQUAL "0")
+        set (${TEST} 1 CACHE INTERNAL ${msg})
+        message (VERBOSE "${msg}... yes")
+      else ()
+        set (${TEST} "" CACHE INTERNAL ${msg})
+        message (VERBOSE "${msg}... no")
+        file (APPEND ${CMAKE_BINARY_DIR}/CMakeFiles/CMakeError.log
+              "Test ${TEST} Run failed with the following output and exit code:\n ${OUTPUT}\n"
+        )
+      endif ()
+    else ()
+      set (${TEST} "" CACHE INTERNAL ${msg})
+      message (VERBOSE "${msg}... no")
+      file (APPEND ${CMAKE_BINARY_DIR}/CMakeFiles/CMakeError.log
+          "Test ${TEST} Compile failed with the following output:\n ${OUTPUT}\n"
+      )
+    endif ()
+
+  endif ()
+endmacro ()
+
+#-----------------------------------------------------------------------------
+# Check various conversion capabilities
+#-----------------------------------------------------------------------------
+
+# ----------------------------------------------------------------------
+# Set the flag to indicate that the machine is using a special algorithm toconvert
+# 'long double' to '(unsigned) long' values.  (This flag should only be set for
+# the IBM Power Linux.  When the bit sequence of long double is
+# 0x4351ccf385ebc8a0bfcc2a3c3d855620, the converted value of (unsigned)long
+# is 0x004733ce17af227f, not the same as the library's conversion to 0x004733ce17af2282.
+# The machine's conversion gets the correct value.  We define the macro and disable
+# this kind of test until we figure out what algorithm they use.
+#-----------------------------------------------------------------------------
+H5ConversionTests (${HDF_PREFIX}_LDOUBLE_TO_LONG_SPECIAL  "Checking IF your system converts long double to (unsigned) long values with special algorithm")
+# ----------------------------------------------------------------------
+# Set the flag to indicate that the machine is using a special algorithm
+# to convert some values of '(unsigned) long' to 'long double' values.
+# (This flag should be off for all machines, except for IBM Power Linux,
+# when the bit sequences are 003fff..., 007fff..., 00ffff..., 01ffff...,
+# ..., 7fffff..., the compiler uses a unknown algorithm.  We define a
+# macro and skip the test for now until we know about the algorithm.
+#-----------------------------------------------------------------------------
+H5ConversionTests (${HDF_PREFIX}_LONG_TO_LDOUBLE_SPECIAL "Checking IF your system can convert (unsigned) long to long double values with special algorithm")
+# ----------------------------------------------------------------------
+# Set the flag to indicate that the machine can accurately convert
+# 'long double' to '(unsigned) long long' values.  (This flag should be set for
+# all machines, except for Mac OS 10.4 and SGI IRIX64 6.5.  When the bit sequence
+# of long double is 0x4351ccf385ebc8a0bfcc2a3c..., the values of (unsigned)long long
+# start to go wrong on these two machines.  Adjusting it higher to
+# 0x4351ccf385ebc8a0dfcc... or 0x4351ccf385ebc8a0ffcc... will make the converted
+# values wildly wrong.  This test detects this wrong behavior and disable the test.
+#-----------------------------------------------------------------------------
+H5ConversionTests (${HDF_PREFIX}_LDOUBLE_TO_LLONG_ACCURATE "Checking IF correctly converting long double to (unsigned) long long values")
+# ----------------------------------------------------------------------
+# Set the flag to indicate that the machine can accurately convert
+# '(unsigned) long long' to 'long double' values.  (This flag should be set for
+# all machines, except for Mac OS 10.4, when the bit sequences are 003fff...,
+# 007fff..., 00ffff..., 01ffff..., ..., 7fffff..., the converted values are twice
+# as big as they should be.
+#-----------------------------------------------------------------------------
+H5ConversionTests (${HDF_PREFIX}_LLONG_TO_LDOUBLE_CORRECT "Checking IF correctly converting (unsigned) long long to long double values")
+# ----------------------------------------------------------------------
+# Set the flag to indicate that the machine can accurately convert
+# some long double values
+#-----------------------------------------------------------------------------
+H5ConversionTests (${HDF_PREFIX}_DISABLE_SOME_LDOUBLE_CONV "Checking IF the cpu is power9 and cannot correctly converting long double values")