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Add support for metadata.code.call_targets section #4664

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ed551fe
Add support for metadata.code.call_targets section
Lukasdoe Aug 24, 2025
4500f7b
formatting
Lukasdoe Oct 15, 2025
a426b7d
remove non-const array initializer
Lukasdoe Oct 15, 2025
1474a8d
msvc fix: error C2036: 'void *': unknown size
Lukasdoe Oct 15, 2025
163b8ad
fixes for review
Lukasdoe Nov 28, 2025
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1 change: 1 addition & 0 deletions build-scripts/config_common.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -778,6 +778,7 @@ message (
" \"Sign-extension Operators\"\n"
" \"WebAssembly C and C++ API\"\n"
" \"Branch Hinting\"\n"
" \"Compilation Hints\"\n"
" Configurable. 0 is OFF. 1 is ON:\n"
" \"Bulk Memory Operation\" via WAMR_BUILD_BULK_MEMORY: ${WAMR_BUILD_BULK_MEMORY}\n"
" \"Bulk-memory-opt\" via WAMR_BUILD_BULK_MEMORY_OPT: ${WAMR_BUILD_BULK_MEMORY_OPT}\n"
Expand Down
4 changes: 4 additions & 0 deletions core/config.h
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Expand Up @@ -591,6 +591,10 @@ unless used elsewhere */
#define WASM_ENABLE_BRANCH_HINTS 0
#endif

#ifndef WASM_ENABLE_COMPILATION_HINTS
#define WASM_ENABLE_COMPILATION_HINTS 0
#endif

#ifndef WASM_ENABLE_GC
#define WASM_ENABLE_GC 0
#endif
Expand Down
4 changes: 2 additions & 2 deletions core/iwasm/compilation/aot.c
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Expand Up @@ -416,7 +416,7 @@ aot_create_funcs(const WASMModule *module, uint32 pointer_size)
aot_func->local_types_wp = func->local_types;
aot_func->code = func->code;
aot_func->code_size = func->code_size;
#if WASM_ENABLE_BRANCH_HINTS != 0
#if WASM_ENABLE_BRANCH_HINTS != 0 || WASM_ENABLE_COMPILATION_HINTS != 0
aot_func->code_body_begin = func->code_body_begin;
#endif

Expand Down Expand Up @@ -875,7 +875,7 @@ aot_create_comp_data(WASMModule *module, const char *target_arch,
comp_data->name_section_buf_end = module->name_section_buf_end;
#endif

#if WASM_ENABLE_BRANCH_HINTS != 0
#if WASM_ENABLE_BRANCH_HINTS != 0 || WASM_ENABLE_COMPILATION_HINTS != 0
comp_data->function_hints = module->function_hints;
#endif

Expand Down
4 changes: 2 additions & 2 deletions core/iwasm/compilation/aot.h
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Expand Up @@ -217,7 +217,7 @@ typedef struct AOTFunc {
/* offset of each local, including function parameters
and local variables */
uint16 *local_offsets;
#if WASM_ENABLE_BRANCH_HINTS != 0
#if WASM_ENABLE_BRANCH_HINTS != 0 || WASM_ENABLE_COMPILATION_HINTS != 0
uint8 *code_body_begin;
#endif
} AOTFunc;
Expand Down Expand Up @@ -300,7 +300,7 @@ typedef struct AOTCompData {
dwarf_extractor_handle_t extractor;
#endif

#if WASM_ENABLE_BRANCH_HINTS != 0
#if WASM_ENABLE_BRANCH_HINTS != 0 || WASM_ENABLE_COMPILATION_HINTS != 0
struct WASMCompilationHint **function_hints;
#endif
} AOTCompData;
Expand Down
16 changes: 14 additions & 2 deletions core/iwasm/compilation/aot_compiler.c
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Expand Up @@ -1233,6 +1233,12 @@ aot_compile_func(AOTCompContext *comp_ctx, uint32 func_index)

case WASM_OP_CALL_INDIRECT:
{
#if WASM_ENABLE_COMPILATION_HINTS != 0
const uint32 instr_offset =
(frame_ip - 0x1) - (func_ctx->aot_func->code_body_begin);
#else
const uint32 instr_offset = 0;
#endif
uint32 tbl_idx;

