Add GatherCmp* for texture objects (#3024)

The translation to GLSL is incomplete as intrinsics only exist for some combination of comparison and channel (just channel 0)

Closes https://github.com/shader-slang/slang/issues/3021

2 files changed, 65 insertions, 11 deletions

diff --git a/source/slang/core.meta.slang b/source/slang/core.meta.slang
index afb14dc4a..ddb81fd87 100644
--- a/source/slang/core.meta.slang
+++ b/source/slang/core.meta.slang
@@ -2176,50 +2176,83 @@ struct TextureTypeInfo
                 { 2, "Blue" },
                 { 3, "Alpha" },
             };
+            enum Cmp
+            { NotCmp,
+              Cmp
+            };
 
+            for(auto cmp : {NotCmp, Cmp})
             for(auto kk : kGatherComponets)
             {
+                auto samplerOrComparisonSampler = cmp == Cmp ? "SamplerComparisonState s, " : samplerStateParam;
+
                 auto componentIndex = kk.componentIndex;
                 auto componentName = kk.componentName;
 
                 auto outputType = cc.outputType;
 
+                const auto cmpName          = cmp == Cmp ? "Cmp" : "";
+                const auto cmpValueParam    = cmp == Cmp ? "float compareValue, " : "";
+                const auto cmpValueParamEnd = cmp == Cmp ? ", float compareValue" : "";
+                const auto supportsGLSL     = componentIndex == 0 || cmp == NotCmp;
+
                 EMIT_LINE_DIRECTIVE();
 
-                sb << "__target_intrinsic(glsl, \"textureGather($p, $2, " << componentIndex << ")\")\n";
-                if (base.coordCount == 2)
+                if(supportsGLSL)
+                {
+                    if(cmp == Cmp)
+                        sb << "__target_intrinsic(glsl, \"textureGather($p, $2, $3)\")\n";
+                    else
+                        sb << "__target_intrinsic(glsl, \"textureGather($p, $2, " << componentIndex << ")\")\n";
+                }
+                if (base.coordCount == 2 && cmp == NotCmp)
                 {
-                    // Gather only works on 2D in CUDA
+                    // Gather only works on 2D in CUDA without comparison
                     // "It is based on the base type of DataType except when readMode is equal to cudaReadModeNormalizedFloat (see Texture Reference API), in which case it is always float4."
                     sb << "__target_intrinsic(cuda, \"tex2Dgather<$T0>($0, ($2).x, ($2).y, " << componentIndex << ")\")\n";
                 }
                 if (isReadOnly)
                     sb << "[__readNone]\n";
-                sb << outputType << " Gather" << componentName << "(" << samplerStateParam;
-                sb << "float" << base.coordCount + isArray << " location);\n";
+                sb << outputType << " Gather" << cmpName << componentName << "(" << samplerOrComparisonSampler;
+                sb << "float" << base.coordCount + isArray << " location" << cmpValueParamEnd << ");\n";
 
                 if (isReadOnly)
                     sb << "[__readNone]\n";
                 EMIT_LINE_DIRECTIVE();
-                sb << "__target_intrinsic(glsl, \"textureGatherOffset($p, $2, $3, " << componentIndex << ")\")\n";
-                sb << outputType << " Gather" << componentName << "(" << samplerStateParam;
+                if(supportsGLSL)
+                {
+                    if(cmp == Cmp)
+                        sb << "__target_intrinsic(glsl, \"textureGatherOffset($p, $2, $3, $4)\")\n";
+                    else
+                        sb << "__target_intrinsic(glsl, \"textureGatherOffset($p, $2, $3, " << componentIndex << ")\")\n";
+                }
+                sb << outputType << " Gather" << cmpName << componentName << "(" << samplerOrComparisonSampler;
                 sb << "float" << base.coordCount + isArray << " location, ";
+                sb << cmpValueParam;
                 sb << "constexpr int" << base.coordCount << " offset);\n";
 
