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ppcopcodes: fix cntlzw with __builtin_clz.

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The result of __builtin_clz is undefined when the source operand
is zero. Add a check for this case and handle it accordingly.
This commit is contained in:
Maxim Poliakovski 2020-12-07 14:26:55 +01:00
parent 5cba9c1dae
commit 99641b1b5e
1 changed files with 3 additions and 3 deletions
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6
cpu/ppc/ppcopcodes.cpp
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@ -516,15 +516,15 @@ void dppc_interpreter::ppc_neg() {
void dppc_interpreter::ppc_cntlzw() { void dppc_interpreter::ppc_cntlzw() {
ppc_grab_regssa(); ppc_grab_regssa();
uint32_t lead = 0; uint32_t lead;
uint32_t bit_check = ppc_result_d; uint32_t bit_check = ppc_result_d;
#ifdef USE_GCC_BUILTINS #ifdef USE_GCC_BUILTINS
lead = __builtin_clz(bit_check); lead = !bit_check ? 32 : __builtin_clz(bit_check);
#elif defined USE_VS_BUILTINS #elif defined USE_VS_BUILTINS
lead = __lzcnt(bit_check); lead = __lzcnt(bit_check);
#else #else
for (uint32_t mask = 0x80000000UL; mask; lead++, mask >>= 1) { for (uint32_t mask = 0x80000000UL, lead = 0; mask; lead++, mask >>= 1) {
if (bit_check & mask) if (bit_check & mask)
break; break;
} }