read_leb_uint32(frame_ip, frame_ip_end, type_idx);
Expand All @@ -1246,7 +1252,7 @@ aot_compile_func(AOTCompContext *comp_ctx, uint32 func_index)
}

if (!aot_compile_op_call_indirect(comp_ctx, func_ctx, type_idx,
tbl_idx))
tbl_idx, instr_offset))
return false;
break;
}
Expand All @@ -1269,6 +1275,12 @@ aot_compile_func(AOTCompContext *comp_ctx, uint32 func_index)

case WASM_OP_RETURN_CALL_INDIRECT:
{
#if WASM_ENABLE_COMPILATION_HINTS != 0
const uint32 instr_offset =
(frame_ip - 0x1) - (func_ctx->aot_func->code_body_begin);
#else
const uint32 instr_offset = 0;
#endif
uint32 tbl_idx;

if (!comp_ctx->enable_tail_call) {
Expand All @@ -1286,7 +1298,7 @@ aot_compile_func(AOTCompContext *comp_ctx, uint32 func_index)
}

if (!aot_compile_op_call_indirect(comp_ctx, func_ctx, type_idx,
tbl_idx))
tbl_idx, instr_offset))
return false;
if (!aot_compile_op_return(comp_ctx, func_ctx, &frame_ip))
return false;
Expand Down
12 changes: 6 additions & 6 deletions core/iwasm/compilation/aot_emit_control.c
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Expand Up @@ -272,14 +272,14 @@ aot_emit_branch_hint(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,
{
struct WASMCompilationHint *hint = func_ctx->function_hints;
while (hint != NULL) {
if (hint->type == WASM_COMPILATION_BRANCH_HINT
&& ((struct WASMCompilationHintBranchHint *)hint)->offset
== offset) {
if (hint->type == WASM_COMPILATION_HINT_BRANCH
&& hint->offset == offset) {
break;
}
hint = hint->next;
}
if (hint != NULL) {
hint->used = true;
// same weight llvm MDBuilder::createLikelyBranchWeights assigns
const uint32_t likely_weight = (1U << 20) - 1;
const uint32_t unlikely_weight = 1;
Expand Down Expand Up @@ -1094,11 +1094,11 @@ aot_compile_conditional_br(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,
uint64 size;

// ip is advanced by one byte for the opcode
#if WASM_ENABLE_BRANCH_HINTS != 0
uint32 instr_offset =
#if WASM_ENABLE_BRANCH_HINTS != 0 || WASM_ENABLE_COMPILATION_HINTS != 0
const uint32 instr_offset =
(*p_frame_ip - 0x1) - (func_ctx->aot_func->code_body_begin);
#else
uint32 instr_offset = 0;
const uint32 instr_offset = 0;
#endif
uint64 br_depth;
if (!read_leb(p_frame_ip, *p_frame_ip + 5, 32, false, &br_depth, NULL, 0))
Expand Down
70 changes: 66 additions & 4 deletions core/iwasm/compilation/aot_emit_function.c
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Expand Up @@ -112,6 +112,64 @@ check_exception_thrown(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx)
return true;
}

#if WASM_ENABLE_COMPILATION_HINTS != 0
static void
aot_emit_call_target_hint(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,
uint32 offset, LLVMValueRef call_instr)
{
struct WASMCompilationHint *hint = func_ctx->function_hints;
while (hint != NULL) {
if (hint->type == WASM_COMPILATION_HINT_CALL_TARGETS
&& hint->offset == offset) {
break;
}
hint = hint->next;
}
if (hint != NULL) {
hint->used = true;
struct WASMCompilationHintCallTargets *ct_hint =
(struct WASMCompilationHintCallTargets *)hint;

const unsigned md_node_cnt = ct_hint->target_count * 2 + 3;
LLVMMetadataRef *md_nodes =
wasm_runtime_malloc(md_node_cnt * sizeof(LLVMMetadataRef));
if (!md_nodes) {
aot_set_last_error("allocate memory failed.");
return;
}

md_nodes[0] =
LLVMMDStringInContext2(comp_ctx->context, "VP", strlen("VP"));
md_nodes[1] = LLVMValueAsMetadata(I32_CONST(0));
// since wasm encodes a call frequency in full percent, we forward this
// to llvm as 100 calls to match the percentages
// (could be enhanced with the instruction frequency hints)
md_nodes[2] = LLVMValueAsMetadata(I64_CONST(100));

