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| author | Karol Herbst <karolherbst@gmail.com> | 2017-06-23 20:30:25 +0200 |
|---|---|---|
| committer | Ilia Mirkin <imirkin@alum.mit.edu> | 2017-07-21 23:45:18 -0400 |
| commit | c5cbb9a54345319d3924f9c7d0572fcc4739c516 (patch) | |
| tree | a7713169c78d5e2455c3a907f16403d68508301f | |
| parent | 4611343bcc05c75bcc9697243dabbb083f7078de (diff) | |
gallium/docs: add precise instruction modifier
v4: add comment about intermediate rounding step to MAD
Signed-off-by: Karol Herbst <karolherbst@gmail.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
| -rw-r--r-- | src/gallium/docs/source/tgsi.rst | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst index 6214de3df01..0dd2ac02401 100644 --- a/src/gallium/docs/source/tgsi.rst +++ b/src/gallium/docs/source/tgsi.rst @@ -26,7 +26,13 @@ each of the components of *dst*. When this happens, the result is said to be Modifiers ^^^^^^^^^^^^^^^ -TGSI supports modifiers on inputs (as well as saturate modifier on instructions). +TGSI supports modifiers on inputs (as well as saturate and precise modifier +on instructions). + +For arithmetic instruction having a precise modifier certain optimizations +which may alter the result are disallowed. Example: *add(mul(a,b),c)* can't be +optimized to TGSI_OPCODE_MAD, because some hardware only supports the fused +MAD instruction. For inputs which have a floating point type, both absolute value and negation modifiers are supported (with absolute value being applied @@ -237,6 +243,9 @@ This instruction replicates its result. .. opcode:: MAD - Multiply And Add +Perform a * b + c. The implementation is free to decide whether there is an +intermediate rounding step or not. + .. math:: dst.x = src0.x \times src1.x + src2.x |