Prevent sinking coord calculation for sample (#3655)

The mark convergent pass is meant to prevent unwanted moving of
operations on derivative op input. It was previously only run on pixel
shaders. Because derivatives are supported in CS/MS/AS shaders as part
of shader model 6.6, it needs to be run on these stages for that target
too.

lib/HLSL/DxilConvergent.cpp

@@ -47,7 +47,8 @@ public:
 
   bool runOnModule(Module &M) override {
     if (M.HasHLModule()) {
-      if (!M.GetHLModule().GetShaderModel()->IsPS())
+      const ShaderModel *SM = M.GetHLModule().GetShaderModel();
+      if (!SM->IsPS() && (!SM->IsSM66Plus() || (!SM->IsCS() && !SM->IsMS() && !SM->IsAS())))
         return false;
     }
     bool bUpdated = false;

tools/clang/test/HLSLFileCheck/hlsl/objects/Texture/convergent_cs.hlsl

@@ -0,0 +1,48 @@
+// RUN: %dxc -E MainCS -T cs_6_6 %s | FileCheck %s
+// RUN: %dxc -E MainAS -T as_6_6 %s | FileCheck %s
+// RUN: %dxc -E MainMS -T ms_6_6 %s | FileCheck %s
+
+// Make sure add is not sunk into if.
+// Compute shader variant of convergent.hlsl
+
+// CHECK: add
+// CHECK: add
+// CHECK: icmp
+// CHECK-NEXT: br
+
+
+Texture2D<float4> tex;
+RWBuffer<float4> output;
+SamplerState s;
+
+void doit(uint ix, uint3 id){
+
+  float2 coord = id.xy + id.z;
+  float4 c = id.z;
+  if (id.z > 2) {
+    c += tex.Sample(s, coord);
+  }
+  output[ix] = c;
+
+}
+
+[numthreads(4,4,4)]
+void MainCS(uint ix : SV_GroupIndex, uint3 id : SV_GroupThreadID) {
+  doit(ix, id);
+}
+
+struct Payload { int nothing; };
+
+[numthreads(4,4,4)]
+void MainAS(uint ix : SV_GroupIndex, uint3 id : SV_GroupThreadID) {
+  doit(ix, id);
+  Payload pld = (Payload)0;
+  DispatchMesh(1,1,1,pld);
+}
+
+
+[numthreads(4,4,4)]
+[outputtopology("triangle")]
+void MainMS(uint ix : SV_GroupIndex, uint3 id : SV_GroupThreadID) {
+  doit(ix, id);
+}