for (size_t i = 0; i < ct_hint->target_count; ++i) {
struct WASMCompilationHintCallTargetsHint *target =
&ct_hint->hints[i];
char target_func_name[48];
snprintf(target_func_name, sizeof(target_func_name), "%s%d",
AOT_FUNC_PREFIX,
target->func_idx - comp_ctx->comp_data->import_func_count);
const uint64_t func_name_hash =
aot_func_name_hash(target_func_name);
md_nodes[i * 2 + 3] =
LLVMValueAsMetadata(I64_CONST(func_name_hash));
md_nodes[i * 2 + 3 + 1] =
LLVMValueAsMetadata(I64_CONST(target->call_frequency));
}
LLVMMetadataRef meta_data =
LLVMMDNodeInContext2(comp_ctx->context, md_nodes, md_node_cnt);
LLVMValueRef meta_data_as_value =
LLVMMetadataAsValue(comp_ctx->context, meta_data);
LLVMSetMetadata(call_instr, 2, meta_data_as_value);
wasm_runtime_free(md_nodes);
}
}
#endif

/* Check whether there was exception thrown, if yes, return directly */
static bool
check_call_return(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,
Expand Down Expand Up @@ -1929,7 +1987,7 @@ call_aot_call_indirect_func(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,
LLVMValueRef *param_values, uint32 param_count,
uint32 param_cell_num, uint32 result_count,
uint8 *wasm_ret_types, LLVMValueRef *value_rets,
LLVMValueRef *p_res)
LLVMValueRef *p_res, uint32 instr_offset)
{
LLVMTypeRef func_type, func_ptr_type, func_param_types[6];
LLVMTypeRef ret_type, ret_ptr_type, elem_ptr_type;
Expand Down Expand Up @@ -2074,14 +2132,14 @@ call_aot_call_indirect_func(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,
cell_num += wasm_value_type_cell_num_internal(wasm_ret_types[i],
comp_ctx->pointer_size);
}

*p_res = res;
return true;
}

bool
aot_compile_op_call_indirect(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,
uint32 type_idx, uint32 tbl_idx)
uint32 type_idx, uint32 tbl_idx,
uint32 instr_offset)
{
AOTFuncType *func_type;
LLVMValueRef tbl_idx_value, elem_idx, func_idx;
Expand Down Expand Up @@ -2620,7 +2678,7 @@ aot_compile_op_call_indirect(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,
if (!call_aot_call_indirect_func(
comp_ctx, func_ctx, func_type, ftype_idx, tbl_idx_value, elem_idx,
param_types + 1, param_values + 1, func_param_count, param_cell_num,
func_result_count, wasm_ret_types, value_rets, &res))
func_result_count, wasm_ret_types, value_rets, &res, instr_offset))
goto fail;

/* Check whether exception was thrown when executing the function */
Expand Down Expand Up @@ -2681,6 +2739,10 @@ aot_compile_op_call_indirect(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,
goto fail;
}

#if WASM_ENABLE_COMPILATION_HINTS != 0
aot_emit_call_target_hint(comp_ctx, func_ctx, instr_offset, value_ret);
#endif

/* Check whether exception was thrown when executing the function */
if ((comp_ctx->enable_bound_check || is_win_platform(comp_ctx))
&& !check_exception_thrown(comp_ctx, func_ctx))
Expand Down
3 changes: 2 additions & 1 deletion core/iwasm/compilation/aot_emit_function.h
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Expand Up @@ -18,7 +18,8 @@ aot_compile_op_call(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,

bool
aot_compile_op_call_indirect(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,
uint32 type_idx, uint32 tbl_idx);
uint32 type_idx, uint32 tbl_idx,
uint32 instr_offset);

bool
aot_compile_op_ref_null(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx);
Expand Down
2 changes: 1 addition & 1 deletion core/iwasm/compilation/aot_llvm.c
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Expand Up @@ -1963,7 +1963,7 @@ aot_create_func_context(const AOTCompData *comp_data, AOTCompContext *comp_ctx,
goto fail;
}

