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

["Jan Beulich" <JBeulich@suse.com>]

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>}"
+}