Clang 9 bug workaround #3
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Clang 9 has a bug in which it reports a `GCC_VERSION` greater than or equal to 300 yet does not implement `__builtin_constant_p` as does GCC. This workaround ensures that `__builtin_constant_p` is not used when building with Clang 9. For more details, refer to the linked GCC bug [1]. Note that this workaround is required for building GCC 10.3 on the macOS 11 and above. [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92061 Signed-off-by: Stephanos Ioannidis <root@stephanos.io>
stephanosio
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Jan 6, 2022
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Verified working: https://github.com/zephyrproject-rtos/sdk-ng/runs/4727476915
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This patch makes us avoid substituting into the TEMPLATE_PARM_CONSTRAINTS of each template parameter except as necessary for declaration matching, like we already do for the other constituent constraints of a declaration. This patch also improves the CA104 implementation of explicit specialization matching of a constrained function template inside a class template, by considering the function's combined constraints instead of just its trailing constraints. This allows us to correctly handle the first three explicit specializations in concepts-spec2.C below, but because we compare the constraints as a whole, it means we incorrectly accept the fourth explicit specialization which writes #3's constraints in a different way. For complete correctness here, determine_specialization should use tsubst_each_template_parm_constraints and template_parameter_heads_equivalent_p. PR c++/100374 gcc/cp/ChangeLog: * pt.cc (determine_specialization): Compare overall constraints not just the trailing constraints. (tsubst_each_template_parm_constraints): Define. (tsubst_friend_function): Use it. (tsubst_friend_class): Use it. (tsubst_template_parm): Don't substitute TEMPLATE_PARM_CONSTRAINTS. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-spec2.C: New test. * g++.dg/cpp2a/concepts-template-parm11.C: New test. (cherry picked from commit 43c013d)
nashif
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May 31, 2025
…o_debug_section [PR116614]
cat abc.C
#define A(n) struct T##n {} t##n;
#define B(n) A(n##0) A(n##1) A(n##2) A(n##3) A(n##4) A(n##5) A(n##6) A(n##7) A(n##8) A(n##9)
#define C(n) B(n##0) B(n##1) B(n##2) B(n##3) B(n##4) B(n##5) B(n##6) B(n##7) B(n##8) B(n##9)
#define D(n) C(n##0) C(n##1) C(n##2) C(n##3) C(n##4) C(n##5) C(n##6) C(n##7) C(n##8) C(n##9)
#define E(n) D(n##0) D(n##1) D(n##2) D(n##3) D(n##4) D(n##5) D(n##6) D(n##7) D(n##8) D(n##9)
E(1) E(2) E(3)
int main () { return 0; }
./xg++ -B ./ -o abc{.o,.C} -flto -flto-partition=1to1 -O2 -g -fdebug-types-section -c
./xgcc -B ./ -o abc{,.o} -flto -flto-partition=1to1 -O2
(not included in testsuite as it takes a while to compile) FAILs with
lto-wrapper: fatal error: Too many copied sections: Operation not supported
compilation terminated.
/usr/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status
The following patch fixes that. Most of the 64K+ section support for
reading and writing was already there years ago (and especially reading used
quite often already) and a further bug fixed in it in the PR104617 fix.
Yet, the fix isn't solely about removing the
if (new_i - 1 >= SHN_LORESERVE)
{
*err = ENOTSUP;
return "Too many copied sections";
}
5 lines, the missing part was that the function only handled reading of
the .symtab_shndx section but not copying/updating of it.
If the result has less than 64K-epsilon sections, that actually wasn't
needed, but e.g. with -fdebug-types-section one can exceed that pretty
easily (reported to us on WebKitGtk build on ppc64le).
Updating the section is slightly more complicated, because it basically
needs to be done in lock step with updating the .symtab section, if one
doesn't need to use SHN_XINDEX in there, the section should (or should be
updated to) contain SHN_UNDEF entry, otherwise needs to have whatever would
be overwise stored but couldn't fit. But repeating due to that all the
symtab decisions what to discard and how to rewrite it would be ugly.
