[PATCH v2] x86-64: fix ZMM register state tracking

Jan Beulich
2018-10-10T15:12:18Z

The three AVX512 state components are entirely independent - one being
in its "init state" has no implication whatsoever on either of the other
two. Fully separate X86_XSTATE_ZMM_H and X86_XSTATE_ZMM handling, to
prevent upper halves of the upper 16 ZMM registers to display as if they
were zero (when they aren't) after e.g. VZEROALL/VZEROUPPER.

gdb/
2018-10-10 Jan Beulich <jbeulich@suse.com>

* i387-tdep.c (i387_supply_xsave): Split handling of
X86_XSTATE_ZMM_H and X86_XSTATE_ZMM.
(i387_collect_xsave): Likewise.

gdb/testsuite/
2018-10-10 Simon Marchi <simon.marchi@polymtl.ca>

* testsuite/gdb.arch/i386-avx512.c,
testsuite/gdb.arch/i386-avx512.exp: Add 7th test.

---
v2: Attach comments to zmm_endlo_regnum declarations. Add testcase
provided by Simon.

--- a/gdb/i387-tdep.c
+++ b/gdb/i387-tdep.c
@@ -924,6 +924,12 @@ i387_supply_xsave (struct regcache *regc
struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
const gdb_byte *regs = (const gdb_byte *) xsave;
int i;
+ /* In 64-bit mode the split between "low" and "high" ZMM registers is at
+ ZMM16. Outside of 64-bit mode there are no "high" ZMM registers at all.
+ Precalculate the number to be used for the split point, with the all
+ registers in the "low" portion outside of 64-bit mode. */
+ unsigned int zmm_endlo_regnum = I387_ZMM0H_REGNUM (tdep)
+ + std::min (tdep->num_zmm_regs, 16);
ULONGEST clear_bv;
static const gdb_byte zero[I386_MAX_REGISTER_SIZE] = { 0 };
enum
@@ -1002,7 +1008,8 @@ i387_supply_xsave (struct regcache *regc
return;

case avx512_zmm_h:
- if ((clear_bv & (X86_XSTATE_ZMM_H | X86_XSTATE_ZMM)))
+ if ((clear_bv & (regnum < zmm_endlo_regnum ? X86_XSTATE_ZMM_H
+ : X86_XSTATE_ZMM)))
regcache->raw_supply (regnum, zero);
else
regcache->raw_supply (regnum,
@@ -1080,21 +1087,17 @@ i387_supply_xsave (struct regcache *regc
}
}

- /* Handle the upper ZMM registers. */
- if ((tdep->xcr0 & (X86_XSTATE_ZMM_H | X86_XSTATE_ZMM)))
+ /* Handle the upper halves of the low 8/16 ZMM registers. */
+ if ((tdep->xcr0 & X86_XSTATE_ZMM_H))
{
- if ((clear_bv & (X86_XSTATE_ZMM_H | X86_XSTATE_ZMM)))
+ if ((clear_bv & X86_XSTATE_ZMM_H))
{
- for (i = I387_ZMM0H_REGNUM (tdep);
- i < I387_ZMMENDH_REGNUM (tdep);
- i++)
+ for (i = I387_ZMM0H_REGNUM (tdep); i < zmm_endlo_regnum; i++)
regcache->raw_supply (i, zero);
}
else
{
- for (i = I387_ZMM0H_REGNUM (tdep);
- i < I387_ZMMENDH_REGNUM (tdep);
- i++)
+ for (i = I387_ZMM0H_REGNUM (tdep); i < zmm_endlo_regnum; i++)
regcache->raw_supply (i,
XSAVE_AVX512_ZMM_H_ADDR (tdep, regs, i));
}
@@ -1119,11 +1122,13 @@ i387_supply_xsave (struct regcache *regc
}
}

