leonardchan created this revision.
leonardchan added reviewers: phosek, mcgrathr, jakehehrlich.
leonardchan added a project: clang.
Herald added a subscriber: mgorny.
This patch includes checks that the precision macros used for the fixed point
fractional and integral bits meet the requirements for clause 6.2.6.3 in
http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1169.pdf.
Checks for any disagreements with the recommendations will throw warnings.
I also added my own warning that recommends the integral and fractional bits
for _Accum types take up the width of the whole underlying integer to prevent
having to mask out the padding bits when performing comparisons.
Repository:
rC Clang
https://reviews.llvm.org/D47030
Files:
cmake/modules/InitFixedPointBits.cmake
Index: cmake/modules/InitFixedPointBits.cmake
===
--- cmake/modules/InitFixedPointBits.cmake
+++ cmake/modules/InitFixedPointBits.cmake
@@ -60,26 +60,170 @@
set(ULACCUM_IBIT 32)
endif()
-# Checks for each bit size
+# Checks for each bit size defined in clause 6.2.6.3
+
+# Cannot go below the minimum number of fractional and integral bits for the
+# various types specified in clause 7.18a.3.
+function(assert_min_bits macro min_bits)
+ set("macro_name" ${macro})
+ set("macro_val" ${${macro}})
+ if(${macro_val} LESS ${min_bits})
+message(FATAL_ERROR "The minimum value allowed for ${macro_name} is ${min_bits}. "
+ "${macro_val} was provided.")
+ endif()
+endfunction()
+
+assert_min_bits(SFRACT_FBIT 7)
+assert_min_bits(FRACT_FBIT 15)
+assert_min_bits(LFRACT_FBIT 23)
+assert_min_bits(USFRACT_FBIT 7)
+assert_min_bits(UFRACT_FBIT 15)
+assert_min_bits(ULFRACT_FBIT 23)
+
+assert_min_bits(SACCUM_FBIT 7)
+assert_min_bits(ACCUM_FBIT 15)
+assert_min_bits(LACCUM_FBIT 23)
+assert_min_bits(USACCUM_FBIT 7)
+assert_min_bits(UACCUM_FBIT 15)
+assert_min_bits(ULACCUM_FBIT 23)
+
+assert_min_bits(SACCUM_IBIT 4)
+assert_min_bits(ACCUM_IBIT 4)
+assert_min_bits(LACCUM_IBIT 4)
+assert_min_bits(USACCUM_IBIT 4)
+assert_min_bits(UACCUM_IBIT 4)
+assert_min_bits(ULACCUM_IBIT 4)
+
# Each unsigned fract type has either the same number of fractional bits as,
# or one more fractional bit than, its corresponding signed fract type.
-# TODO: Implement remaining checks in clause 6.2.6.3.
-function(check_diff_at_most_1 sfract_fbits ufract_fbits)
- if(sfract_fbits EQUAL ufract_fbits)
-return()
- endif()
+function(assert_fract_diff sfract_fbits ufract_fbits)
math(EXPR diff "${ufract_fbits} - ${sfract_fbits}")
- if(diff EQUAL 1)
-return()
+ if(NOT((${diff} EQUAL 0) OR (${diff} EQUAL 1)))
+message(FATAL_ERROR "Each unsigned fract type must have either the same number of "
+ "fractional bits as, or one more fractional bit than, its corresponding "
+ "signed fract type.")
+ endif()
+endfunction()
+
+assert_fract_diff(${SFRACT_FBIT} ${USFRACT_FBIT})
+assert_fract_diff(${FRACT_FBIT} ${UFRACT_FBIT})
+assert_fract_diff(${LFRACT_FBIT} ${ULFRACT_FBIT})
+
+# When arranged in order of increasing rank (see 6.3.1.3a), the number of
+# fractional bits is nondecreasing for each of the following sets of
+# fixed-point types:
+# - signed fract types
+# - unsigned fract types
+# - signed accum types
+# - unsigned accum types.
+function(assert_non_decreasing short_type_bits middle_type_bits long_type_bits
+ type_family bit_type)
+ if((${short_type_bits} GREATER ${middle_type_bits}) OR
+ (${middle_type_bits} GREATER ${long_type_bits}))
+message(FATAL_ERROR "The number of ${bit_type} bits in ${type_family} types must be "
+ "non decreasing in order of increasing rank.")
+ endif()
+endfunction()
+
+assert_non_decreasing(${SFRACT_FBIT} ${FRACT_FBIT} ${LFRACT_FBIT} "signed _Fract" "fractional")
+assert_non_decreasing(${USFRACT_FBIT} ${UFRACT_FBIT} ${ULFRACT_FBIT} "unsigned _Fract" "fractional")
+assert_non_decreasing(${SACCUM_FBIT} ${ACCUM_FBIT} ${LACCUM_FBIT} "signed _Accum" "fractional")
+assert_non_decreasing(${USACCUM_FBIT} ${UACCUM_FBIT} ${ULACCUM_FBIT} "unsigned _Accum" "fractional")
+
+# When arranged in order of increasing rank (see 6.3.1.3a), the number of
+# integral bits is nondecreasing for each of the following sets of
+# fixed-point types:
+# - signed accum types
+# - unsigned accum types.
+assert_non_decreasing(${SACCUM_IBIT} ${ACCUM_IBIT} ${LACCUM_IBIT} "signed _Accum" "integral")
+assert_non_decreasing(${USACCUM_IBIT} ${UACCUM_IBIT} ${ULACCUM_IBIT} "unsigned _Accum" "integral")
+
+# Each signed accum type has at least as many integral bits as its
+# corresponding unsigned accum type.
+function(assert_integral_diff saccum_ibits uaccum_ibits)
+ if(${saccum_ibits} LESS ${uaccum_ibits})
+message(FATAL_ERROR "Each signed accum type must have at least as many integral bits as its "
+ "corresponding unsigned accum type.")
+ endif()
+endfunction()
+
+assert_integral_diff(${SACCUM_IBIT} ${USACCUM_IBIT})
+assert_integral_diff(${ACCUM_IBIT}
