perf dwarf-aux: Skip check_variable for variable lookup

Both die_find_variable_by_reg and die_find_variable_by_addr call
match_var_offset which already performs sufficient checking and type
matching. The additional check_variable call is redundant, and its
need_pointer logic is only a heuristic. Since DWARF encodes accurate
type information, which match_var_offset verifies, skipping
check_variable improves both coverage and accuracy.

Return the matched type from die_find_variable_by_reg and
die_find_variable_by_addr via the existing `type` field in
find_var_data, removing the need for check_variable in
find_data_type_die.

Signed-off-by: Zecheng Li <zecheng@google.com>
Signed-off-by: Zecheng Li <zli94@ncsu.edu>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

3 files changed, 30 insertions, 30 deletions

diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
index cda020ea18d5..23a09bf58f86 100644
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -814,9 +814,8 @@ bool get_global_var_type(Dwarf_Die *cu_die, struct data_loc_info *dloc,
 	}
 
 	/* Try to get the variable by address first */
-	if (die_find_variable_by_addr(cu_die, var_addr, &var_die, &offset) &&
-	    check_variable(dloc, &var_die, type_die, DWARF_REG_PC, offset,
-			   /*is_fbreg=*/false) == PERF_TMR_OK) {
+	if (die_find_variable_by_addr(cu_die, var_addr, &var_die, type_die,
+				      &offset)) {
 		var_name = dwarf_diename(&var_die);
 		*var_offset = offset;
 		goto ok;
@@ -1606,12 +1605,13 @@ retry:
 
 		if (reg == DWARF_REG_PC) {
 			if (!die_find_variable_by_addr(&scopes[i], dloc->var_addr,
-						       &var_die, &type_offset))
+						       &var_die, &mem_die,
+						       &type_offset))
 				continue;
 		} else {
 			/* Look up variables/parameters in this scope */
 			if (!die_find_variable_by_reg(&scopes[i], pc, reg,
-						      &type_offset, is_fbreg, &var_die))
+						      &mem_die, &type_offset, is_fbreg, &var_die))
 				continue;
 		}
 
@@ -1619,26 +1619,20 @@ retry:
 			     dwarf_diename(&var_die), (long)dwarf_dieoffset(&var_die),
 			     i+1, nr_scopes, (long)dwarf_dieoffset(&scopes[i]));
 
-		/* Found a variable, see if it's correct */
-		result = check_variable(dloc, &var_die, &mem_die, reg, type_offset, is_fbreg);
-		if (result == PERF_TMR_OK) {
-			if (reg == DWARF_REG_PC) {
-				pr_debug_dtp("addr=%#"PRIx64" type_offset=%#x\n",
-					     dloc->var_addr, type_offset);
-			} else if (reg == DWARF_REG_FB || is_fbreg) {
-				pr_debug_dtp("stack_offset=%#x type_offset=%#x\n",
-					     fb_offset, type_offset);
-			} else {
-				pr_debug_dtp("type_offset=%#x\n", type_offset);
-			}
-
-			if (!found || is_better_type(type_die, &mem_die)) {
-				*type_die = mem_die;
-				dloc->type_offset = type_offset;
-				found = true;
-			}
+		if (reg == DWARF_REG_PC) {
+			pr_debug_dtp("addr=%#"PRIx64" type_offset=%#x\n",
+				     dloc->var_addr, type_offset);
+		} else if (reg == DWARF_REG_FB || is_fbreg) {
+			pr_debug_dtp("stack_offset=%#x type_offset=%#x\n",
+				     fb_offset, type_offset);
 		} else {
-			pr_debug_dtp("failed: %s\n", match_result_str(result));
+			pr_debug_dtp("type_offset=%#x\n", type_offset);
+		}
+
+		if (!found || is_better_type(type_die, &mem_die)) {
+			*type_die = mem_die;
+			dloc->type_offset = type_offset;
+			found = true;
 		}
 
 		pr_debug_location(&var_die, pc, reg);
diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index 3b0fc9038f19..1484aa756826 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -1560,7 +1560,7 @@ static int __die_find_var_reg_cb(Dwarf_Die *die_mem, void *arg)
  * when the variable is in the stack.
  */
 Dwarf_Die *die_find_variable_by_reg(Dwarf_Die *sc_die, Dwarf_Addr pc, int reg,
-				    int *poffset, bool is_fbreg,
+				    Dwarf_Die *type_die, int *poffset, bool is_fbreg,
 				    Dwarf_Die *die_mem)
 {
 	struct find_var_data data = {
@@ -1572,8 +1572,10 @@ Dwarf_Die *die_find_variable_by_reg(Dwarf_Die *sc_die, Dwarf_Addr pc, int reg,
 	Dwarf_Die *result;
 
 	result = die_find_child(sc_die, __die_find_var_reg_cb, &data, die_mem);
-	if (result)
+	if (result) {
 		*poffset = data.offset;
+		*type_die = data.type;
+	}
 	return result;
 }
 
@@ -1617,7 +1619,8 @@ static int __die_find_var_addr_cb(Dwarf_Die *die_mem, void *arg)
  * This is usually for global variables.
  */
 Dwarf_Die *die_find_variable_by_addr(Dwarf_Die *sc_die, Dwarf_Addr addr,
-				     Dwarf_Die *die_mem, int *offset)
+				     Dwarf_Die *die_mem, Dwarf_Die *type_die,
+				     int *offset)
 {
 	struct find_var_data data = {
 		.addr = addr,
@@ -1625,8 +1628,10 @@ Dwarf_Die *die_find_variable_by_addr(Dwarf_Die *sc_die, Dwarf_Addr addr,
 	Dwarf_Die *result;
 
 	result = die_find_child(sc_die, __die_find_var_addr_cb, &data, die_mem);
-	if (result)
+	if (result) {
 		*offset = data.offset;
+		*type_die = data.type;
+	}
 	return result;
 }
 
diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h
index 99d2735122d5..939a59c91796 100644
--- a/tools/perf/util/dwarf-aux.h
+++ b/tools/perf/util/dwarf-aux.h
@@ -165,12 +165,13 @@ int die_get_var_range(Dwarf_Die *sp_die, Dwarf_Die *vr_die, struct strbuf *buf);
 
 /* Find a variable saved in the 'reg' at given address */
 Dwarf_Die *die_find_variable_by_reg(Dwarf_Die *sc_die, Dwarf_Addr pc, int reg,
-				    int *poffset, bool is_fbreg,
+				    Dwarf_Die *type_die, int *poffset, bool is_fbreg,
 				    Dwarf_Die *die_mem);
 
 /* Find a (global) variable located in the 'addr' */
 Dwarf_Die *die_find_variable_by_addr(Dwarf_Die *sc_die, Dwarf_Addr addr,
-				     Dwarf_Die *die_mem, int *offset);
+				     Dwarf_Die *die_mem, Dwarf_Die *type_die,
+				     int *offset);
 
 /* Save all variables and parameters in this scope */
 void die_collect_vars(Dwarf_Die *sc_die, struct die_var_type **var_types);