* [PATCH] gimple-fold: fix location of loads for memory ops [PR104308]
@ 2022-03-25 21:26 David Malcolm
2022-03-28 8:29 ` Richard Biener
0 siblings, 1 reply; 2+ messages in thread
From: David Malcolm @ 2022-03-25 21:26 UTC (permalink / raw)
To: gcc-patches
PR analyzer/104308 reports that when -Wanalyzer-use-of-uninitialized-value
complains about certain memmove operations where the source is
uninitialized, the diagnostic uses UNKNOWN_LOCATION:
In function 'main':
cc1: warning: use of uninitialized value '*(short unsigned int *)&s + 1' [CWE-457] [-Wanalyzer-use-of-uninitialized-value]
'main': event 1
|
|pr104308.c:5:8:
| 5 | char s[5]; /* { dg-message "region created on stack here" } */
| | ^
| | |
| | (1) region created on stack here
|
'main': event 2
|
|cc1:
| (2): use of uninitialized value '*(short unsigned int *)&s + 1' here
|
The issue is that gimple_fold_builtin_memory_op converts a memmove to:
_3 = MEM <unsigned short> [(char * {ref-all})_1];
MEM <unsigned short> [(char * {ref-all})&s] = _3;
but only sets the location of the 2nd stmt, not the 1st.
Fixed thusly, giving:
pr104308.c: In function 'main':
pr104308.c:6:3: warning: use of uninitialized value '*(short unsigned int *)&s + 1' [CWE-457] [-Wanalyzer-use-of-uninitialized-value]
6 | memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" } */
| ^~~~~~~~~~~~~~~~~~~~
'main': events 1-2
|
| 5 | char s[5]; /* { dg-message "region created on stack here" } */
| | ^
| | |
| | (1) region created on stack here
| 6 | memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" } */
| | ~~~~~~~~~~~~~~~~~~~~
| | |
| | (2) use of uninitialized value '*(short unsigned int *)&s + 1' here
|
One side-effect of this change is a change in part of the output of
gcc.dg/uninit-40.c from:
uninit-40.c:47:3: warning: ‘*(long unsigned int *)(&u[1][0][0])’ is used uninitialized [-Wuninitialized]
47 | __builtin_memcpy (&v[1], &u[1], sizeof (V));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
uninit-40.c:45:5: note: ‘*(long unsigned int *)(&u[1][0][0])’ was declared here
45 | V u[2], v[2];
| ^
to:
uninit-40.c:47:3: warning: ‘u’ is used uninitialized [-Wuninitialized]
47 | __builtin_memcpy (&v[1], &u[1], sizeof (V));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
uninit-40.c:45:5: note: ‘u’ declared here
45 | V u[2], v[2];
| ^
What's happening is that pass "early_uninit"(29)'s call to
maybe_warn_operand is guarded by this condition:
1051 else if (gimple_assign_load_p (stmt)
1052 && gimple_has_location (stmt))
Before the patch, the stmt:
_3 = MEM <unsigned long> [(char * {ref-all})&u + 8B];
has no location, and so early_uninit skips this operand at line
1052 above. Later, pass "uninit"(217) tests the var_decl "u$8", and
emits a warning for it.
With the patch, the stmt has a location, and so early_uninit emits a
warning for "u" and sets a NW_UNINIT warning suppression at that
location. Later, pass "uninit"(217)'s test of "u$8" is rejected
due to that per-location suppression of uninit warnings, from the
earlier warning.
Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
OK for stage 4? or for next stage 1?
gcc/ChangeLog:
PR analyzer/104308
* gimple-fold.cc (gimple_fold_builtin_memory_op): When optimizing
to loads then stores, set the location of the new load stmt.
gcc/testsuite/ChangeLog:
PR analyzer/104308
* gcc.dg/analyzer/pr104308.c: New test.
* gcc.dg/uninit-40.c (foo): Update expression in expected message.
