2012-03-05 Pedro Alves <palves@redhat.com>

	* i387-tdep.c (i387_supply_xsave): If we have an xsave buffer, and
	the register state is clear, supply explicit zero, instead of
	marking the register unavailable.

1 files changed, 54 insertions, 33 deletions

diff --git a/gdb/i387-tdep.c b/gdb/i387-tdep.c
index 27f3c5b..3fc344d 100644
--- a/gdb/i387-tdep.c
+++ b/gdb/i387-tdep.c
@@ -779,6 +779,7 @@ i387_supply_xsave (struct regcache *regcache, int regnum,
   const gdb_byte *regs = xsave;
   int i;
   unsigned int clear_bv;
+  static const gdb_byte zero[MAX_REGISTER_SIZE] = { 0 };
   const gdb_byte *p;
   enum
     {
@@ -818,6 +819,19 @@ i387_supply_xsave (struct regcache *regcache, int regnum,
   else
     clear_bv = I386_XSTATE_AVX_MASK;
 
+  /* With the delayed xsave mechanism, in between the program
+     starting, and the program accessing the vector registers for the
+     first time, the register's values are invalid.  The kernel
+     initializes register states to zero when they are set the first
+     time in a program.  This means that from the user-space programs'
+     perspective, it's the same as if the registers have always been
+     zero from the start of the program.  Therefore, the debugger
+     should provide the same illusion to the user.
+
+     Note however, the case when REGS is NULL is a different case.
+     That case means we do not have access to the x87 states, so we
+     should mark the registers as unavailable (by supplying NULL).  */
+
   switch (regclass)
     {
     case none:
@@ -825,26 +839,26 @@ i387_supply_xsave (struct regcache *regcache, int regnum,
 
     case avxh:
       if ((clear_bv & I386_XSTATE_AVX))
-	p = NULL;
+	regcache_raw_supply (regcache, regnum, regs == NULL ? NULL : zero);
       else
-	p = XSAVE_AVXH_ADDR (tdep, regs, regnum);
-      regcache_raw_supply (regcache, regnum, p);
+	regcache_raw_supply (regcache, regnum,
+			     XSAVE_AVXH_ADDR (tdep, regs, regnum));
       return;
 
     case sse:
       if ((clear_bv & I386_XSTATE_SSE))
-	p = NULL;
+	regcache_raw_supply (regcache, regnum, regs == NULL ? NULL : zero);
       else
-	p = FXSAVE_ADDR (tdep, regs, regnum);
-      regcache_raw_supply (regcache, regnum, p);
+	regcache_raw_supply (regcache, regnum,
+			     FXSAVE_ADDR (tdep, regs, regnum));
       return;
 
     case x87:
       if ((clear_bv & I386_XSTATE_X87))
-	p = NULL;
+	regcache_raw_supply (regcache, regnum, regs == NULL ? NULL : zero);
       else
-	p = FXSAVE_ADDR (tdep, regs, regnum);
-      regcache_raw_supply (regcache, regnum, p);
+	regcache_raw_supply (regcache, regnum,
+			     FXSAVE_ADDR (tdep, regs, regnum));
       return;
 
     case all:
@@ -852,16 +866,19 @@ i387_supply_xsave (struct regcache *regcache, int regnum,
       if ((tdep->xcr0 & I386_XSTATE_AVX))
 	{
 	  if ((clear_bv & I386_XSTATE_AVX))
-	    p = NULL;
+	    {
+	      for (i = I387_YMM0H_REGNUM (tdep);
+		   i < I387_YMMENDH_REGNUM (tdep);
+		   i++)
+		regcache_raw_supply (regcache, i, regs == NULL ? NULL : zero);
+	    }
 	  else
-	    p = regs;
-
-	  for (i = I387_YMM0H_REGNUM (tdep);
-	       i < I387_YMMENDH_REGNUM (tdep); i++)
 	    {
-	      if (p != NULL)
-		p = XSAVE_AVXH_ADDR (tdep, regs, i);
-	      regcache_raw_supply (regcache, i, p);
+	      for (i = I387_YMM0H_REGNUM (tdep);
+		   i < I387_YMMENDH_REGNUM (tdep);
+		   i++)
+		regcache_raw_supply (regcache, i,
+				     XSAVE_AVXH_ADDR (tdep, regs, i));
 	    }
 	}
 
@@ -869,16 +886,18 @@ i387_supply_xsave (struct regcache *regcache, int regnum,
       if ((tdep->xcr0 & I386_XSTATE_SSE))
 	{
 	  if ((clear_bv & I386_XSTATE_SSE))
-	    p = NULL;
+	    {
+	      for (i = I387_XMM0_REGNUM (tdep);
+		   i < I387_MXCSR_REGNUM (tdep);
+		   i++)
+		regcache_raw_supply (regcache, i, regs == NULL ? NULL : zero);
+	    }
 	  else
-	    p = regs;
-
-	  for (i = I387_XMM0_REGNUM (tdep);
-	       i < I387_MXCSR_REGNUM (tdep); i++)
 	    {
-	      if (p != NULL)
-		p = FXSAVE_ADDR (tdep, regs, i);
-	      regcache_raw_supply (regcache, i, p);
+	      for (i = I387_XMM0_REGNUM (tdep);
+		   i < I387_MXCSR_REGNUM (tdep); i++)
+		regcache_raw_supply (regcache, i,
+				     FXSAVE_ADDR (tdep, regs, i));
 	    }
 	}
 
@@ -886,16 +905,18 @@ i387_supply_xsave (struct regcache *regcache, int regnum,
       if ((tdep->xcr0 & I386_XSTATE_X87))
 	{
 	  if ((clear_bv & I386_XSTATE_X87))
-	    p = NULL;
+	    {
+	      for (i = I387_ST0_REGNUM (tdep);
+		   i < I387_FCTRL_REGNUM (tdep);
+		   i++)
+		regcache_raw_supply (regcache, i, regs == NULL ? NULL : zero);
+	    }
 	  else
-	    p = regs;
-
-	  for (i = I387_ST0_REGNUM (tdep);
-	       i < I387_FCTRL_REGNUM (tdep); i++)
 	    {
-	      if (p != NULL)
-		p = FXSAVE_ADDR (tdep, regs, i);
-	      regcache_raw_supply (regcache, i, p);
+	      for (i = I387_ST0_REGNUM (tdep);
+		   i < I387_FCTRL_REGNUM (tdep);
+		   i++)
+		regcache_raw_supply (regcache, i, FXSAVE_ADDR (tdep, regs, i));
 	    }
 	}
       break;