GLSL: Fix #1591: Require the id in subgroupBroadcast to be constant.

Test/spv.subgroupBallotNeg.comp

@@ -0,0 +1,33 @@
+#version 450
+
+#extension GL_KHR_shader_subgroup_ballot: enable
+
+layout (local_size_x = 8, local_size_y = 8, local_size_z = 1) in;
+
+layout(binding = 0) buffer Buffers
+{
+    vec4  f4;
+    ivec4 i4;
+    uvec4 u4;
+    dvec4 d4;
+} data[4];
+
+void main()
+{
+    uint invocation = (gl_SubgroupInvocationID + gl_SubgroupSize) % 4;
+
+    uvec4 relMask = gl_SubgroupEqMask +
+                       gl_SubgroupGeMask +
+                       gl_SubgroupGtMask +
+                       gl_SubgroupLeMask +
+                       gl_SubgroupLtMask;
+
+    uvec4 result = subgroupBallot(true);
+
+    data[invocation].u4.x = subgroupBallotBitCount(result);
+    data[invocation].u4.y = subgroupBallotBitExtract(result, 0) ? 1 : 0;
+    data[invocation].u4.z = subgroupBallotInclusiveBitCount(result) + subgroupBallotExclusiveBitCount(result);
+    data[invocation].u4.w = subgroupBallotFindLSB(result) + subgroupBallotFindMSB(result);
+
+    data[invocation].f4.x   = subgroupBroadcast(data[0].f4.x,    invocation);  // ERROR: not constant
+}