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Optimize memory bounds checks on narrow targets #13

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Merged
espmaniac merged 1 commit into from
Aug 12, 2026
Merged

Optimize memory bounds checks on narrow targets #13

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40 changes: 28 additions & 12 deletions source/m3_exec.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1537,18 +1537,34 @@ d_m3Op (SetGlobal_f64)
# define m3MemCheck(x) M3_LIKELY(x)
#endif

// WebAssembly memory32 addresses and memory instruction offsets are unsigned
// 32-bit values. Native 64-bit targets can check their sum directly. On
// narrower targets, EFFECTIVE >= OFFSET detects 32-bit addition wraparound;
// subtracting the access size from the memory length is guarded separately.
#if M3_SIZEOF_PTR >= 8
typedef u64 m3_mem_addr_t;
# define m3MemAccessInBounds(EFFECTIVE, OFFSET, ACCESS_SIZE, MEMORY_LENGTH) \
((EFFECTIVE) + (ACCESS_SIZE) <= (MEMORY_LENGTH))
#else
typedef u32 m3_mem_addr_t;
# define m3MemAccessInBounds(EFFECTIVE, OFFSET, ACCESS_SIZE, MEMORY_LENGTH) \
((EFFECTIVE) >= (OFFSET) \
&& (ACCESS_SIZE) <= (MEMORY_LENGTH) \
&& (EFFECTIVE) <= (MEMORY_LENGTH) - (ACCESS_SIZE))
#endif

// memcpy here is to support non-aligned access on some platforms.

#define d_m3Load(REG,DEST_TYPE,SRC_TYPE) \
d_m3Op(DEST_TYPE##_Load_##SRC_TYPE##_r) \
{ \
d_m3TracePrepare \
u32 offset = immediate (u32); \
u64 operand = (u32) _r0; \
m3_mem_addr_t operand = (u32) _r0; \
operand += offset; \
\
if (m3MemCheck( \
operand + sizeof (SRC_TYPE) <= _mem->length \
m3MemAccessInBounds (operand, offset, sizeof (SRC_TYPE), _mem->length) \
)) { \
{ \
u8* src8 = m3MemData(_mem) + operand; \
Expand All @@ -1564,12 +1580,12 @@ d_m3Op(DEST_TYPE##_Load_##SRC_TYPE##_r) \
d_m3Op(DEST_TYPE##_Load_##SRC_TYPE##_s) \
{ \
d_m3TracePrepare \
u64 operand = slot (u32); \
m3_mem_addr_t operand = slot (u32); \
u32 offset = immediate (u32); \
operand += offset; \
\
if (m3MemCheck( \
operand + sizeof (SRC_TYPE) <= _mem->length \
m3MemAccessInBounds (operand, offset, sizeof (SRC_TYPE), _mem->length) \
)) { \
{ \
u8* src8 = m3MemData(_mem) + operand; \
Expand Down Expand Up @@ -1612,12 +1628,12 @@ d_m3Load_i (i64, i64);
d_m3Op (SRC_TYPE##_Store_##DEST_TYPE##_rs) \
{ \
d_m3TracePrepare \
u64 operand = slot (u32); \
m3_mem_addr_t operand = slot (u32); \
u32 offset = immediate (u32); \
operand += offset; \
\
if (m3MemCheck( \
operand + sizeof (DEST_TYPE) <= _mem->length \
m3MemAccessInBounds (operand, offset, sizeof (DEST_TYPE), _mem->length) \
)) { \
{ \
d_m3TraceStore(SRC_TYPE, operand, REG); \
Expand All @@ -1633,12 +1649,12 @@ d_m3Op (SRC_TYPE##_Store_##DEST_TYPE##_sr) \
{ \
d_m3TracePrepare \
const SRC_TYPE value = slot (SRC_TYPE); \
u64 operand = (u32) _r0; \
m3_mem_addr_t operand = (u32) _r0; \
u32 offset = immediate (u32); \
operand += offset; \
\
if (m3MemCheck( \
operand + sizeof (DEST_TYPE) <= _mem->length \
m3MemAccessInBounds (operand, offset, sizeof (DEST_TYPE), _mem->length) \
)) { \
{ \
d_m3TraceStore(SRC_TYPE, operand, value); \
Expand All @@ -1654,12 +1670,12 @@ d_m3Op (SRC_TYPE##_Store_##DEST_TYPE##_ss) \
{ \
d_m3TracePrepare \
const SRC_TYPE value = slot (SRC_TYPE); \
u64 operand = slot (u32); \
m3_mem_addr_t operand = slot (u32); \
u32 offset = immediate (u32); \
operand += offset; \
\
if (m3MemCheck( \
operand + sizeof (DEST_TYPE) <= _mem->length \
m3MemAccessInBounds (operand, offset, sizeof (DEST_TYPE), _mem->length) \
)) { \
{ \
d_m3TraceStore(SRC_TYPE, operand, value); \
Expand All @@ -1677,12 +1693,12 @@ d_m3Op (SRC_TYPE##_Store_##DEST_TYPE##_ss) \
d_m3Op (TYPE##_Store_##TYPE##_rr) \
{ \
d_m3TracePrepare \
u64 operand = (u32) _r0; \
m3_mem_addr_t operand = (u32) _r0; \
u32 offset = immediate (u32); \
operand += offset; \
\
if (m3MemCheck( \
operand + sizeof (TYPE) <= _mem->length \
m3MemAccessInBounds (operand, offset, sizeof (TYPE), _mem->length) \
)) { \
{ \
d_m3TraceStore(TYPE, operand, REG); \
Expand Down
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