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nir: Fix ifind_msb_rev constant folding.

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For example if src0 is 0x80000000 we should return 1, not 0.

Signed-off-by: Georg Lehmann <dadschoorse@gmail.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>

Fixes: a5747f8ab3 ("nir: add opcodes for *find_msb_rev and lowering")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18951>
This commit is contained in:
Georg Lehmann
2022-10-10 13:56:51 +02:00
parent 125741dbae
commit 741dbadae0
1 changed files with 6 additions and 10 deletions
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16
src/compiler/nir/nir_opcodes.py
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@@ -500,16 +500,12 @@ for (int bit = bit_size - 1; bit >= 0; bit--) {
unop_convert("ifind_msb_rev", tint32, tint, """
dst = -1;
if (src0 != 0 && src0 != -1) {
for (int bit = 0; bit < 31; bit++) {
/* If src0 < 0, we're looking for the first 0 bit.
* if src0 >= 0, we're looking for the first 1 bit.
*/
if ((((src0 << bit) & 0x40000000) && (src0 >= 0)) ||
((!((src0 << bit) & 0x40000000)) && (src0 < 0))) {
dst = bit;
break;
}
/* We are looking for the highest bit that's not the same as the sign bit. */
uint32_t sign = src0 & 0x80000000u;
for (int bit = 0; bit < 32; bit++) {
if (((src0 << bit) & 0x80000000u) != sign) {
dst = bit;
break;
}
}
""")