[PATCH v5 14/26] perf annotate-data: Add arch_get_reg_offset helper

[Tengda Wu]

Add a helper to compute the effective offset from a base register
for instruction operands. Currently handles arm64 addressing modes
including post-indexed, single-register, SIB-style indexed with
shift/extension, and constant-offset register pairs.

Fallback to instruction's raw offset for other architectures.

Signed-off-by: Tengda Wu <wutengda@xxxxxxxxxxxxxxx>
---
 tools/perf/util/annotate-data.c | 106 +++++++++++++++++++++++++++-----
 tools/perf/util/annotate-data.h |   4 +-
 2 files changed, 94 insertions(+), 16 deletions(-)

diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
index c51b20a7af9b..754c0efe2077 100644
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -1118,6 +1118,74 @@ static void setup_stack_canary(struct data_loc_info *dloc)
 	}
 }
 
+int arch_get_reg_offset(const struct arch *arch, struct annotated_op_loc *op_loc,
+			int breg, struct type_state *state, bool apply_index,
+			int *offset)
+{
+	if (arch__is_arm64(arch)) {
+		int reg2;
+
+		/* Post-indexed addressing: offset is 0 when not applying index */
+		if (op_loc->addr_mode == PERF_AAM_POST_INDEX && !apply_index) {
+			*offset = 0;
+			return 0;
+		}
+
+		/* Single-register addressing: return the stored offset directly */
+		if (!op_loc->multi_regs) {
+			*offset = op_loc->offset;
+			return 0;
+		}
+
+		/*
+		 * SIB (Scale-Index-Base) style indexed addressing, e.g.:
+		 *   Array element load:  ldr  dst, [base, index, lsl #3]
+		 *   Array element load:  ldr  dst, [base, index, uxtw #3]
+		 *   Array address calc:  add  dst, base, index lsl #3
+		 *
+		 * The index reg only computes element offset without modifying
+		 * the underlying data type; the dst type is inherited from base.
+		 * Therefore, the base reg offset can be treated as 0.
+		 */
+		if (op_loc->extend_type || op_loc->shift_type) {
+			/* Memory references use the breg as the address base. */
+			if (op_loc->mem_ref) {
+				*offset = 0;
+				return 0;
+			}
+			/*
+			 * Otherwise, require breg to be a known pointer type to
+			 * avoid treating integer operations as address calculations.
+			 */
+			if (has_reg_type(state, breg) && state->regs[breg].ok &&
+			    (state->regs[breg].kind == TSR_KIND_POINTER ||
+			     (state->regs[breg].kind == TSR_KIND_TYPE &&
+			      dwarf_tag(&state->regs[breg].type) == DW_TAG_pointer_type))) {
+				*offset = 0;
+				return 0;
+			}
+			return -1;
+		}
+
+		/*
+		 * For register-based addressing without shift/extension,
+		 * reg2 may be a constant offset. Use its value as the offset
+		 * from the base register.
+		 */
+		reg2 = op_loc->reg1 == breg ? op_loc->reg2 : op_loc->reg1;
+		if (has_reg_type(state, reg2) && state->regs[reg2].ok &&
+			state->regs[reg2].kind == TSR_KIND_CONST) {
+			*offset = (s64)state->regs[reg2].imm_value;
+			return 0;
+		}
+
+		return -1;
+	}
+
+	*offset = op_loc->offset;
+	return 0;
+}
+
 /*
  * It's at the target address, check if it has a matching type.
  * It returns PERF_TMR_BAIL_OUT when it looks up per-cpu variables which
@@ -1132,18 +1200,26 @@ static enum type_match_result check_matching_type(struct type_state *state,
 	Dwarf_Word size;
 	u32 insn_offset = dl->al.offset;
 	int reg = dloc->op->reg1;
-	int offset = dloc->op->offset;
+	int offset;
 	const char *offset_sign = "";
 	bool retry = true;
 
-	if (offset < 0) {
-		offset = -offset;
-		offset_sign = "-";
+again:
+	if (arch_get_reg_offset(dloc->arch, dloc->op, reg, state, false, &offset)) {
+		/*
+		 * Fall back to the instruction's offset. This prevents the
+		 * register type of the instruction from being completely lost.
+		 * Compared to dropping this type inference entirely, providing
+		 * a rough type hint is likely more useful.
+		 */
+		offset = dloc->op->offset;
 	}
 
