gdb/arm: Use new dwarf2 function cache

This patch resolves the performance issue reported in pr/29738 by
caching the values for the stack pointers for the inner frame.  By
doing so, the impact can be reduced to checking the state and
returning the appropriate value.

Signed-off-by: Torbjörn SVENSSON <[email protected]>
Signed-off-by: Yvan Roux <[email protected]>

Author: Torbjorn-Svensson

gdb/arm-tdep.c

@@ -3965,6 +3965,18 @@ struct frame_base arm_normal_base = {
   arm_normal_frame_base
 };
 
+struct arm_dwarf2_prev_register_cache
+{
+  /* Cached value of the coresponding stack pointer for the inner frame.  */
+  CORE_ADDR sp;
+  CORE_ADDR msp;
+  CORE_ADDR msp_s;
+  CORE_ADDR msp_ns;
+  CORE_ADDR psp;
+  CORE_ADDR psp_s;
+  CORE_ADDR psp_ns;
+};
+
 static struct value *
 arm_dwarf2_prev_register (frame_info_ptr this_frame, void **this_cache,
 			  int regnum)
@@ -3973,6 +3985,49 @@ arm_dwarf2_prev_register (frame_info_ptr this_frame, void **this_cache,
   arm_gdbarch_tdep *tdep = gdbarch_tdep<arm_gdbarch_tdep> (gdbarch);
   CORE_ADDR lr;
   ULONGEST cpsr;
+  arm_dwarf2_prev_register_cache *cache
+    = ((arm_dwarf2_prev_register_cache *)
+       dwarf2_frame_get_fn_data (this_frame, this_cache,
+				 arm_dwarf2_prev_register));
+
+  if (!cache)
+    {
+      const unsigned int size = sizeof (struct arm_dwarf2_prev_register_cache);
+      cache = ((arm_dwarf2_prev_register_cache *)
+	       dwarf2_frame_allocate_fn_data (this_frame, this_cache,
+					      arm_dwarf2_prev_register, size));
+
+      if (tdep->have_sec_ext)
+	{
+	  cache->sp
+	    = get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
+
+	  cache->msp_s
+	    = get_frame_register_unsigned (this_frame,
+					   tdep->m_profile_msp_s_regnum);
+	  cache->msp_ns
+	    = get_frame_register_unsigned (this_frame,
+					   tdep->m_profile_msp_ns_regnum);
+	  cache->psp_s
+	    = get_frame_register_unsigned (this_frame,
+					   tdep->m_profile_psp_s_regnum);
+	  cache->psp_ns
+	    = get_frame_register_unsigned (this_frame,
+					   tdep->m_profile_psp_ns_regnum);
+	}
+      else if (tdep->is_m)
+	{
+	  cache->sp
+	    = get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
+
+	  cache->msp
+	    = get_frame_register_unsigned (this_frame,
+					   tdep->m_profile_msp_regnum);
+	  cache->psp
+	    = get_frame_register_unsigned (this_frame,
+					   tdep->m_profile_psp_regnum);
+	}
+    }
 
   if (regnum == ARM_PC_REGNUM)
     {
@@ -4012,51 +4067,29 @@ arm_dwarf2_prev_register (frame_info_ptr this_frame, void **this_cache,
 
       if (tdep->have_sec_ext)
 	{
-	  CORE_ADDR sp
-	    = get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
-	  CORE_ADDR msp_s
-	    = get_frame_register_unsigned (this_frame,
-					   tdep->m_profile_msp_s_regnum);
-	  CORE_ADDR msp_ns
-	    = get_frame_register_unsigned (this_frame,
-					   tdep->m_profile_msp_ns_regnum);
-	  CORE_ADDR psp_s
-	    = get_frame_register_unsigned (this_frame,
-					   tdep->m_profile_psp_s_regnum);
-	  CORE_ADDR psp_ns
-	    = get_frame_register_unsigned (this_frame,
-					   tdep->m_profile_psp_ns_regnum);
-
 	  bool is_msp = (regnum == tdep->m_profile_msp_regnum)
-	    && (msp_s == sp || msp_ns == sp);
+	    && (cache->msp_s == cache->sp || cache->msp_ns == cache->sp);
 	  bool is_msp_s = (regnum == tdep->m_profile_msp_s_regnum)
-	    && (msp_s == sp);
+	    && (cache->msp_s == cache->sp);
 	  bool is_msp_ns = (regnum == tdep->m_profile_msp_ns_regnum)
-	    && (msp_ns == sp);
+	    && (cache->msp_ns == cache->sp);
 	  bool is_psp = (regnum == tdep->m_profile_psp_regnum)
-	    && (psp_s == sp || psp_ns == sp);
+	    && (cache->psp_s == cache->sp || cache->psp_ns == cache->sp);
 	  bool is_psp_s = (regnum == tdep->m_profile_psp_s_regnum)
-	    && (psp_s == sp);
+	    && (cache->psp_s == cache->sp);
 	  bool is_psp_ns = (regnum == tdep->m_profile_psp_ns_regnum)
-	    && (psp_ns == sp);
+	    && (cache->psp_ns == cache->sp);
 
 	  override_with_sp_value = is_msp || is_msp_s || is_msp_ns
 	    || is_psp || is_psp_s || is_psp_ns;
 
 	}
       else if (tdep->is_m)
 	{
-	  CORE_ADDR sp
-	    = get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
-	  CORE_ADDR msp
-	    = get_frame_register_unsigned (this_frame,
-					   tdep->m_profile_msp_regnum);
-	  CORE_ADDR psp
-	    = get_frame_register_unsigned (this_frame,
-					   tdep->m_profile_psp_regnum);
-
-	  bool is_msp = (regnum == tdep->m_profile_msp_regnum) && (sp == msp);
-	  bool is_psp = (regnum == tdep->m_profile_psp_regnum) && (sp == psp);
+	  bool is_msp = (regnum == tdep->m_profile_msp_regnum)
+	    && (cache->sp == cache->msp);
+	  bool is_psp = (regnum == tdep->m_profile_psp_regnum)
+	    && (cache->sp == cache->psp);
 
 	  override_with_sp_value = is_msp || is_psp;
 	}