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-rw-r--r--src/util/half_float.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/src/util/half_float.c b/src/util/half_float.c
index 588f050d924..2eff2c84f51 100644
--- a/src/util/half_float.c
+++ b/src/util/half_float.c
@@ -215,7 +215,17 @@ uint16_t _mesa_uint16_div_64k_to_half(uint16_t v)
return v << 8;
/* Count the leading 0s in the uint16_t */
- int n = __builtin_clz(v) - (sizeof(unsigned int) - sizeof(uint16_t)) * 8;
+#ifdef HAVE___BUILTIN_CLZ
+ int n = __builtin_clz(v) - 16;
+#else
+ int n = 16;
+ for (int i = 15; i >= 0; i--) {
+ if (v & (1 << i)) {
+ n = 15 - i;
+ break;
+ }
+ }
+#endif
/* Shift the mantissa up so bit 16 is the hidden 1 bit,
* mask it off, then shift back down to 10 bits