[Mesa-dev] [PATCH v3 2/2] spirv: fix OpUConvert when the source is signed

[Samuel Iglesias Gonsálvez]

From: Iago Toral Quiroga <itoral at igalia.com>

In this case we don't want to do sign-extension, since the value is
interpreted as unsigned. If we want sign-extension, OpSConvert should
be used.

v2:
- Use src/dst bitsize to get the proper conversion opcode. (Jason)
---
 src/compiler/spirv/vtn_alu.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/compiler/spirv/vtn_alu.c b/src/compiler/spirv/vtn_alu.c
index 9dcd183a48d..e4b4fb5716f 100644
--- a/src/compiler/spirv/vtn_alu.c
+++ b/src/compiler/spirv/vtn_alu.c
@@ -349,7 +349,6 @@ vtn_nir_alu_op_for_spirv_opcode(struct vtn_builder *b,
 
    /* Conversions: */
    case SpvOpQuantizeToF16:         return nir_op_fquantize2f16;
-   case SpvOpUConvert:
    case SpvOpConvertFToU:
    case SpvOpConvertFToS:
    case SpvOpConvertSToF:
@@ -367,6 +366,18 @@ vtn_nir_alu_op_for_spirv_opcode(struct vtn_builder *b,
       nir_alu_type dst_type = nir_type_int | dst_bit_size;
       return nir_type_conversion_op(src_type, dst_type, nir_rounding_mode_undef);
    }
+
+   case SpvOpUConvert: {
+      /* SPIR-V expects to interpret the signed value as unsigned and
+       * not sign extend. Return the opcode accordingly.
+       */
+      unsigned src_bit_size = nir_alu_type_get_type_size(src);
+      nir_alu_type src_type = nir_type_uint | src_bit_size;
+      unsigned dst_bit_size = nir_alu_type_get_type_size(dst);
+      nir_alu_type dst_type = nir_type_uint | dst_bit_size;
+      return nir_type_conversion_op(src_type, dst_type, nir_rounding_mode_undef);
+   }
+
    /* Derivatives: */
    case SpvOpDPdx:         return nir_op_fddx;
    case SpvOpDPdy:         return nir_op_fddy;
-- 
2.14.1