return err
	}

	// The RFC effectively limits promised requests to GET and HEAD:
	// "Promised requests MUST be cacheable [GET, HEAD, or POST], and MUST be safe [GET or HEAD]"
	// http://tools.ietf.org/html/rfc7540#section-8.2
	if opts.Method != "GET" && opts.Method != "HEAD" {
		return fmt.Errorf("method %q must be GET or HEAD", opts.Method)
	}

	msg := &http2startPushRequest{
		parent: st,

			s.vars[hashVar] = s.newValue1(zext, typs.Uintptr, h)

			// Load mask from cache.
			mask := s.newValue2(ssa.OpLoad, typs.Uintptr, cache, s.mem())
			// Jump to loop head.
			b := s.endBlock()
			b.AddEdgeTo(loopHead)

			// At loop head, get pointer to the cache entry.
			//   e := &cache.Entries[hash&mask]
			s.startBlock(loopHead)

  // CHECK-NEXT: %[[C1:.*]] = arith.constant 1 : index
  // CHECK-NEXT: %[[HEAD:.*]], %[[TAIL:.*]] = "shape.split_at"(%[[SHAPE1]], %[[C1]]) : (tensor<3xindex>, index) -> (tensor<1xindex>, tensor<2xindex>)
  // CHECK-NEXT: %[[SHAPEEQ2:.*]] = shape.cstr_eq %[[SHAPE0]], %[[HEAD]] : tensor<1xindex>, tensor<1xindex>
  // CHECK-NEXT: %[[SHAPEEQ:.*]] = shape.assuming_all %[[SHAPEEQ1]], %[[SHAPEEQ2]]

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