                 if (isReadOnly)
                     sb << "[__readNone]\n";
                 EMIT_LINE_DIRECTIVE();
-                sb << outputType << " Gather" << componentName << "(" << samplerStateParam;
+                sb << outputType << " Gather" << cmpName << componentName << "(" << samplerOrComparisonSampler;
                 sb << "float" << base.coordCount + isArray << " location, ";
+                sb << cmpValueParam;
                 sb << "constexpr int" << base.coordCount << " offset, ";
                 sb << "out uint status);\n";
 
                 if (isReadOnly)
                     sb << "[__readNone]\n";
                 EMIT_LINE_DIRECTIVE();
-                sb << "__target_intrinsic(glsl, \"textureGatherOffsets($p, $2, int" << base.coordCount << "[]($3, $4, $5, $6), " << componentIndex << ")\")\n";
-                sb << outputType << " Gather" << componentName << "(" << samplerStateParam;
+                if(supportsGLSL)
+                {
+                    if(cmp == Cmp)
+                        sb << "__target_intrinsic(glsl, \"textureGatherOffsets($p, $2, $3, ivec" << base.coordCount << "[]($4, $5, $6, $7))\")\n";
+                    else
+                        sb << "__target_intrinsic(glsl, \"textureGatherOffsets($p, $2, ivec" << base.coordCount << "[]($3, $4, $5, $6), " << componentIndex << ")\")\n";
+                }
+                sb << outputType << " Gather" << cmpName << componentName << "(" << samplerOrComparisonSampler;
                 sb << "float" << base.coordCount + isArray << " location, ";
+                sb << cmpValueParam;
                 sb << "int" << base.coordCount << " offset1, ";
                 sb << "int" << base.coordCount << " offset2, ";
                 sb << "int" << base.coordCount << " offset3, ";
@@ -2228,8 +2261,9 @@ struct TextureTypeInfo
                 if (isReadOnly)
                     sb << "[__readNone]\n";
                 EMIT_LINE_DIRECTIVE();
-                sb << outputType << " Gather" << componentName << "(" << samplerStateParam;
+                sb << outputType << " Gather" << cmpName << componentName << "(" << samplerOrComparisonSampler;
                 sb << "float" << base.coordCount + isArray << " location, ";
+                sb << cmpValueParam;
                 sb << "int" << base.coordCount << " offset1, ";
                 sb << "int" << base.coordCount << " offset2, ";
                 sb << "int" << base.coordCount << " offset3, ";
diff --git a/tests/cross-compile/glsl-texturegather.slang b/tests/cross-compile/glsl-texturegather.slang
new file mode 100644
index 000000000..125cf6df1
--- /dev/null
+++ b/tests/cross-compile/glsl-texturegather.slang
@@ -0,0 +1,20 @@
+//TEST:CROSS_COMPILE(filecheck=CHECK): -profile ps_5_0 -entry main -target glsl
+
+// CHECK: textureGather(sampler2DShadow(t_0,sc_0), (loc_0), (3.0))
+// CHECK: textureGatherOffset(sampler2DShadow(t_0,sc_0), (loc_0), (3.0), (off_0))
+// CHECK: textureGatherOffsets(sampler2DShadow(t_0,sc_0), (loc_0), (3.0), ivec2[]((off_0), (off_0), (off_0), (off_0)))
+// CHECK: textureGatherOffsets(sampler2DShadow(t_0,sc_0), (loc_0), (3.0), ivec2[]((ivec2(6, 6)), (ivec2(7, 7)), (ivec2(8, 8)), (ivec2(9, 9))))
+
+Texture2D t;
+SamplerState s;
+SamplerComparisonState sc;
+float4 main()
+{
+    const float2 loc = float2(1,2);
+    const float cmp = 3;
+    const int2 off = int2(4,5);
+    return t.GatherCmp(sc, loc, cmp)
+         + t.GatherCmp(sc, loc, cmp, off)
+         + t.GatherCmp(sc, loc, cmp, off, off, off, off)
+         + t.GatherCmpRed(sc, loc, cmp, int2(6,6), int2(7,7), int2(8,8), int2(9,9));
+}