Many places need to know the maximum or minimum possible value for a
given size integer... so everyone just open-codes their favorite
version. There is some potential to hit either undefined or
implementation-defined behavior, so having one version that Just Works
seems beneficial.
v2: Fix copy-and-pasted bug (INT64_MAX instead of INT64_MIN) in
u_intmin. Noticed by CI. Lol. Rename functions
`s/u_(uint|int)(min|max)/u_\1N_\2/g`. Suggested by Jason. Add some
unit tests that would have caught the copy-and-paste bug before wasting
CI time. Change the implementation of u_intN_min to use the same
pattern as stdint.h. This avoids the integer division. Noticed by
Jason.
v3: Add changes to convert_clear_color
(src/gallium/drivers/iris/iris_clear.c). Suggested by Nanley.
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Suggested-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12177>
Shifting int64_t values left into the sign bit has undefined behaviour:
../src/util/fast_idiv_by_const.c:175:14: runtime error: left shift of 131 by 56 places cannot be represented in type 'long int'
#0 0x561337ed10c1 in sign_extend ../src/util/fast_idiv_by_const.c:175
#1 0x561337ed1335 in util_compute_fast_sdiv_info ../src/util/fast_idiv_by_const.c:239
#2 0x561337e17519 in fast_idiv_by_const_int8_Test::TestBody() ../src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test.cpp:357
#3 0x561337ea815d in void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) ../src/gtest/src/gtest.cc:2402
#4 0x561337e93a6b in void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) ../src/gtest/src/gtest.cc:2438
#5 0x561337e38e75 in testing::Test::Run() ../src/gtest/src/gtest.cc:2474
#6 0x561337e3b54e in testing::TestInfo::Run() ../src/gtest/src/gtest.cc:2656
#7 0x561337e3dcdc in testing::TestCase::Run() ../src/gtest/src/gtest.cc:2774
#8 0x561337e596b6 in testing::internal::UnitTestImpl::RunAllTests() ../src/gtest/src/gtest.cc:4649
#9 0x561337eabd76 in bool testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) ../src/gtest/src/gtest.cc:2402
#10 0x561337e97443 in bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) ../src/gtest/src/gtest.cc:2438
#11 0x561337e50cd8 in testing::UnitTest::Run() ../src/gtest/src/gtest.cc:4257
#12 0x561337ed0b91 in RUN_ALL_TESTS() ../src/gtest/include/gtest/gtest.h:2233
#13 0x561337ed0a51 in main ../src/gtest/src/gtest_main.cc:37
#14 0x7f85ba483bba in __libc_start_main ../csu/libc-start.c:308
#15 0x561337e14dc9 in _start (/home/daenzer/src/mesa-git/mesa/build-amd64-sanitize/src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test+0x96dc9)
../src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test.cpp:51:14: runtime error: left shift of negative value -63
#0 0x55fc3c0e67cc in strunc ../src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test.cpp:51
#1 0x55fc3c0e6d93 in smul_high ../src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test.cpp:140
#2 0x55fc3c0e7067 in fast_sdiv ../src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test.cpp:181
#3 0x55fc3c0e858b in fast_idiv_by_const_int8_Test::TestBody() ../src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test.cpp:358
#4 0x55fc3c17915d in void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) ../src/gtest/src/gtest.cc:2402
#5 0x55fc3c164a6b in void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) ../src/gtest/src/gtest.cc:2438
#6 0x55fc3c109e75 in testing::Test::Run() ../src/gtest/src/gtest.cc:2474
#7 0x55fc3c10c54e in testing::TestInfo::Run() ../src/gtest/src/gtest.cc:2656
#8 0x55fc3c10ecdc in testing::TestCase::Run() ../src/gtest/src/gtest.cc:2774
#9 0x55fc3c12a6b6 in testing::internal::UnitTestImpl::RunAllTests() ../src/gtest/src/gtest.cc:4649
#10 0x55fc3c17cd76 in bool testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) ../src/gtest/src/gtest.cc:2402
#11 0x55fc3c168443 in bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) ../src/gtest/src/gtest.cc:2438
#12 0x55fc3c121cd8 in testing::UnitTest::Run() ../src/gtest/src/gtest.cc:4257
#13 0x55fc3c1a1b91 in RUN_ALL_TESTS() ../src/gtest/include/gtest/gtest.h:2233
#14 0x55fc3c1a1a51 in main ../src/gtest/src/gtest_main.cc:37
#15 0x7fd224759bba in __libc_start_main ../csu/libc-start.c:308
#16 0x55fc3c0e5dc9 in _start (/home/daenzer/src/mesa-git/mesa/build-amd64-sanitize/src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test+0x96dc9)
v2:
* Use two casts instead of changing the argument type (Jason Ekstrand)
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Adam Jackson <ajax@redhat.com>
There's nothing inherently fixed-width in the code. All that's required
to generalize it is to make everything internally 64-bit and pass
UINT_BITS in as a parameter to util_compute_fast_[us]div_info. With
that, it can now handle 8, 16, 32, and 64-bit integer division by a
constant.
We also add support for division by 1 and by other powers of 2. This is
useful if you want to divide by a uniform value in a shader where you
have the opportunity to adjust the uniform on the CPU before passing it
in.
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Compilers can use this to generate optimal code for integer division
by a constant.
Additionally, an unsigned division by a uniform that is constant but not
known at compile time can still be optimized by passing 2-4 division
factors to the shader as uniforms and executing one of the fast_udiv*
variants. The signed division algorithm doesn't have this capability.
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Jason Ekstrand
Ian Romanick
Michel Dänzer
Marek Olšák
Jason Ekstrand