Hi,
On x86, a memory reference reference to a TLS address can be broken out
and stored in a register, for instance:
movq %fs:8+testYearsBC@tpoff, %rdx
Subsequently becomes:
pushq %rbp
leaq 8+testYearsBC@tpoff, %rbp
// later...
movq %fs:0(%rbp), %rdx
When it comes to representing this in Dwarf, mem_loc_descriptor is left
with the following RTL, which ix86_delegitimize_tls_address is unable to
handle as the symbol_ref has been swapped out with the temporary.
(plus:DI (unspec:DI [
(const_int 0 [0])
] UNSPEC_TP)
(reg/f:DI 6 bp [90]))
The UNSPEC_TP expression is checked, ix86_const_not_ok_for_debug_p
returns false as it only lets through UNSPEC_GOTOFF, and finally
const_ok_for_output is either not smart enough or does not have the
information needed to recognize that UNSPEC_TP is a TLS UNSPEC that
should be ignored. This results in informational warnings being fired
under -fchecking.
The entrypoint that triggers this warning to occur is that MEM codes are
first lowered with mem_loc_descriptor, with tls_mem_loc_descriptor only
being used if that failed. This patch switches that around so that TLS
memory expressions first call tls_mem_loc_descriptor, and only use
mem_loc_descriptor if that fails (which may result in UNSPEC warnings).
Bootstrapped and regression tested on x86_64-linux-gnu, I do also have a
sparc64-linux-gnu build at hand, but have not yet got the results to
check for a before/after comparison.
OK for mainline?
Regards
Iain
---
gcc/ChangeLog:
PR target/96347
* dwarf2out.c (is_tls_mem_loc): New.
(mem_loc_descriptor): Call tls_mem_loc_descriptor on TLS memory
expressions, fallback to mem_loc_descriptor if unsuccessful.
(loc_descriptor): Likewise.
gcc/testsuite/ChangeLog:
PR target/96347
* g++.dg/other/pr96347.C: New test.
---
gcc/dwarf2out.c | 30 ++++++++++----
gcc/testsuite/g++.dg/other/pr96347.C | 61 ++++++++++++++++++++++++++++
2 files changed, 84 insertions(+), 7 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/other/pr96347.C
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 9deca031fc2..093ceb23c7a 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -14435,6 +14435,20 @@ is_based_loc (const_rtx rtl)
&& CONST_INT_P (XEXP (rtl, 1)))));
}
+/* Return true if this MEM expression is for a TLS variable. */
+
+static bool
+is_tls_mem_loc (rtx mem)
+{
+ tree base;
+
+ if (MEM_EXPR (mem) == NULL_TREE || !MEM_OFFSET_KNOWN_P (mem))
+ return false;
+
+ base = get_base_address (MEM_EXPR (mem));
+ return (base && VAR_P (base) && DECL_THREAD_LOCAL_P (base));
+}
+
/* Try to handle TLS MEMs, for which mem_loc_descriptor on XEXP (mem, 0)
failed. */
@@ -15671,11 +15685,12 @@ mem_loc_descriptor (rtx rtl, machine_mode mode,
return mem_loc_result;
}
}
- mem_loc_result = mem_loc_descriptor (XEXP (rtl, 0),
- get_address_mode (rtl), mode,
- VAR_INIT_STATUS_INITIALIZED);
- if (mem_loc_result == NULL)
+ if (is_tls_mem_loc (rtl))
mem_loc_result = tls_mem_loc_descriptor (rtl);
+ if (mem_loc_result == NULL)
+ mem_loc_result = mem_loc_descriptor (XEXP (rtl, 0),
+ get_address_mode (rtl), mode,
+ VAR_INIT_STATUS_INITIALIZED);
if (mem_loc_result != NULL)
{
if (!is_a <scalar_int_mode> (mode, &int_mode)
@@ -16631,10 +16646,11 @@ loc_descriptor (rtx rtl, machine_mode mode,
break;
case MEM:
- loc_result = mem_loc_descriptor (XEXP (rtl, 0), get_address_mode (rtl),
- GET_MODE (rtl), initialized);
- if (loc_result == NULL)
+ if (is_tls_mem_loc (rtl))
loc_result = tls_mem_loc_descriptor (rtl);
+ if (loc_result == NULL)
+ loc_result = mem_loc_descriptor (XEXP (rtl, 0), get_address_mode (rtl),
+ GET_MODE (rtl), initialized);
if (loc_result == NULL)
{
rtx new_rtl = avoid_constant_pool_reference (rtl);
diff --git a/gcc/testsuite/g++.dg/other/pr96347.C
b/gcc/testsuite/g++.dg/other/pr96347.C
new file mode 100644
index 00000000000..414d10c73de
--- /dev/null
+++ b/gcc/testsuite/g++.dg/other/pr96347.C
@@ -0,0 +1,61 @@
+/* { dg-do compile { target c++11 } } */
+/* { dg-require-effective-target tls } */
+/* { dg-options "-O2 -g -fchecking" } */
+
+struct DArray
+{
+ __SIZE_TYPE__ length;
+ int *ptr;
+};
+
+__thread DArray testYearsBC;
+
+struct FilterResult
+{
+ DArray input;
+ bool primed;
+
+ static FilterResult Dthis (FilterResult &pthis, DArray r)
+ {
+ pthis.input = r;
+ return pthis;
+ }
+
+ int front (void)
+ {
+ if (input.length == 0)
+ __builtin_abort ();
+ return input.ptr[0];
+ }
+};
+
+FilterResult filter (DArray range)
+{
+ FilterResult retval;
+ FilterResult::Dthis (retval, range);
+ return retval;
+}
+
+DArray chain (DArray rs)
+{
+ return rs;
+}
+
+struct SysTime
+{
+ static SysTime Dthis (int);
+};
+
+int main (void)
+{
+ while (1)
+ {
+ FilterResult val;
+ __builtin_memset (&val, 0, sizeof (FilterResult));
+ val = filter (chain (testYearsBC));
+ int year = val.front ();
+ (void)year;
+ SysTime::Dthis (0);
+ }
+ return 0;
+}
--
2.25.1
