nvptx: Don't use PTX '.const', constant state space [PR119573]

nvptx: Don't use PTX '.const', constant state space [PR119573]

This avoids cases where a "File uses too much global constant data" (final
executable, or single object file), and avoids cases of wrong code generation:
"error : State space incorrect for instruction 'st'" ('st.const'), or another
case where an "illegal instruction was encountered", or a lot of cases where
for two compilation units (such as a library linked with user code) we ran into
"error : Memory space doesn't match" due to differences in '.const' usage
between definition and use of a variable.

We progress:

    ptxas error   : File uses too much global constant data (0x1f01a bytes, 0x10000 max)
    nvptx-run: cuLinkAddData failed: a PTX JIT compilation failed (CUDA_ERROR_INVALID_PTX, 218)

... into:

    PASS: 20_util/to_chars/103955.cc  -std=gnu++17 (test for excess errors)
    [-FAIL:-]{+PASS:+} 20_util/to_chars/103955.cc  -std=gnu++17 execution test

We progress:

    ptxas error   : File uses too much global constant data (0x36c65 bytes, 0x10000 max)
    nvptx-as: ptxas returned 255 exit status

... into:

    [-UNSUPPORTED:-]{+PASS:+} gcc.c-torture/compile/pr46534.c   -O0  {+(test for excess errors)+}
    [-UNSUPPORTED:-]{+PASS:+} gcc.c-torture/compile/pr46534.c   -O1  {+(test for excess errors)+}
    [-UNSUPPORTED:-]{+PASS:+} gcc.c-torture/compile/pr46534.c   -O2  {+(test for excess errors)+}
    [-UNSUPPORTED:-]{+PASS:+} gcc.c-torture/compile/pr46534.c   -O3 -g  {+(test for excess errors)+}
    [-UNSUPPORTED:-]{+PASS:+} gcc.c-torture/compile/pr46534.c   -Os  {+(test for excess errors)+}

    [-FAIL:-]{+PASS:+} g++.dg/torture/pr31863.C   -O0  (test for excess errors)
    [-FAIL:-]{+PASS:+} g++.dg/torture/pr31863.C   -O1  (test for excess errors)
    [-FAIL:-]{+PASS:+} g++.dg/torture/pr31863.C   -O2  (test for excess errors)
    [-FAIL:-]{+PASS:+} g++.dg/torture/pr31863.C   -O3 -g  (test for excess errors)
    [-FAIL:-]{+PASS:+} g++.dg/torture/pr31863.C   -Os  (test for excess errors)

    [-FAIL:-]{+PASS:+} gfortran.dg/bind-c-contiguous-1.f90   -O0  (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} gfortran.dg/bind-c-contiguous-1.f90   -O0  [-compilation failed to produce executable-]{+execution test+}

    [-FAIL:-]{+PASS:+} gfortran.dg/bind-c-contiguous-4.f90   -O0  (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} gfortran.dg/bind-c-contiguous-4.f90   -O0  [-compilation failed to produce executable-]{+execution test+}

    [-FAIL:-]{+PASS:+} gfortran.dg/bind-c-contiguous-5.f90   -O0  (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} gfortran.dg/bind-c-contiguous-5.f90   -O0  [-compilation failed to produce executable-]{+execution test+}

    [-FAIL:-]{+PASS:+} 20_util/to_chars/double.cc  -std=gnu++17 (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} 20_util/to_chars/double.cc  -std=gnu++17 [-compilation failed to produce executable-]{+execution test+}

    [-FAIL:-]{+PASS:+} 20_util/to_chars/float.cc  -std=gnu++17 (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} 20_util/to_chars/float.cc  -std=gnu++17 [-compilation failed to produce executable-]{+execution test+}

    [-FAIL:-]{+PASS:+} special_functions/13_ellint_3/check_value.cc  -std=gnu++17 (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} special_functions/13_ellint_3/check_value.cc  -std=gnu++17 [-compilation failed to produce executable-]{+execution test+}

    [-FAIL:-]{+PASS:+} tr1/5_numerical_facilities/special_functions/14_ellint_3/check_value.cc  -std=gnu++17 (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} tr1/5_numerical_facilities/special_functions/14_ellint_3/check_value.cc  -std=gnu++17 [-compilation failed to produce executable-]{+execution test+}

..., and progress likewise, but fail later with an unrelated error:

    [-FAIL:-]{+PASS:+} ext/special_functions/hyperg/check_value.cc  -std=gnu++17 (test for excess errors)
    [-UNRESOLVED:-]{+FAIL:+} ext/special_functions/hyperg/check_value.cc  -std=gnu++17 [-compilation failed to produce executable-]{+execution test+}

    [...]/libstdc++-v3/testsuite/ext/special_functions/hyperg/check_value.cc:12317: void test(const testcase_hyperg<Ret> (&)[Num], Ret) [with Ret = double; unsigned int Num = 19]: Assertion 'max_abs_frac < toler' failed.

..., and:

    [-FAIL:-]{+PASS:+} tr1/5_numerical_facilities/special_functions/17_hyperg/check_value.cc  -std=gnu++17 (test for excess errors)
    [-UNRESOLVED:-]{+FAIL:+} tr1/5_numerical_facilities/special_functions/17_hyperg/check_value.cc  -std=gnu++17 [-compilation failed to produce executable-]{+execution test+}

    [...]/libstdc++-v3/testsuite/tr1/5_numerical_facilities/special_functions/17_hyperg/check_value.cc:12316: void test(const testcase_hyperg<Ret> (&)[Num], Ret) [with Ret = double; unsigned int Num = 19]: Assertion 'max_abs_frac < toler' failed.