Signed-off-by: David Malcolm <dmalcolm@redhat.com>
---
gcc/gimple-fold.cc | 1 +
gcc/testsuite/gcc.dg/analyzer/pr104308.c | 8 ++++++++
gcc/testsuite/gcc.dg/uninit-40.c | 2 +-
3 files changed, 10 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/analyzer/pr104308.c
diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index 5eff7d68ac1..e73bc6a7137 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -1039,6 +1039,7 @@ gimple_fold_builtin_memory_op (gimple_stmt_iterator *gsi,
new_stmt);
gimple_assign_set_lhs (new_stmt, srcmem);
gimple_set_vuse (new_stmt, gimple_vuse (stmt));
+ gimple_set_location (new_stmt, loc);
gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
}
if (dest_align < GET_MODE_ALIGNMENT (mode))
diff --git a/gcc/testsuite/gcc.dg/analyzer/pr104308.c b/gcc/testsuite/gcc.dg/analyzer/pr104308.c
new file mode 100644
index 00000000000..9cd5ee6feee
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/pr104308.c
@@ -0,0 +1,8 @@
+#include <string.h>
+
+int main()
+{
+ char s[5]; /* { dg-message "region created on stack here" } */
+ memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" } */
+ return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/uninit-40.c b/gcc/testsuite/gcc.dg/uninit-40.c
index 8708079d397..567707a885e 100644
--- a/gcc/testsuite/gcc.dg/uninit-40.c
+++ b/gcc/testsuite/gcc.dg/uninit-40.c
@@ -44,7 +44,7 @@ foo (int *q)
/* memcpy folding is too target dependent to test it everywhere. */
V u[2], v[2];
u[0][0][0] = 1;
- __builtin_memcpy (&v[1], &u[1], sizeof (V)); /* { dg-warning "'\\*\\(\(long \)?long unsigned int \\*\\)\\(&u\\\[1\\\]\\\[0\\\]\\\[0\\\]\\)' is used uninitialized" "" { target i?86-*-* x86_64-*-* } } */
+ __builtin_memcpy (&v[1], &u[1], sizeof (V)); /* { dg-warning "'u' is used uninitialized" "" { target i?86-*-* x86_64-*-* } } */
baz (&v[1]);
#endif
}
--
2.26.3
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] gimple-fold: fix location of loads for memory ops [PR104308]
2022-03-25 21:26 [PATCH] gimple-fold: fix location of loads for memory ops [PR104308] David Malcolm
@ 2022-03-28 8:29 ` Richard Biener
0 siblings, 0 replies; 2+ messages in thread
From: Richard Biener @ 2022-03-28 8:29 UTC (permalink / raw)
To: David Malcolm; +Cc: GCC Patches
On Fri, Mar 25, 2022 at 10:27 PM David Malcolm via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> PR analyzer/104308 reports that when -Wanalyzer-use-of-uninitialized-value
> complains about certain memmove operations where the source is
> uninitialized, the diagnostic uses UNKNOWN_LOCATION:
>
> In function 'main':
> cc1: warning: use of uninitialized value '*(short unsigned int *)&s + 1' [CWE-457] [-Wanalyzer-use-of-uninitialized-value]
> 'main': event 1
> |
> |pr104308.c:5:8:
> | 5 | char s[5]; /* { dg-message "region created on stack here" } */
> | | ^
> | | |
> | | (1) region created on stack here
> |
> 'main': event 2
> |
> |cc1:
> | (2): use of uninitialized value '*(short unsigned int *)&s + 1' here
> |
>
> The issue is that gimple_fold_builtin_memory_op converts a memmove to:
>
> _3 = MEM <unsigned short> [(char * {ref-all})_1];
> MEM <unsigned short> [(char * {ref-all})&s] = _3;
>
> but only sets the location of the 2nd stmt, not the 1st.
