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Avoid shift by 32 even if later masked, to avoid sanitizer warning (#4781). No functional change intended.

This commit is contained in:
Wilson Snyder 2023-12-30 14:46:57 -05:00
parent 2d7e8b58e4
commit 9de6612cde
1 changed files with 13 additions and 13 deletions
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26
include/verilated.cpp
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@ -465,27 +465,25 @@ WDataOutP _vl_moddiv_w(int lbits, WDataOutP owp, const WDataInP lwp, const WData
// Zero for ease of debugging and to save having to zero for shifts
// Note +1 as loop will use extra word
for (int i = 0; i < words + 1; ++i) { un[i] = vn[i] = 0; }
for (int i = 0; i < words + 1; ++i) un[i] = vn[i] = 0;
// Algorithm requires divisor MSB to be set
// Copy and shift to normalize divisor so MSB of vn[vw-1] is set
const int s = 31 - VL_BITBIT_I(vmsbp1 - 1); // shift amount (0...31)
const uint32_t shift_mask = s ? 0xffffffff : 0; // otherwise >> 32 won't mask the value
for (int i = vw - 1; i > 0; --i) {
vn[i] = (rwp[i] << s) | (shift_mask & (rwp[i - 1] >> (32 - s)));
}
vn[0] = rwp[0] << s;
// Copy and shift dividend by same amount; may set new upper word
if (s) {
for (int i = vw - 1; i > 0; --i) vn[i] = (rwp[i] << s) | (rwp[i - 1] >> (32 - s));
vn[0] = rwp[0] << s;
un[uw] = lwp[uw - 1] >> (32 - s);
for (int i = uw - 1; i > 0; --i) un[i] = (lwp[i] << s) | (lwp[i - 1] >> (32 - s));
un[0] = lwp[0] << s;
} else {
for (int i = vw - 1; i > 0; --i) vn[i] = rwp[i];
vn[0] = rwp[0];
un[uw] = 0;
for (int i = uw - 1; i > 0; --i) un[i] = lwp[i];
un[0] = lwp[0];
}
for (int i = uw - 1; i > 0; --i) {
un[i] = (lwp[i] << s) | (shift_mask & (lwp[i - 1] >> (32 - s)));
}
un[0] = lwp[0] << s;
// Main loop
for (int j = uw - vw; j >= 0; --j) {
@ -529,8 +527,10 @@ WDataOutP _vl_moddiv_w(int lbits, WDataOutP owp, const WDataInP lwp, const WData
if (is_modulus) { // modulus
// Need to reverse normalization on copy to output
for (int i = 0; i < vw; ++i) {
owp[i] = (un[i] >> s) | (shift_mask & (un[i + 1] << (32 - s)));
if (s) {
for (int i = 0; i < vw; ++i) owp[i] = (un[i] >> s) | (un[i + 1] << (32 - s));
} else {
for (int i = 0; i < vw; ++i) owp[i] = un[i];
}
for (int i = vw; i < words; ++i) owp[i] = 0;
return owp;