Fix stdlib declarations for texture Gather() (#1510)

Fixes #1507

These operations were failing to take into account the way that array textures require an extra coordinate to be passed in for the primary location (but not the additional offsets). Adding `isArray` to the component count is the existing solution used for similar intrinsics elsewhere in the stdlib, and it is adopted here.

Because our test framework isn't really set up to do a lot of texture testing (including having no support for texture arrays), the test added here is just a cross-compilation test that compares output with fxc for comparable input.

1 files changed, 2 insertions, 0 deletions

diff --git a/tools/slang-test/slang-test-main.cpp b/tools/slang-test/slang-test-main.cpp
index 25aa13986..1144b4034 100644
--- a/tools/slang-test/slang-test-main.cpp
+++ b/tools/slang-test/slang-test-main.cpp
@@ -1732,6 +1732,7 @@ TestResult runCrossCompilerTest(TestContext* context, TestInput& input)
 
         switch (target)
         {
+            case SLANG_DXIL:
             case SLANG_DXIL_ASM:
             {
                 expectedCmdLine.addArg(filePath + ".hlsl");
@@ -1739,6 +1740,7 @@ TestResult runCrossCompilerTest(TestContext* context, TestInput& input)
                 expectedCmdLine.addArg("dxc");
                 break;
             }
+            case SLANG_DXBC:
             case SLANG_DXBC_ASM:
             {
                 expectedCmdLine.addArg(filePath + ".hlsl");