Support for reading low-bitdepth float formats in Blitter

Added support for reading the following formats in the Blitter:
- VK_FORMAT_B10G11R11_UFLOAT_PACK32
- VK_FORMAT_E5B9G9R9_UFLOAT_PACK32

Fixes all failures in:
[dEQP-VK.api.copy_and_blit.core.blit_image.all_formats.color]
.b10g11r11_ufloat_pack32.*
.e5b9g9r9_ufloat_pack32.*

Bug b/119620767

Change-Id: Ie5824b59b0193115cc7d142efc41cc3ac516c05c
Reviewed-on: https://swiftshader-review.googlesource.com/c/23348
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>

diff --git a/src/Device/Blitter.cpp b/src/Device/Blitter.cpp
index f7fca8d..5819ca4 100644 (file)
--- a/src/Device/Blitter.cpp
+++ b/src/Device/Blitter.cpp
@@ -328,6 +328,38 @@ namespace sw
                case VK_FORMAT_R16_SFLOAT:\r
                        c.x = Float(*Pointer<Half>(element));\r
                        break;
+               case VK_FORMAT_B10G11R11_UFLOAT_PACK32:
+                       // 10 (or 11) bit float formats are unsigned formats with a 5 bit exponent and a 5 (or 6) bit mantissa.
+                       // Since the Half float format also has a 5 bit exponent, we can convert these formats to half by
+                       // copy/pasting the bits so the the exponent bits and top mantissa bits are aligned to the half format.
+                       // In this case, we have:
+                       //              B B B B B B B B B B G G G G G G G G G G G R R R R R R R R R R R
+                       // 1st Short:                                  |xxxxxxxxxx---------------------|
+                       // 2nd Short:                  |xxxx---------------------xxxxxx|
+                       // 3rd Short: |--------------------xxxxxxxxxxxx|
+                       // These memory reads overlap, but each of them contains an entire channel, so we can read this without
+                       // any int -> short conversion.
+                       c.x = Float(As<Half>((*Pointer<UShort>(element + 0) & UShort(0x07FF)) << UShort(4)));
+                       c.y = Float(As<Half>((*Pointer<UShort>(element + 1) & UShort(0x3FF8)) << UShort(1)));
+                       c.z = Float(As<Half>((*Pointer<UShort>(element + 2) & UShort(0xFFC0)) >> UShort(1)));
+                       break;
+               case VK_FORMAT_E5B9G9R9_UFLOAT_PACK32:
+                       // This type contains a common 5 bit exponent (E) and a 9 bit the mantissa for R, G and B.
+                       c.x = Float(*Pointer<UInt>(element) & UInt(0x000001FF));         // R's mantissa (bits 0-8)\r
+                       c.y = Float((*Pointer<UInt>(element) & UInt(0x0003FE00)) >> 9);  // G's mantissa (bits 9-17)\r
+                       c.z = Float((*Pointer<UInt>(element) & UInt(0x07FC0000)) >> 18); // B's mantissa (bits 18-26)
+                       c *= Float4(
+                               // 2^E, using the exponent (bits 27-31) and treating it as an unsigned integer value
+                               Float(UInt(1) << ((*Pointer<UInt>(element) & UInt(0xF8000000)) >> 27)) *
+                               // Since the 9 bit mantissa values currently stored in RGB were converted straight
+                               // from int to float (in the [0, 1<<9] range instead of the [0, 1] range), they
+                               // are (1 << 9) times too high.
+                               // Also, the exponent has 5 bits and we compute the exponent bias of floating point
+                               // formats using "2^(k-1) - 1", so, in this case, the exponent bias is 2^(5-1)-1 = 15
+                               // Exponent bias (15) + number of mantissa bits per component (9) = 24
+                               Float(1.0f / (1 << 24)));
+                       c.w = 1.0f;
+                       break;
                case VK_FORMAT_R5G6B5_UNORM_PACK16:
                        c.x = Float(Int((*Pointer<UShort>(element) & UShort(0xF800)) >> UShort(11)));
                        c.y = Float(Int((*Pointer<UShort>(element) & UShort(0x07E0)) >> UShort(5)));
@@ -891,6 +923,8 @@ namespace sw
                case VK_FORMAT_R16G16B16_SFLOAT:\r
                case VK_FORMAT_R16G16_SFLOAT:\r
                case VK_FORMAT_R16_SFLOAT:
+               case VK_FORMAT_B10G11R11_UFLOAT_PACK32:
+               case VK_FORMAT_E5B9G9R9_UFLOAT_PACK32:
                case VK_FORMAT_A2B10G10R10_UINT_PACK32:
                        scale = vector(1.0f, 1.0f, 1.0f, 1.0f);
                        break;