Re: [PATCH v2 11/16] perf annotate-arm64: Support stack variable tracking

[Namhyung Kim]

On Fri, Apr 03, 2026 at 09:47:55AM +0000, Tengda Wu wrote:
> Extend update_insn_state() for arm64 to track data types stored on the
> stack. This allows 'perf annotate' to maintain type information for
> local variables that are spilled to or loaded from stack slots.
> 
> The implementation handles:
> 1. Stack Loads (LDR): Identify when a register is loaded from a stack
>    slot and update the register's type state based on the tracked
>    stack content or compound member types.
> 2. Stack Stores (STR): Update or create new stack state entries when
>    a tracked register type is stored to the stack.
> 
> This enables the instruction tracker to follow data types as they move
> between registers and memory, specifically for function local variables
> and compiler-spilled values on arm64.
> 
> Signed-off-by: Tengda Wu <wutengda@xxxxxxxxxxxxxxx>
> ---
>  .../perf/util/annotate-arch/annotate-arm64.c  | 83 ++++++++++++++++++-
>  1 file changed, 80 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/annotate-arch/annotate-arm64.c b/tools/perf/util/annotate-arch/annotate-arm64.c
> index 28647a778802..f9100230c2f6 100644
> --- a/tools/perf/util/annotate-arch/annotate-arm64.c
> +++ b/tools/perf/util/annotate-arch/annotate-arm64.c
> @@ -11,6 +11,8 @@
>  #include "../disasm.h"
>  #include "../annotate-data.h"
>  #include "../debug.h"
> +#include "../map.h"
> +#include "../symbol.h"
>  
>  struct arch_arm64 {
>  	struct arch arch;
> @@ -297,6 +299,8 @@ static void update_insn_state_arm64(struct type_state *state,
>  	Dwarf_Die type_die;
>  	u32 insn_offset = dl->al.offset;
>  	int sreg, dreg;
> +	int fbreg = dloc->fbreg;
> +	int fboff = 0;
>  
>  	if (annotate_get_insn_location(dloc->arch, dl, &loc) < 0)
>  		return;
> @@ -304,17 +308,59 @@ static void update_insn_state_arm64(struct type_state *state,
>  	sreg = src->reg1;
>  	dreg = dst->reg1;
>  
> +	if (dloc->fb_cfa) {
> +		u64 ip = dloc->ms->sym->start + dl->al.offset;
> +		u64 pc = map__rip_2objdump(dloc->ms->map, ip);
> +
> +		if (die_get_cfa(dloc->di->dbg, pc, &fbreg, &fboff) < 0)
> +			fbreg = -1;
> +	}
> +
>  	/* Memory to register transfers */
>  	if (!strncmp(dl->ins.name, "ld", 2)) {
>  		struct type_state_reg dst_tsr;
>  
> -		if (!has_reg_type(state, sreg) ||
> -		    !has_reg_type(state, dreg) ||
> -		    !state->regs[dreg].ok)
> +		if (!has_reg_type(state, sreg))
>  			return;
>  
>  		tsr = &state->regs[sreg];
>  		tsr->copied_from = -1;
> +
> +		/* Check stack variables with offset */
> +		if (sreg == fbreg || sreg == state->stack_reg) {
> +			struct type_state_stack *stack;
> +			int offset = src->offset - fboff;
> +
> +			stack = find_stack_state(state, offset);
> +			if (stack == NULL) {
> +				tsr->ok = false;
> +				return;
> +			} else if (!stack->compound) {
> +				tsr->type = stack->type;
> +				tsr->kind = stack->kind;
> +				tsr->offset = stack->ptr_offset;
> +				tsr->ok = true;
> +			} else if (die_get_member_type(&stack->type,
> +						       offset - stack->offset,
> +						       &type_die)) {
> +				tsr->type = type_die;
> +				tsr->kind = TSR_KIND_TYPE;
> +				tsr->offset = 0;
> +				tsr->ok = true;
> +			} else {
> +				tsr->ok = false;
> +				return;
> +			}
> +
> +			pr_debug_dtp("ldr [%x] -%#x(stack) -> reg%d",
> +				     insn_offset, -offset, sreg);
> +			pr_debug_type_name(&tsr->type, tsr->kind);
> +			return;

Any chance the stack register changes the offset with the addressing
mode?  I think it should be updated regardless of the result of this
operation.

> +		}
> +
> +		if (!has_reg_type(state, dreg) || !state->regs[dreg].ok)
> +			return;
> +
>  		dst_tsr = state->regs[dreg];
>  
>  		/* Dereference the pointer if it has one */
> @@ -338,6 +384,37 @@ static void update_insn_state_arm64(struct type_state *state,
>  
>  	/* Register to memory transfers */
>  	if (!strncmp(dl->ins.name, "st", 2)) {
> +		/* Check stack variables with offset */
> +		if (dreg == fbreg || dreg == state->stack_reg) {
> +			struct type_state_stack *stack;
> +			int offset = dst->offset - fboff;
> +
> +			if (!has_reg_type(state, sreg) ||
> +			    !state->regs[sreg].ok)
> +				return;
> +
> +			tsr = &state->regs[sreg];
> +
> +			stack = find_stack_state(state, offset);
> +			if (stack) {
> +				if (!stack->compound)
> +					set_stack_state(stack, offset, tsr->kind,
> +							&tsr->type, tsr->offset);
> +			} else {
> +				findnew_stack_state(state, offset, tsr->kind,
> +						    &tsr->type, tsr->offset);
> +			}
> +
> +			pr_debug_dtp("str [%x] reg%d -> -%#x(stack)",
> +				     insn_offset, sreg, -offset);
> +			if (tsr->offset != 0) {
> +				pr_debug_dtp(" reg%d offset %#x ->",
> +					     sreg, tsr->offset);
> +			}
> +			pr_debug_type_name(&tsr->type, tsr->kind);
> +			return;

Ditto.

Thanks,
Namhyung


> +		}
> +
>  		/*
>  		 * Store instructions do not change the register type,
>  		 * but the base register must be updated for pre/post-index
> -- 
> 2.34.1
>