#if WASM_ENABLE_BRANCH_HINTS != 0
#if WASM_ENABLE_BRANCH_HINTS != 0 || WASM_ENABLE_COMPILATION_HINTS != 0
func_ctx->function_hints =
comp_ctx->comp_data->function_hints
? comp_ctx->comp_data->function_hints[func_index]
Expand Down
5 changes: 4 additions & 1 deletion core/iwasm/compilation/aot_llvm.h
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Expand Up @@ -270,7 +270,7 @@ typedef struct AOTFuncContext {
#if WASM_ENABLE_DEBUG_AOT != 0
LLVMMetadataRef debug_func;
#endif
#if WASM_ENABLE_BRANCH_HINTS != 0
#if WASM_ENABLE_BRANCH_HINTS != 0 || WASM_ENABLE_COMPILATION_HINTS != 0
struct WASMCompilationHint *function_hints;
#endif

Expand Down Expand Up @@ -674,6 +674,9 @@ unsigned int
aot_estimate_stack_usage_for_function_call(const AOTCompContext *comp_ctx,
const AOTFuncType *callee_func_type);

uint64_t
aot_func_name_hash(const char *name);

#ifdef __cplusplus
} /* end of extern "C" */
#endif
Expand Down
6 changes: 6 additions & 0 deletions core/iwasm/compilation/aot_llvm_extra.cpp
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Expand Up @@ -433,3 +433,9 @@ aot_compress_aot_func_names(AOTCompContext *comp_ctx, uint32 *p_size)
*p_size = compressed_str_len;
return compressed_str;
}

uint64_t
aot_func_name_hash(const char *name)
{
return MD5Hash(StringRef(name));
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@yamt yamt Nov 4, 2025

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is this function ubiquitously available?
i suspect it isn't.

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@Lukasdoe Lukasdoe Nov 28, 2025

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Can you please elaborate a bit more on that? I don't understand what your concern is, since I'm not sure whether you are hinting at the availability of the MD5Hash function, which is part of LLVM's MD5.h support header, or something else.

}
24 changes: 17 additions & 7 deletions core/iwasm/interpreter/wasm.h
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Expand Up @@ -752,7 +752,7 @@ struct WASMFunction {
#endif
#endif

#if WASM_ENABLE_BRANCH_HINTS != 0
#if WASM_ENABLE_BRANCH_HINTS != 0 || WASM_ENABLE_COMPILATION_HINTS != 0
uint8 *code_body_begin;
#endif
};
Expand All @@ -765,21 +765,31 @@ struct WASMTag {
};
#endif

#if WASM_ENABLE_BRANCH_HINTS != 0
#if WASM_ENABLE_BRANCH_HINTS != 0 || WASM_ENABLE_COMPILATION_HINTS != 0
enum WASMCompilationHintType {
DUMMY = 0,
WASM_COMPILATION_BRANCH_HINT = 0,
WASM_COMPILATION_HINT_BRANCH = 1,
WASM_COMPILATION_HINT_CALL_TARGETS = 2,
};
struct WASMCompilationHint {
struct WASMCompilationHint *next;
enum WASMCompilationHintType type;
uint32 offset;
bool used;
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@yamt yamt Nov 4, 2025

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is this used field only for diagnostic purposes?

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@Lukasdoe Lukasdoe Nov 28, 2025

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more or less. It is definitely a hint that something is wrong if a hint is not used. We apply hints to all branch instructions, so if it is not used, we either missed it, or the referenced instruction does not exist (meaning an invalid compilation hint section).

However, since these hints are not mission-critical, I didn't want to assert that this is true.

};
struct WASMCompilationHintBranchHint {
struct WASMCompilationHint *next;
enum WASMCompilationHintType type;
uint32 offset;
struct WASMCompilationHint common;
bool is_likely;
};
struct WASMCompilationHintCallTargetsHint {
uint32 func_idx;
uint32 call_frequency;
};
struct WASMCompilationHintCallTargets {
struct WASMCompilationHint common;
size_t target_count;
struct WASMCompilationHintCallTargetsHint *hints;
};
#endif

struct WASMGlobal {
Expand Down Expand Up @@ -1070,7 +1080,7 @@ struct WASMModule {
const uint8 *name_section_buf_end;
#endif

#if WASM_ENABLE_BRANCH_HINTS != 0
#if WASM_ENABLE_BRANCH_HINTS != 0 || WASM_ENABLE_COMPILATION_HINTS != 0
struct WASMCompilationHint **function_hints;
#endif

Expand Down
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