We progress:

    nvptx-run: error getting kernel result: an illegal instruction was encountered (CUDA_ERROR_ILLEGAL_INSTRUCTION, 715)

... into:

    PASS: g++.dg/cpp1z/inline-var1.C  -std=gnu++17 (test for excess errors)
    [-FAIL:-]{+PASS:+} g++.dg/cpp1z/inline-var1.C  -std=gnu++17 execution test
    PASS: g++.dg/cpp1z/inline-var1.C  -std=gnu++20 (test for excess errors)
    [-FAIL:-]{+PASS:+} g++.dg/cpp1z/inline-var1.C  -std=gnu++20 execution test
    PASS: g++.dg/cpp1z/inline-var1.C  -std=gnu++26 (test for excess errors)
    [-FAIL:-]{+PASS:+} g++.dg/cpp1z/inline-var1.C  -std=gnu++26 execution test

(A lot of '.const' -> '.global' etc.  Haven't researched what the actual
problem was.)

We progress:

    ptxas /tmp/cc5TSZZp.o, line 142; error   : State space incorrect for instruction 'st'
    ptxas /tmp/cc5TSZZp.o, line 174; error   : State space incorrect for instruction 'st'
    ptxas fatal   : Ptx assembly aborted due to errors
    nvptx-as: ptxas returned 255 exit status

... into:

    [-FAIL:-]{+PASS:+} g++.dg/torture/builtin-clear-padding-1.C   -O0  (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} g++.dg/torture/builtin-clear-padding-1.C   -O0  [-compilation failed to produce executable-]{+execution test+}
    PASS: g++.dg/torture/builtin-clear-padding-1.C   -O1  (test for excess errors)
    PASS: g++.dg/torture/builtin-clear-padding-1.C   -O1  execution test
    [-FAIL:-]{+PASS:+} g++.dg/torture/builtin-clear-padding-1.C   -O2  (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} g++.dg/torture/builtin-clear-padding-1.C   -O2  [-compilation failed to produce executable-]{+execution test+}
    [-FAIL:-]{+PASS:+} g++.dg/torture/builtin-clear-padding-1.C   -O3 -g  (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} g++.dg/torture/builtin-clear-padding-1.C   -O3 -g  [-compilation failed to produce executable-]{+execution test+}
    [-FAIL:-]{+PASS:+} g++.dg/torture/builtin-clear-padding-1.C   -Os  (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} g++.dg/torture/builtin-clear-padding-1.C   -Os  [-compilation failed to produce executable-]{+execution test+}

This indeed tried to write ('st.const') into 's2', which was '.const'
(also: 's1' was '.const') -- even though, no explicit 'const' in
'g++.dg/torture/builtin-clear-padding-1.C'; "interesting".

We progress:

    error   : Memory space doesn't match for '_ZNSt3tr18__detail12__prime_listE' in 'input file 3 at offset 53085', first specified in 'input file 1 at offset 1924'
    nvptx-run: cuLinkAddData failed: device kernel image is invalid (CUDA_ERROR_INVALID_SOURCE, 300)

... into execution test PASS for a few dozens of libstdc++ test cases.

We progress:

    error   : Memory space doesn't match for '_ZNSt6locale17_S_twinned_facetsE' in 'input file 11 at offset 479903', first specified in 'input file 9 at offset 59300'
    nvptx-run: cuLinkAddData failed: device kernel image is invalid (CUDA_ERROR_INVALID_SOURCE, 300)

... into:

    PASS: g++.dg/tree-ssa/pr20458.C  -std=gnu++17 (test for excess errors)
    [-FAIL:-]{+PASS:+} g++.dg/tree-ssa/pr20458.C  -std=gnu++17 execution test
    PASS: g++.dg/tree-ssa/pr20458.C  -std=gnu++26 (test for excess errors)
    [-FAIL:-]{+PASS:+} g++.dg/tree-ssa/pr20458.C  -std=gnu++26 execution test

..., and likewise for a few hundreds of libstdc++ test cases.

We progress:

    error   : Memory space doesn't match for '_ZNSt6locale5_Impl19_S_facet_categoriesE' in 'input file 11 at offset 821962', first specified in 'input file 10 at offset 676317'
    nvptx-run: cuLinkAddData failed: device kernel image is invalid (CUDA_ERROR_INVALID_SOURCE, 300)

... into execution test PASS for a hundred of libstdc++ test cases.

We progress:

    error   : Memory space doesn't match for '_ctype_' in 'input file 22 at offset 1698331', first specified in 'input file 9 at offset 57095'
    nvptx-run: cuLinkAddData failed: device kernel image is invalid (CUDA_ERROR_INVALID_SOURCE, 300)

... into execution test PASS for another few libstdc++ test cases.

	PR target/119573
	gcc/
	* config/nvptx/nvptx.cc (nvptx_encode_section_info): Don't set
	'DATA_AREA_CONST' for 'TREE_CONSTANT', or 'TREE_READONLY'.
	(nvptx_asm_declare_constant_name): Use '.global' instead of
	'.const'.
	gcc/testsuite/
	* gcc.c-torture/compile/pr46534.c: Don't 'dg-skip-if' nvptx.
	* gcc.target/nvptx/decl.c: Adjust.
	libstdc++-v3/
	* config/cpu/nvptx/t-nvptx (AM_MAKEFLAGS): Don't amend.