gallivm: fix float->SNORM conversion

Just like the UNORM case we need to use round to nearest, not trunc.
(There's also another problem, we're using the formula for SNORM->float
which will produce a value below -1.0 for the most negative value which
according to both OpenGL and d3d10 would need clamping. However, no actual
failures have been observed due to that hence keep cheating on that.)

Reviewed-by: Jose Fonseca <[email protected]>

2 files changed, 47 insertions, 11 deletions

diff --git a/src/gallium/auxiliary/gallivm/lp_bld_conv.c b/src/gallium/auxiliary/gallivm/lp_bld_conv.c
index cbea966882a..56c15818e7c 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_conv.c
+++ b/src/gallium/auxiliary/gallivm/lp_bld_conv.c
@@ -257,6 +257,7 @@ lp_build_clamped_float_to_unsigned_norm(struct gallivm_state *gallivm,
       bias = (double)(1ULL << (mantissa - dst_width));
 
       res = LLVMBuildFMul(builder, src, lp_build_const_vec(gallivm, src_type, scale), "");
+      /* instead of fadd/and could (with sse2) just use lp_build_iround */
       res = LLVMBuildFAdd(builder, res, lp_build_const_vec(gallivm, src_type, bias), "");
       res = LLVMBuildBitCast(builder, res, int_vec_type, "");
       res = LLVMBuildAnd(builder, res,
@@ -742,7 +743,6 @@ lp_build_conv(struct gallivm_state *gallivm,
       }
       else {
          double dst_scale = lp_const_scale(dst_type);
-         LLVMTypeRef tmp_vec_type;
 
          if (dst_scale != 1.0) {
             LLVMValueRef scale = lp_build_const_vec(gallivm, tmp_type, dst_scale);
@@ -750,19 +750,37 @@ lp_build_conv(struct gallivm_state *gallivm,
                tmp[i] = LLVMBuildFMul(builder, tmp[i], scale, "");
          }
 
-         /* Use an equally sized integer for intermediate computations */
-         tmp_type.floating = FALSE;
-         tmp_vec_type = lp_build_vec_type(gallivm, tmp_type);
-         for(i = 0; i < num_tmps; ++i) {
+         /*
+          * these functions will use fptosi in some form which won't work
+          * with 32bit uint dst.
+          */
+         assert(dst_type.sign || dst_type.width < 32);
+
+         if (dst_type.sign && dst_type.norm && !dst_type.fixed) {
+            struct lp_build_context bld;
+
+            lp_build_context_init(&bld, gallivm, tmp_type);
+            for(i = 0; i < num_tmps; ++i) {
+               tmp[i] = lp_build_iround(&bld, tmp[i]);
+            }
+            tmp_type.floating = FALSE;
+         }
+         else {
+            LLVMTypeRef tmp_vec_type;
+
+            tmp_type.floating = FALSE;
+            tmp_vec_type = lp_build_vec_type(gallivm, tmp_type);
+            for(i = 0; i < num_tmps; ++i) {
 #if 0
-            if(dst_type.sign)
-               tmp[i] = LLVMBuildFPToSI(builder, tmp[i], tmp_vec_type, "");
-            else
-               tmp[i] = LLVMBuildFPToUI(builder, tmp[i], tmp_vec_type, "");
+               if(dst_type.sign)
+                  tmp[i] = LLVMBuildFPToSI(builder, tmp[i], tmp_vec_type, "");
+               else
+                  tmp[i] = LLVMBuildFPToUI(builder, tmp[i], tmp_vec_type, "");
 #else
-           /* FIXME: there is no SSE counterpart for LLVMBuildFPToUI */
-            tmp[i] = LLVMBuildFPToSI(builder, tmp[i], tmp_vec_type, "");
+              /* FIXME: there is no SSE counterpart for LLVMBuildFPToUI */
+               tmp[i] = LLVMBuildFPToSI(builder, tmp[i], tmp_vec_type, "");
 #endif
+            }
          }
       }
    }
@@ -860,6 +878,18 @@ lp_build_conv(struct gallivm_state *gallivm,
              for(i = 0; i < num_tmps; ++i)
                 tmp[i] = LLVMBuildFMul(builder, tmp[i], scale, "");
           }
+
+          /* the formula above will produce value below -1.0 for most negative
+           * value but everything seems happy with that hence disable for now */
+          if (0 && !src_type.fixed && src_type.norm && src_type.sign) {
+             struct lp_build_context bld;
+
+             lp_build_context_init(&bld, gallivm, dst_type);
+             for(i = 0; i < num_tmps; ++i) {
+                tmp[i] = lp_build_max(&bld, tmp[i],
+                                      lp_build_const_vec(gallivm, dst_type, -1.0f));
+             }
+          }
       }
     }
     else {
diff --git a/src/gallium/auxiliary/gallivm/lp_bld_format_soa.c b/src/gallium/auxiliary/gallivm/lp_bld_format_soa.c
index 114ce03bbdc..81cd2b0f7c6 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_format_soa.c
+++ b/src/gallium/auxiliary/gallivm/lp_bld_format_soa.c
@@ -39,6 +39,7 @@
 #include "lp_bld_gather.h"
 #include "lp_bld_debug.h"
 #include "lp_bld_format.h"
+#include "lp_bld_arit.h"
 
 
 void
@@ -221,6 +222,11 @@ lp_build_unpack_rgba_soa(struct gallivm_state *gallivm,
                double scale = 1.0 / ((1 << (format_desc->channel[chan].size - 1)) - 1);
                LLVMValueRef scale_val = lp_build_const_vec(gallivm, type, scale);
                input = LLVMBuildFMul(builder, input, scale_val, "");
+               /* the formula above will produce value below -1.0 for most negative
+                * value but everything seems happy with that hence disable for now */
+               if (0)
+                  input = lp_build_max(&bld, input,
+                                       lp_build_const_vec(gallivm, type, -1.0f));
             }
          }
          else if (format_desc->channel[chan].pure_integer) {