[php-src] jit-arm64: Optimizing LONG MUL to SHIFT: add overflow detection for x86

Author: Hao Sun (shqking) Date: 2021-04-27T09:39:04Z Commit: https://github.com/php/php-src/commit/0be1cd9e279cc366bf2e2e8d1739b88633e054dc Raw diff: https://github.com/php/php-src/commit/0be1cd9e279cc366bf2e2e8d1739b88633e054dc.diff Optimizing LONG MUL to SHIFT: add overflow detection for x86 Similar to the AArch64 implementation, we compare "op" and "op << n >> n" to detect integer overflow. Note that instructions 'pushf' and 'popf' are used to save/restore the flags set by 'cmp', otherwise, the follow-up 'shl' might change the flags. Note that test case "mul_004.phpt" can pass now for x86. Change-Id: Ieee037f41dce298979b8a0964ca97598939c495c Changed paths: M ext/opcache/jit/zend_jit_x86.dasc Diff: diff --git a/ext/opcache/jit/zend_jit_x86.dasc b/ext/opcache/jit/zend_jit_x86.dasc index 8dbf12b94b5e..679746ec91e8 100644 --- a/ext/opcache/jit/zend_jit_x86.dasc +++ b/ext/opcache/jit/zend_jit_x86.dasc @@ -4180,6 +4180,7 @@ static int zend_jit_math_long_long(dasm_State **Dst, bool same_ops = zend_jit_same_addr(op1_addr, op2_addr); zend_reg result_reg; zend_reg tmp_reg = ZREG_R0; + bool use_ovf_flag = 1; if (Z_MODE(res_addr) == IS_REG && (res_info & MAY_BE_LONG)) { if (may_overflow && (res_info & MAY_BE_GUARD) @@ -4211,7 +4212,23 @@ static int zend_jit_math_long_long(dasm_State **Dst, | GET_ZVAL_LVAL result_reg, op1_addr | shl Ra(result_reg), floor_log2(Z_LVAL_P(Z_ZV(op2_addr))) if (may_overflow) { - // TODO: check overflow. + /* Compare 'op' and '((op << n) >> n)' for overflow. + * Flag: jne -> overflow. je -> no overflow. + */ + use_ovf_flag = 0; + | sar Ra(result_reg), floor_log2(Z_LVAL_P(Z_ZV(op2_addr))) + if (Z_MODE(op1_addr) == IS_CONST_ZVAL) { + | cmp Ra(result_reg), Z_LVAL_P(Z_ZV(op1_addr)) + } else if (Z_MODE(op1_addr) == IS_MEM_ZVAL) { + | cmp Ra(result_reg), [Ra(Z_REG(op1_addr))+Z_OFFSET(op1_addr)] + } else if (Z_MODE(op1_addr) == IS_REG) { + | cmp Ra(result_reg), Ra(Z_REG(op1_addr)) + } else { + ZEND_UNREACHABLE(); + } + | pushf + | shl Ra(result_reg), floor_log2(Z_LVAL_P(Z_ZV(op2_addr))) + | popf } } } else if (opcode == ZEND_MUL && @@ -4226,7 +4243,23 @@ static int zend_jit_math_long_long(dasm_State **Dst, | GET_ZVAL_LVAL result_reg, op2_addr | shl Ra(result_reg), floor_log2(Z_LVAL_P(Z_ZV(op1_addr))) if (may_overflow) { - // TODO: check overflow. + /* Compare 'op' and '((op << n) >> n)' for overflow. + * Flag: jne -> overflow. je -> no overflow. + */ + use_ovf_flag = 0; + | sar Ra(result_reg), floor_log2(Z_LVAL_P(Z_ZV(op1_addr))) + if (Z_MODE(op2_addr) == IS_CONST_ZVAL) { + | cmp Ra(result_reg), Z_LVAL_P(Z_ZV(op2_addr)) + } else if (Z_MODE(op2_addr) == IS_MEM_ZVAL) { + | cmp Ra(result_reg), [Ra(Z_REG(op2_addr))+Z_OFFSET(op2_addr)] + } else if (Z_MODE(op2_addr) == IS_REG) { + | cmp Ra(result_reg), Ra(Z_REG(op2_addr)) + } else { + ZEND_UNREACHABLE(); + } + | pushf + | shl Ra(result_reg), floor_log2(Z_LVAL_P(Z_ZV(op1_addr))) + | popf } } } else if (opcode == ZEND_DIV && @@ -4267,20 +4300,36 @@ static int zend_jit_math_long_long(dasm_State **Dst, int32_t exit_point = zend_jit_trace_get_exit_point(opline, 0); const void *exit_addr = zend_jit_trace_get_exit_addr(exit_point); if ((res_info & MAY_BE_ANY) == MAY_BE_LONG) { - | jo &exit_addr + if (use_ovf_flag) { + | jo &exit_addr + } else { + | jne &exit_addr + } if (Z_MODE(res_addr) == IS_REG && result_reg != Z_REG(res_addr)) { | mov Ra(Z_REG(res_addr)), Ra(result_reg) } } else if ((res_info & MAY_BE_ANY) == MAY_BE_DOUBLE) { - | jno &exit_addr + if (use_ovf_flag) { + | jno &exit_addr + } else { + | je &exit_addr + } } else { ZEND_UNREACHABLE(); } } else { if (res_info & MAY_BE_LONG) { - | jo >1 + if (use_ovf_flag) { + | jo >1 + } else { + | jne >1 + } } else { - | jno >1 + if (use_ovf_flag) { + | jno >1 + } else { + | je >1 + } } } }