>
> Fixed thusly, giving:
>
> pr104308.c: In function 'main':
> pr104308.c:6:3: warning: use of uninitialized value '*(short unsigned int *)&s + 1' [CWE-457] [-Wanalyzer-use-of-uninitialized-value]
> 6 | memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" } */
> | ^~~~~~~~~~~~~~~~~~~~
> 'main': events 1-2
> |
> | 5 | char s[5]; /* { dg-message "region created on stack here" } */
> | | ^
> | | |
> | | (1) region created on stack here
> | 6 | memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" } */
> | | ~~~~~~~~~~~~~~~~~~~~
> | | |
> | | (2) use of uninitialized value '*(short unsigned int *)&s + 1' here
> |
>
> One side-effect of this change is a change in part of the output of
> gcc.dg/uninit-40.c from:
>
> uninit-40.c:47:3: warning: ‘*(long unsigned int *)(&u[1][0][0])’ is used uninitialized [-Wuninitialized]
> 47 | __builtin_memcpy (&v[1], &u[1], sizeof (V));
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> uninit-40.c:45:5: note: ‘*(long unsigned int *)(&u[1][0][0])’ was declared here
> 45 | V u[2], v[2];
> | ^
>
> to:
>
> uninit-40.c:47:3: warning: ‘u’ is used uninitialized [-Wuninitialized]
> 47 | __builtin_memcpy (&v[1], &u[1], sizeof (V));
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> uninit-40.c:45:5: note: ‘u’ declared here
> 45 | V u[2], v[2];
> | ^
>
> What's happening is that pass "early_uninit"(29)'s call to
> maybe_warn_operand is guarded by this condition:
> 1051 else if (gimple_assign_load_p (stmt)
> 1052 && gimple_has_location (stmt))
>
> Before the patch, the stmt:
> _3 = MEM <unsigned long> [(char * {ref-all})&u + 8B];
> has no location, and so early_uninit skips this operand at line
> 1052 above. Later, pass "uninit"(217) tests the var_decl "u$8", and
> emits a warning for it.
>
> With the patch, the stmt has a location, and so early_uninit emits a
> warning for "u" and sets a NW_UNINIT warning suppression at that
> location. Later, pass "uninit"(217)'s test of "u$8" is rejected
> due to that per-location suppression of uninit warnings, from the
> earlier warning.
>
> Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
>
> OK for stage 4? or for next stage 1?
OK for stage4.
Thanks,
Richard.
> gcc/ChangeLog:
> PR analyzer/104308
> * gimple-fold.cc (gimple_fold_builtin_memory_op): When optimizing
> to loads then stores, set the location of the new load stmt.
>
> gcc/testsuite/ChangeLog:
> PR analyzer/104308
> * gcc.dg/analyzer/pr104308.c: New test.
> * gcc.dg/uninit-40.c (foo): Update expression in expected message.
>
> Signed-off-by: David Malcolm <dmalcolm@redhat.com>
> ---
> gcc/gimple-fold.cc | 1 +
> gcc/testsuite/gcc.dg/analyzer/pr104308.c | 8 ++++++++
> gcc/testsuite/gcc.dg/uninit-40.c | 2 +-
> 3 files changed, 10 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.dg/analyzer/pr104308.c
>
> diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
> index 5eff7d68ac1..e73bc6a7137 100644
> --- a/gcc/gimple-fold.cc
> +++ b/gcc/gimple-fold.cc
> @@ -1039,6 +1039,7 @@ gimple_fold_builtin_memory_op (gimple_stmt_iterator *gsi,
> new_stmt);
> gimple_assign_set_lhs (new_stmt, srcmem);
> gimple_set_vuse (new_stmt, gimple_vuse (stmt));
> + gimple_set_location (new_stmt, loc);
> gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
> }
> if (dest_align < GET_MODE_ALIGNMENT (mode))
> diff --git a/gcc/testsuite/gcc.dg/analyzer/pr104308.c b/gcc/testsuite/gcc.dg/analyzer/pr104308.c
> new file mode 100644
> index 00000000000..9cd5ee6feee
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/analyzer/pr104308.c
> @@ -0,0 +1,8 @@
> +#include <string.h>
> +
> +int main()
> +{
> + char s[5]; /* { dg-message "region created on stack here" } */
> + memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" } */
> + return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/uninit-40.c b/gcc/testsuite/gcc.dg/uninit-40.c
> index 8708079d397..567707a885e 100644
> --- a/gcc/testsuite/gcc.dg/uninit-40.c
> +++ b/gcc/testsuite/gcc.dg/uninit-40.c
> @@ -44,7 +44,7 @@ foo (int *q)
> /* memcpy folding is too target dependent to test it everywhere. */
> V u[2], v[2];
> u[0][0][0] = 1;
> - __builtin_memcpy (&v[1], &u[1], sizeof (V)); /* { dg-warning "'\\*\\(\(long \)?long unsigned int \\*\\)\\(&u\\\[1\\\]\\\[0\\\]\\\[0\\\]\\)' is used uninitialized" "" { target i?86-*-* x86_64-*-* } } */
> + __builtin_memcpy (&v[1], &u[1], sizeof (V)); /* { dg-warning "'u' is used uninitialized" "" { target i?86-*-* x86_64-*-* } } */
> baz (&v[1]);
> #endif
> }
> --
> 2.26.3
>
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