- /* Handle the YMM_AVX512 registers. */
+ /* Handle the upper 16 ZMM/YMM/XMM registers (if any). */
if ((tdep->xcr0 & X86_XSTATE_ZMM))
{
if ((clear_bv & X86_XSTATE_ZMM))
{
+ for (i = zmm_endlo_regnum; i < I387_ZMMENDH_REGNUM (tdep); i++)
+ regcache->raw_supply (i, zero);
for (i = I387_YMM16H_REGNUM (tdep);
i < I387_YMMH_AVX512_END_REGNUM (tdep);
i++)
@@ -1135,6 +1140,9 @@ i387_supply_xsave (struct regcache *regc
}
else
{
+ for (i = zmm_endlo_regnum; i < I387_ZMMENDH_REGNUM (tdep); i++)
+ regcache->raw_supply (i,
+ XSAVE_AVX512_ZMM_H_ADDR (tdep, regs, i));
for (i = I387_YMM16H_REGNUM (tdep);
i < I387_YMMH_AVX512_END_REGNUM (tdep);
i++)
@@ -1341,6 +1349,9 @@ i387_collect_xsave (const struct regcach
gdb_byte raw[I386_MAX_REGISTER_SIZE];
ULONGEST initial_xstate_bv, clear_bv, xstate_bv = 0;
unsigned int i;
+ /* See the comment in i387_supply_xsave(). */
+ unsigned int zmm_endlo_regnum = I387_ZMM0H_REGNUM (tdep)
+ + std::min (tdep->num_zmm_regs, 16);
enum
{
x87_ctrl_or_mxcsr = 0x1,
@@ -1441,9 +1452,8 @@ i387_collect_xsave (const struct regcach
i < I387_MPXEND_REGNUM (tdep); i++)
memset (XSAVE_MPX_ADDR (tdep, regs, i), 0, 8);

- if ((clear_bv & (X86_XSTATE_ZMM_H | X86_XSTATE_ZMM)))
- for (i = I387_ZMM0H_REGNUM (tdep);
- i < I387_ZMMENDH_REGNUM (tdep); i++)
+ if ((clear_bv & X86_XSTATE_ZMM_H))
+ for (i = I387_ZMM0H_REGNUM (tdep); i < zmm_endlo_regnum; i++)
memset (XSAVE_AVX512_ZMM_H_ADDR (tdep, regs, i), 0, 32);

if ((clear_bv & X86_XSTATE_K))
@@ -1453,6 +1463,8 @@ i387_collect_xsave (const struct regcach

if ((clear_bv & X86_XSTATE_ZMM))
{
+ for (i = zmm_endlo_regnum; i < I387_ZMMENDH_REGNUM (tdep); i++)
+ memset (XSAVE_AVX512_ZMM_H_ADDR (tdep, regs, i), 0, 32);
for (i = I387_YMM16H_REGNUM (tdep);
i < I387_YMMH_AVX512_END_REGNUM (tdep); i++)
memset (XSAVE_YMM_AVX512_ADDR (tdep, regs, i), 0, 16);
--- a/gdb/testsuite/gdb.arch/i386-avx512.c
+++ b/gdb/testsuite/gdb.arch/i386-avx512.c
@@ -249,6 +249,13 @@ main (int argc, char **argv)
move back to array and check values. */
move_zmm_data_to_memory ();
asm ("nop"); /* sixth breakpoint here */
+
+ asm ("vpternlogd $0xff, %zmm0, %zmm0, %zmm0");
+#ifdef __x86_64__
+ asm ("vpternlogd $0xff, %zmm0, %zmm0, %zmm16");
+#endif
+ asm ("vzeroupper");
+ asm ("nop"); /* seventh breakpoint here */
}

return 0;
--- a/gdb/testsuite/gdb.arch/i386-avx512.exp
+++ b/gdb/testsuite/gdb.arch/i386-avx512.exp
@@ -174,3 +174,13 @@ for { set r 0 } { $r < $nr_regs } { incr
".. = \\{f = \\{[expr $r + 30], [expr $r.125 + 30], [expr $r.25 + 20], [expr $r.375 + 20], [expr $r.5 + 10], [expr $r.625 + 10], [expr $r.75 + 10], [expr $r.875 + 10]\\}\\}.*" \
"check contents of zmm_data\[$r\] after writing XMM regs"
}
+
+gdb_test "break [gdb_get_line_number "seventh breakpoint here"]" \
+ "Breakpoint .* at .*i386-avx512.c.*" \
+ "set seventh breakpoint in main"
+gdb_continue_to_breakpoint "continue to seventh breakpoint in main"
+gdb_test "print \$zmm0.v16_int32" "= {-1, -1, -1, -1, 0 <repeats 12 times>}"
+
+if { $nr_regs >= 16 } {
+ gdb_test "print \$zmm16.v16_int32" "= {-1 <repeats 16 times>}"
+}