So, the patch instead emits the .symtab_shndx section (or sections) last
and prepares the content during the .symtab processing and in a second
pass when going just through .symtab_shndx sections just uses the saved
content.
2024-09-07 Jakub Jelinek <jakub@redhat.com>
PR lto/116614
* simple-object-elf.c (SHN_COMMON): Align comment with neighbouring
comments.
(SHN_HIRESERVE): Use uppercase hex digits instead of lowercase for
consistency.
(simple_object_elf_find_sections): Formatting fixes.
(simple_object_elf_fetch_attributes): Likewise.
(simple_object_elf_attributes_merge): Likewise.
(simple_object_elf_start_write): Likewise.
(simple_object_elf_write_ehdr): Likewise.
(simple_object_elf_write_shdr): Likewise.
(simple_object_elf_write_to_file): Likewise.
(simple_object_elf_copy_lto_debug_section): Likewise. Don't fail for
new_i - 1 >= SHN_LORESERVE, instead arrange in that case to copy
over .symtab_shndx sections, though emit those last and compute their
section content when processing associated .symtab sections. Handle
simple_object_internal_read failure even in the .symtab_shndx reading
case.
(cherry picked from commit bb8dd09)
nashif
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that referenced
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May 31, 2025
Whenever C1 and C2 are integer constants, X is of a wrapping type, and cmp is a relational operator, the expression X +- C1 cmp C2 can be simplified in the following cases: (a) If cmp is <= and C2 -+ C1 == +INF(1), we can transform the initial comparison in the following way: X +- C1 <= C2 -INF <= X +- C1 <= C2 (add left hand side which holds for any X, C1) -INF -+ C1 <= X <= C2 -+ C1 (add -+C1 to all 3 expressions) -INF -+ C1 <= X <= +INF (due to (1)) -INF -+ C1 <= X (eliminate the right hand side since it holds for any X) (b) By analogy, if cmp if >= and C2 -+ C1 == -INF(1), use the following sequence of transformations: X +- C1 >= C2 +INF >= X +- C1 >= C2 (add left hand side which holds for any X, C1) +INF -+ C1 >= X >= C2 -+ C1 (add -+C1 to all 3 expressions) +INF -+ C1 >= X >= -INF (due to (1)) +INF -+ C1 >= X (eliminate the right hand side since it holds for any X) (c) The > and < cases are negations of (a) and (b), respectively. This transformation allows to occasionally save add / sub instructions, for instance the expression 3 + (uint32_t)f() < 2 compiles to cmn w0, #4 cset w0, ls instead of add w0, w0, 3 cmp w0, 2 cset w0, ls on aarch64. Testcases that go together with this patch have been split into two separate files, one containing testcases for unsigned variables and the other for wrapping signed ones (and thus compiled with -fwrapv). Additionally, one aarch64 test has been adjusted since the patch has caused the generated code to change from cmn w0, #2 csinc w0, w1, wzr, cc (x < -2) to cmn w0, #3 csinc w0, w1, wzr, cs (x <= -3) This patch has been bootstrapped and regtested on aarch64, x86_64, and i386, and additionally regtested on riscv32. gcc/ChangeLog: PR tree-optimization/116024 * match.pd: New transformation around integer comparison. gcc/testsuite/ChangeLog: * gcc.dg/tree-ssa/pr116024-2.c: New test. * gcc.dg/tree-ssa/pr116024-2-fwrapv.c: Ditto. * gcc.target/aarch64/gtu_to_ltu_cmp_1.c: Adjust.
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Clang 9 has a bug in which it reports a
GCC_VERSIONgreater than orequal to 300 yet does not implement
__builtin_constant_pas does GCC.This workaround ensures that
__builtin_constant_pis not used whenbuilding with Clang 9.
For more details, refer to the linked GCC bug [1].
Note that this workaround is required for building GCC 10.3 on the
macOS 11 and above.
[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92061
Signed-off-by: Stephanos Ioannidis root@stephanos.io