-again:
+	if (offset < 0)
+		offset_sign = "-";
+
 	pr_debug_dtp("chk [%x] reg%d offset=%s%#x ok=%d kind=%d ",
-		     insn_offset, reg, offset_sign, offset,
+		     insn_offset, reg, offset_sign, abs(offset),
 		     state->regs[reg].ok, state->regs[reg].kind);
 
 	if (!state->regs[reg].ok)
@@ -1166,7 +1242,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
 		 */
 		ptr_type = die_get_pointer_type(&state->regs[reg].type, &ptr_die);
 		if (!ptr_type) {
-			if (dloc->op->offset < 0 && reg != state->stack_reg)
+			if (offset < 0 && reg != state->stack_reg)
 				goto check_kernel;
 
 			return PERF_TMR_NO_POINTER;
@@ -1176,7 +1252,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
 		if (__die_get_real_type(ptr_type, type_die) == NULL)
 			return PERF_TMR_NO_POINTER;
 
-		dloc->type_offset = dloc->op->offset + state->regs[reg].offset;
+		dloc->type_offset = offset + state->regs[reg].offset;
 
 		if (dwarf_tag(type_die) == DW_TAG_typedef)
 			die_get_real_type(type_die, &sized_type);
@@ -1205,7 +1281,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
 		 */
 		*type_die = state->regs[reg].type;
 
-		dloc->type_offset = dloc->op->offset + state->regs[reg].offset;
+		dloc->type_offset = offset + state->regs[reg].offset;
 
 		/* Get the size of the actual type */
 		if (dwarf_aggregate_size(type_die, &size) < 0 ||
@@ -1224,7 +1300,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
 		 */
 		*type_die = state->regs[reg].type;
 
-		dloc->type_offset = dloc->op->offset;
+		dloc->type_offset = offset;
 
 		/* Get the size of the actual type */
 		if (dwarf_aggregate_size(type_die, &size) < 0 ||
@@ -1248,7 +1324,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
 	}
 
 	if (state->regs[reg].kind == TSR_KIND_PERCPU_BASE) {
-		u64 var_addr = dloc->op->offset;
+		u64 var_addr = (s64) offset;
 		int var_offset;
 
 		pr_debug_dtp("percpu var");
@@ -1275,7 +1351,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
 
 	if (state->regs[reg].kind == TSR_KIND_CONST &&
 	    dso__kernel(map__dso(dloc->ms->map))) {
-		if (dloc->op->offset < 0 && reg != state->stack_reg && reg != dloc->fbreg)
+		if (offset < 0 && reg != state->stack_reg && reg != dloc->fbreg)
 			goto check_kernel;
 	}
 check_non_register:
@@ -1362,7 +1438,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
 		    arch__is_x86(dloc->arch)) {
 			pr_debug_dtp("this-cpu var");
 
-			addr = dloc->op->offset;
+			addr = (s64) offset;
 
 			if (get_global_var_type(cu_die, dloc, dloc->ip, addr,
 						&offset, type_die)) {
@@ -1373,8 +1449,8 @@ static enum type_match_result check_matching_type(struct type_state *state,
 		}
 
 		/* Access to global variable like "-0x7dcf0500(,%rdx,8)" */
-		if (dloc->op->offset < 0 && reg != state->stack_reg) {
-			addr = (s64) dloc->op->offset;
+		if (offset < 0 && reg != state->stack_reg) {
+			addr = (s64) offset;
 
 			if (get_global_var_type(cu_die, dloc, dloc->ip, addr,
 						&offset, type_die)) {
diff --git a/tools/perf/util/annotate-data.h b/tools/perf/util/annotate-data.h
index 453e13bbe3e2..e6ca47e25e04 100644
--- a/tools/perf/util/annotate-data.h
+++ b/tools/perf/util/annotate-data.h
@@ -265,7 +265,9 @@ bool get_global_var_type(Dwarf_Die *cu_die, struct data_loc_info *dloc,
 bool get_global_var_info(struct data_loc_info *dloc, u64 addr,
 				const char **var_name, int *var_offset);
 void pr_debug_type_name(Dwarf_Die *die, enum type_state_kind kind);
-
+int arch_get_reg_offset(const struct arch *arch, struct annotated_op_loc *op_loc,
+			int breg, struct type_state *state, bool apply_index,
+			int *offset);
 #else /* HAVE_LIBDW_SUPPORT */
 
 static inline struct annotated_data_type *
-- 
2.34.1