llvmpipe: Fix random number generation for unit tests

We were never producing negative numbers for signed types.
Also fix only producing half the valid range for uint32, and
properly clamp signed values.

Because this now also properly tests snorm with actually negative
values, need to increase eps for such conversions. I believe these
cannot actually be hit in ordinary operation (e.g. if a snorm texture
is sampled and output to snorm RT, it will still go through snorm->float
and float->snorm conversion), so don't bother to do anything to fix
the bad accuracy (might be quite complex).
Basically, the issue is for something like snorm16->snorm8 that in the
end this will just use a 8 bit arithmetic right shift.
But the math behind it says we should actually do a division by 32767 / 127, which
is ~258, not 256. So the result can be one bit off (values have too large
magnitude), and furthermore, the shift has incorrect rounding (always rounds
down). For positive numbers, these errors have different direction, but
for negative ones they have the same, hence for some values the error will
be 2 bit in the end.

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=106232

diff --git a/src/gallium/drivers/llvmpipe/lp_test_conv.c b/src/gallium/drivers/llvmpipe/lp_test_conv.c
index 6e58a031515fac37978e6421fafa8399807e8eb3..a4f313a0bb3049ecda05f32017381c06a67d93de 100644 (file)
--- a/src/gallium/drivers/llvmpipe/lp_test_conv.c
+++ b/src/gallium/drivers/llvmpipe/lp_test_conv.c
@@ -211,6 +211,14 @@ test_one(unsigned verbose,
    assert(src_type.length * num_srcs == dst_type.length * num_dsts);
 
    eps = MAX2(lp_const_eps(src_type), lp_const_eps(dst_type));
+   if (dst_type.norm && dst_type.sign && src_type.sign && !src_type.floating) {
+      /*
+       * This is quite inaccurate due to shift being used.
+       * I don't think it's possible to hit such conversions with
+       * llvmpipe though.
+       */
+      eps *= 2;
+   }
 
    context = LLVMContextCreate();
    gallivm = gallivm_create("test_module", context);

diff --git a/src/gallium/drivers/llvmpipe/lp_test_main.c b/src/gallium/drivers/llvmpipe/lp_test_main.c
index 518ca274e7a31b5c1ee7266dabe95e29a7931cb0..5ec0dd347bd3edb1938718ea674ad5866dbf449e 100644 (file)
--- a/src/gallium/drivers/llvmpipe/lp_test_main.c
+++ b/src/gallium/drivers/llvmpipe/lp_test_main.c
@@ -147,6 +147,7 @@ write_elem(struct lp_type type, void *dst, unsigned index, double value)
       if(type.sign) {
          long long lvalue = (long long)value;
          lvalue = MIN2(lvalue, ((long long)1 << (type.width - 1)) - 1);
+         lvalue = MAX2(lvalue, -((long long)1 << (type.width - 1)));
          switch(type.width) {
          case 8:
             *((int8_t *)dst + index) = (int8_t)lvalue;
@@ -200,16 +201,24 @@ random_elem(struct lp_type type, void *dst, unsigned index)
       }
       else {
          unsigned long long mask;
-        if (type.fixed)
+         if (type.fixed)
             mask = ((unsigned long long)1 << (type.width / 2)) - 1;
          else if (type.sign)
             mask = ((unsigned long long)1 << (type.width - 1)) - 1;
          else
             mask = ((unsigned long long)1 << type.width) - 1;
          value += (double)(mask & rand());
+         if (!type.fixed && !type.sign && type.width == 32) {
+            /*
+             * rand only returns half the possible range
+             * XXX 64bit values...
+             */
+            if(rand() & 1)
+               value += (double)0x80000000;
+         }
       }
    }
-   if(!type.sign)
+   if(type.sign)
       if(rand() & 1)
          value = -value;
    write_elem(type, dst, index, value);