[Bug bootstrap/92433] [10 regression] r276645 breaks bootstrap on powerpc
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92433 Jakub Jelinek changed: What|Removed |Added Status|UNCONFIRMED |RESOLVED Resolution|--- |FIXED Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org --- Comment #8 from Jakub Jelinek --- Should be fixed now.
[Bug bootstrap/92433] [10 regression] r276645 breaks bootstrap on powerpc
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92433 --- Comment #7 from Jakub Jelinek --- Author: jakub Date: Mon Nov 11 20:05:49 2019 New Revision: 278066 URL: https://gcc.gnu.org/viewcvs?rev=278066=gcc=rev Log: PR bootstrap/92433 * config/rs6000/rs6000-c.c (altivec_build_resolved_builtin): Guard ALTIVEC_BUILTIN_VEC_VCMPGE_P argument swapping with n == 3 check. Use std::swap. Modified: trunk/gcc/ChangeLog trunk/gcc/config/rs6000/rs6000-c.c
[Bug bootstrap/92433] [10 regression] r276645 breaks bootstrap on powerpc
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92433
--- Comment #6 from Jakub Jelinek ---
(In reply to Segher Boessenkool from comment #5)
> if (y)
> {
> gcc_assert (n == 3);
> std::swap (arg_type[1], arg_type[2]);
> }
>
>
> ?
gcc_assert will work too unless the host compiler is older than 4.5 (or is
clang), but I think we don't really make -Werror on in that case, at least not
by default (only in second stage that is built with trunk gcc already).
So, I can bootstrap/regtest:
2019-11-11 Jakub Jelinek
PR bootstrap/92433
* config/rs6000/rs6000-c.c (altivec_build_resolved_builtin): Add
assertion that n is 3 for ALTIVEC_BUILTIN_VEC_VCMPGE_P. Use
std::swap.
--- gcc/config/rs6000/rs6000-c.c.jj 2019-08-27 12:26:30.115019661 +0200
+++ gcc/config/rs6000/rs6000-c.c2019-11-11 15:03:57.299102261 +0100
@@ -6080,10 +6080,10 @@ altivec_build_resolved_builtin (tree *ar
&& desc->overloaded_code != ALTIVEC_BUILTIN_VCMPGEFP_P
&& desc->overloaded_code != VSX_BUILTIN_XVCMPGEDP_P)
{
- tree t;
- t = args[2], args[2] = args[1], args[1] = t;
- t = arg_type[2], arg_type[2] = arg_type[1], arg_type[1] = t;
-
+ gcc_assert (n == 3);
+ std::swap (args[1], args[2]);
+ std::swap (arg_type[1], arg_type[2]);
+
args[0] = fold_build2 (BIT_XOR_EXPR, TREE_TYPE (args[0]), args[0],
build_int_cst (NULL_TREE, 2));
}
too if you prefer it that way. Richi said on IRC he prefers a rs6000-c.c
change in this case.
[Bug bootstrap/92433] [10 regression] r276645 breaks bootstrap on powerpc
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92433
--- Comment #5 from Segher Boessenkool ---
if (y)
{
gcc_assert (n == 3);
std::swap (arg_type[1], arg_type[2]);
}
?
[Bug bootstrap/92433] [10 regression] r276645 breaks bootstrap on powerpc
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92433
--- Comment #4 from Jakub Jelinek ---
Reduced testcase that results in the warning also on x86_64-linux with -O2
-Wall:
struct S { void *p; struct S *q; };
void bar (int, ...);
void
foo (struct S *x, int n, int y)
{
void *arg_type[3];
for (int i = 0; i < n; i++)
{
arg_type[i] = x->p;
x = x->q;
}
if (y)
{
void *t = arg_type[2]; arg_type[2] = arg_type[1]; arg_type[1] = t;
}
switch (n)
{
case 0: bar (0); break;
case 1: bar (1, arg_type[0]); break;
case 2: bar (2, arg_type[0], arg_type[1]); break;
case 3: bar (3, arg_type[0], arg_type[1], arg_type[2]); break;
}
}
Using if (n == 3 && y) makes the warning go away.
The compiler indeed doesn't know if y implies n == 3, although the caller
guarantees it.
So, we could do:
--- gcc/config/rs6000/rs6000-c.c.jj 2019-08-27 12:26:30.115019661 +0200
+++ gcc/config/rs6000/rs6000-c.c2019-11-11 10:12:00.954282097 +0100
@@ -6076,13 +6076,13 @@ altivec_build_resolved_builtin (tree *ar
condition (LT vs. EQ, which is recognizable by bit 1 of the first
argument) is reversed. Patch the arguments here before building
the resolved CALL_EXPR. */
- if (desc->code == ALTIVEC_BUILTIN_VEC_VCMPGE_P
+ if (n == 3
+ && desc->code == ALTIVEC_BUILTIN_VEC_VCMPGE_P
&& desc->overloaded_code != ALTIVEC_BUILTIN_VCMPGEFP_P
&& desc->overloaded_code != VSX_BUILTIN_XVCMPGEDP_P)
{
- tree t;
- t = args[2], args[2] = args[1], args[1] = t;
- t = arg_type[2], arg_type[2] = arg_type[1], arg_type[1] = t;
+ std::swap (args[1], args[2]);
+ std::swap (arg_type[1], arg_type[2]);
args[0] = fold_build2 (BIT_XOR_EXPR, TREE_TYPE (args[0]), args[0],
build_int_cst (NULL_TREE, 2));
to make it clear to the compiler that VCMPGE_P has 3 arguments and that it is
actually safe to use all of them, or of course we could clear arg_type first.
I don't find the may be used uninitialized warning wrong (at least not
completely) when the compiler sees a possible code path where it is
uninitialized (desc->code == ALTIVEC_BULTIN_VEC_VCMPGE_P with n < 3).
[Bug bootstrap/92433] [10 regression] r276645 breaks bootstrap on powerpc
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92433 --- Comment #3 from Jakub Jelinek --- (In reply to Andreas Schwab from comment #2) > That doesn't fix the spurious warning, though. Sure, it doesn't, that was just a random comment when I have spent a minute looking at the code in question.
[Bug bootstrap/92433] [10 regression] r276645 breaks bootstrap on powerpc
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92433 Richard Biener changed: What|Removed |Added CC||rguenth at gcc dot gnu.org Blocks||24639 Target Milestone|--- |10.0 Referenced Bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24639 [Bug 24639] [meta-bug] bug to track all Wuninitialized issues
[Bug bootstrap/92433] [10 regression] r276645 breaks bootstrap on powerpc
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92433 --- Comment #2 from Andreas Schwab --- That doesn't fix the spurious warning, though.
[Bug bootstrap/92433] [10 regression] r276645 breaks bootstrap on powerpc
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92433 Jakub Jelinek changed: What|Removed |Added CC||jakub at gcc dot gnu.org, ||segher at gcc dot gnu.org --- Comment #1 from Jakub Jelinek --- The: tree t; t = args[2], args[2] = args[1], args[1] = t; t = arg_type[2], arg_type[2] = arg_type[1], arg_type[1] = t; would be much clearer if written as: std::swap (args[1], args[2]); std::swap (arg_type[1], arg_type[2]);
